Science fiction writers often benefit from using reality as a springboard. For science fiction, the weirder the bit of reality used, the better. As a public service, I offer a random selection of real astronomical items that are anomalous, suspicious, or downright odd. SF writers are encouraged to use these to brainstorm something interesting.
These are offered free of charge, I have no claim no them, no strings are attached.
For good examples of science fiction stories based around accurate astronomy, check out the free online anthology Diamonds in the Sky.
In the space environment, water is one of the most valuable things in the universe. You can split it into oxygen and hydrogen and use it for breathing, propellant, and in fuel cells. You can drink it or use it to grow plants and algae in your life support system. It can also be used to shield the crew from space radiation. However, as anybody who has carried a bucket of water knows, it has plenty of mass, which makes it very expensive to ship from Terra into orbit.
Which is why people planning space colonies are so interested in In-Situ Resource Utilization, which in this case is a fancy way of saying "trying to find an ice mine." It would be so much more convenient if the water was already there, so you didn't have to go to the insane expense of importing it.
The closest place to look is Luna. Unfortunately data from the Apollo moon missions suggested that the lunar regolith was drier than an old slab of concrete lying in the Sahara desert. Luna's "day" is 27 or so Terran days long, exposing Luna's surface to the merciless rays of the Sun and baking it to an oven-like temperature of 390°K. Any water-ice on the surface would have evaporated into space a long time ago. Even if an occasional water-ice comet smacked into Luna, the Sun's rays would make it go away.
But wait a minute. What if there were places on Luna that were permanently in shadow? Since there is no appreciable atmosphere, an area in Lunar shadow can drop down to a frigid 35°K. Any comet-ice that landed in such a deep-freeze would be preserved quite nicely.
The walls of lunar craters will provide shadow for part of the lunar day, but eventually the sun will be over head, the shadow will vanish, and the comet ice will evaporate. Except for at the lunar north and south poles. There the angle is steep enough that the sun's rays never penetrate the interior of the craters. See the picture, it shows the illumination of the lunar south pole over an entire lunar day. The dark areas are always dark. Any ice deposited there will still be there, patiently waiting for thirsty lunar colonists.
Lo and behold, it is there!
In In September 2009, India's Chandrayaan-1 space probe got a fleeting glimpse of lunar water-ice. In November 2009, NASA's LCROSS space probe watched as its spent upper stage violently crashed into the lunar south pole at 10,000 km/h, spotting ice crystals in the explosion. Finally in March 2010 the Chandrayaan-1 observed a bit of ice in the lunar north pole, a bit over 600 million tonnes of nearly pure water ice.
The lunar poles are going to be valuable real estate.
A solar eclipse is an awesome astronomical event. The historical record is full of people being stunned and shocked by eclipses, doing things like halting battles in progress. Historians love this, since it allows them to date any event that happened close to an eclipse down to the second.
There is Sol, blazing away in broad daylight, and suddenly Luna moves over it, until it perfectly covers it.
Perfectly ... covers ... it.
Waitaminute. Sol is something like 700,000 kilometers in radius, how the heck can Luna cover it? Sol is 400 times larger that Luna.
Ah, but Luna is about 400 times closer to Terra than Sol is, that makes it work.
Ummm .... waitaminute. Sol is x400 the size of Luna, and Luna just happens to be exactly x400 closer? Isn't that rather ... unlikely?
And just to make it weirder, Luna's orbit is steadily widening. It is moving further away from Terra at the rate of about 3.5 cm per year. Which means that Luna only fits more-or-less perfectly over Sol during 0.00006% of Terra's entire lifespan, and mankind just happens to be living during it.
A clever science fiction author could find all sorts of entertaining ways to use this. The obvious conclusion is that Luna did not randomly arrive at its current position. Somebody moved it there.
Lagrangian Points are orbital positions of peculiar stability that are formed with respect to two given planets, moons, suns, or any combination of the two. In other words, if you put a satellite or space colony in a Lagrangian point, it will tend to stay there. This lets you save on propellant for your attitude jets.
Points L1, L2, and L3 are only partially stable. That is, if you are exactly on the point you will stay there, but if you are nudged off point you will rapidly be flung away (it is possible to "orbit" these points instead of perching on them). L4 and L5 are much more desirable. If you are nudged off-point, you will tend to fall back into the stable position.
Please keep in mind that the L4 and L5 points are on an equilateral triangle. This means that since the distance between Terra and Luna is about 400,000 kilometers, this is the same distance as between the Terra-Luna L5 point and Terra, and between that L5 point and Luna.
You've probably encountered Lagrangian points in reference to Dr Gerard K. O'Neill's L5 orbital colonies. If your colony is a thirty kilometer long cylinder, you don't want it crashing into Luna or something.
In the orbit of Jupiter, the Jupiter-Sol L4 and L5 points are occupied by the Trojan Asteroids. There are other such clusters in the orbits of all other planets in the solar system, but they have nowhere near as many objects as the Trojans. This is due to the size of Jupiter and its proximity to the asteroid belt.
In Larry Niven's novel PROTECTOR, Jack Brennan discovers a valuable collectible piece of space history (a spent solid fuel rocket from Mariner XX) in Uranus's trailing Trojan point. Others have suggested that various Trojan points should be investigated to find hypothetical ancient alien artifacts. The theory is that since things tend to collect in Trojan points, it is worth examining such points to see if any anomalous objects are there. Duncan Lunan has a theory that an alien space probe from Epsilon Boötis is loitering in the Terra-Luna L5 point, but nobody takes him seriously.
Neutrino are exotic subatomic particles whose existence was deduced when physicists noticed that the subatomic event called beta decay didn't add up. Mother Nature always balances her books, the law of conservation of mass-energy forces that.
(Well, technically the Uncertainty principle allows one to embezzle mass-energy as long as you pay it back in the few nanoseconds before the cosmic accountant checks the ledger. But I digress.)
So with all nuclear reactions, the sum of all the starting particles mass-energy before the reaction must be exactly equal to the sum after. The problem with beta decay is that they weren't.
In 1930 physicist Wolfgang Pauli said "I've got it! What if beta decay produces some as-yet undiscovered weird invisible particle with properties that will exactly balance the books? We just thought things were not balancing because we couldn't see the blasted thing."
The other physicists rolled their eyes at Pauli. This sounded too much like your infant son telling you that he didn't break the lamp, it was an invisible green monster trying to frame him. Violates Occam's razor, that does.
Twenty-six years later Pauli was vindicated when Clyde Cowan and Frederick Reines finally managed to detect the weird invisible particle.
Why did it take them so long? Because neutrinos are real invisible. The slippery little devils can pass through about one entire light-year of solid lead before it hits a lead nucleus. They are beyond elusive, but can be detected by a sufficiently sensitive detector. These are typically 1,000 metric tons of ultra-pure water in a tank coated with photocells buried deep underground in an abandoned mine.
Since neutrinos are so darn penetrating, they can be used to observe astronomical objects. In 1987 a couple of neutrino detectors accidentally spotted a few from Supernova 1987A. The neutrinos arrived about two hours before the visible light of the supernova. This is because the neutrinos were created by the initial stellar core collapse, while the light was not created until two hours later when the shock-wave reached the star's surface. The important point is that neutrinos can be used to observe conditions inside the cores of stars.
Which leads to this Weird Astronomical.
In 1970 astrophysicists Raymond Davis, Jr. and John N. Bahcall figured they could use a neutrino detector to measure the rate of nuclear fusion in our primary star Sol. The Sun in our sky that gives us daylight. A single photon of light created by a fusion reaction in the core of Sol can take between 100,000 years and 50 million years to gradually work its way to the surface of Sol, then 8 minutes more to travel to Terra. But the slippery neutrino acts like the body of Sol ain't there. It takes a mere 2.3 seconds to reach the surface of Sol, and 8 minutes more to reach Terra.
This will allow a much more current report on the state of affairs at Sol's core. 2.3 seconds instead of 50 million years.
So Davis and Bahcall set up a 100,000 gallon tank of perchloroethylene 1,478 meters underground in the Homestake Gold Mine in Lead, South Dakota.
Bahcall had done the theoretical calculations on how many solar neutrinos would reach the detector. Davis used the detector to count the number of neutrinos that actually arrived. That's when all the fun started.
The trouble was that the actual number of neutrinos detected was consistently about one-third the number predicted by Bahcall's calculations. Now, keep in mind that such trouble in Science is actually a good thing. Isaac Asimov noted "The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' (I found it!) but 'That's funny ...'"
Properly following the dictates of the scientific method, the scientific community immediately declared that either Davis, Bahcall, or both had made a mistake. Both Davis and Bahcall double checked their work, but could find no errors.
The next step in the scientific method is for others to try and recreate the experiment and recreate the experimental results. Kamiokande in Japan, SAGE in the former Soviet Union, GALLEX in Italy, Super Kamiokande, also in Japan, and SNO (Sudbury Neutrino Observatory) in Ontario, Canada all tried it. Lo and behold, they got the same results. There were only one-third of the predicted amount of neutrinos coming out of Sol.
When you ask the question Why? is when things started getting edgy.
The two possibilities are: neutrinos are not understood as well as they thought or Sol is not understood as well as they thought. Or both.
The nuclear physicists shrugged, and promised to take a closer look and neutrino theory to see if there was anything they'd overlooked. If they found anything, particle physics would be updated with the new information. No big deal, science marches on and all that.
The solar astronomers started to sweat. The experimental results could mean that the rate of solar thermonuclear fusion had been drastically decreased by two-thirds. Which means the energy Terra receives from Sol could suddenly drop by two-thirds, at any moment from 50 million years in the future to eight minutes from now. The decrease would not be immediately apparent due to the 50 million year time lag of solar photons escaping the body of Sol. In that case the only question is how many millions of years in the past did the fusion rate stop?
Of course when the solar energy drops by two-thirds, Terra will die. Colder than a sno-cone in Niflheim.
Sir Arthur C. Clarke used this nifty situation as the background for his 1986 novel The Songs of Distant Earth. And there were a few popularization of science articles published with arresting titles along the lines of SCIENTISTS ARE UNSURE IF THE SUN WILL RISE TOMORROW.
Since way back in the 1970's the Standard Model of particle physics predicted that there were three kinds of neutrinos, ordinary garden-variety electron neutrinos plus the exotic muon neutrinos and tau neutrinos. Solar fusion produced electron neutrinos but none of the other two.
Clever readers will have already noticed the coincidence between the number of different neutrinos being three, and the neutrino detectors finding only one third of the expected number of solar neutrinos.
Back in 1957 Bruno Pontecorvo proposed the theory of Neutrino oscillation. It predicted that a neutrino of one type could spontaneously transmute into another type, then another type as it shot through space. This was an interesting conjecture, but it was not for decades that physicists could figure out an experiment which could detect this.
Finally several experiments did. Ironically one of them was was the data from the previously mentioned Sudbury Neutrino Observatory looking for solar neutrinos. As it turns out, most of the other neutrino telescopes could only detect electron neutrinos but not the other two kinds.
The Super-Kamiokande collaboration in Japan produced evidence strongly suggesting that it was seeing cosmic-ray created muon neutrinos transmuting into tau neutrinos.
But the SNO used heavy water as the detection medium. This allowed it to detect all three types of neutrinos. It could not distinguish between muon neutrinos and tau neutrinos, but it could see both. But it could distinguish between electron neutrinos and the other two. In 2001 it showed that 35% of the arriving solar neutrinos are electron neutrinos, with the others being muon- or tau-neutrinos (invisible to most neutrino detectors). Notice that 35% is quite close to one-third. If the muon- and tau-neutrinos represented solar fusion electron neutrinos that had transmuted, then the rate of solar fusion was as predicted, and all's well with the world. Sol is not going to unexpectedly go ppssssst!, turn dark, and condemn the world to an arctic death.
Alas, yet another thrilling science-fictional idea first offered by Science but then snatched away.
Sunspots are spots, on the Sun. They look like dark dots but they are only relatively dark. They are shining at about 4,200 °C (bright enough to blind you), it is just that the rest of the Sun is shining at 5,500 °C. So the spots are dark in comparison.
While they had been reported by Chinese astronomers thousands of years ago (there was a reference in the Book of Changes, c. 800 BC), the parochial self-centered powers that be in Europe could easily ignore reports of inconvenient truths from those heathen foreigners in distant lands. What had those blasted Chinese invented anyway that was worth anything? Well, besides paper, printing, gunpowder, the magnetic compass, and hundreds of others...
Unfortunately it was not quite so easy for the European PTB to ignore trouble-makers like Galileo, who had the audacity to invent scientific instruments that blatantly revealed the existence of things that the Church insisted did not exist. Like sunspots. A few other European scientists had seen and written about sunspots before Galileo did in the 1600s, but Galileo had a better PR department. Which meant it was Galileo who was brought up on charges before the Inquisition and threatened with an assortment of unspeakable tortures for doing stupid things like making the Church look like fools on subjects like the orbit of comets, spots on the Sun, and heliocentrism. Trifle with the infallibility of the Church at your own peril, fool.
European scientists still studied sunspots, but now they kept their mouths shut. Over the decades the records of scientific observations of sunspots gradually grew.
About two hundred years later in the late 1800s German Astronomer Gustav Spörer noticed something odd about the sunspot records. He wrote a paper about his findings in 1887. The British husband and wife team of astronomers Edward Maunder and Annie Maunder studied Spörer work and popularized it in a couple of papers of their own. Though criminally Annie Maunder's contributions were not recognized because being a male chauvinist pig was sadly widespread at the time (and shamefully still exists in the current day). For their work the phenomenon was named after the Maunders, which annoyed the Germans.
In the 1970s US astronomer John Eddy studied Spörer and the Maunder's work, and wrote a little paper about it. The paper wound up as the cover article in the June 1976 issue of Science magazine, and became a smash hit. John Eddy became famous, though he did have the kindness to popularize the effect under the Manuder's name instead of his own.
What is this effect? Why, the Maunder Minimum of course.
The sunspot records showed that the average number of sunspot rises and falls on a fairly regular 11 year cycle. Interesting but not earth-shattering.
Except for that disturbing 70 year gap from 1645 to 1715. Where there were no sunspots. At all.
And this was not just a gap in observations, there are records of the astronomers of the time pulling their hair out trying to figure out where all the blasted sunspots had gone..
This was only somewhat disturbing. The really awfully terrifyingly disturbing part is that the Maunder Minimum more or less corresponds to a particularly cold section in the middle part of the freaking Little Ice Age.
John Eddy identified another spotless period, 90 years from 1460 until 1550. He discovered it by analyzing carbon-14 in tree rings, since this pre-dated European astronomers keeping sunspot records. In a nice gesture he named it the Spörer Minimum. This period also corresponds to a particularly cold stretch of the Little Ice Age.
Other astronomers discovered the Dalton Minimum, lasting from 1796 to 1820 and also corresponding to a frigid part of the Little Ice Age.
Scientist are still bitterly divided over the connection, if any. There does not seem to be any direct mechanism between the number of sunspots and global temperatures. Occam's Razor suggests that the sunspots much affect solar output, but other scientists think it is just a coincidence or spotty data (which seems a little unlikely).
As a science fiction writer, the question becomes when will the next minimum occur, and what will happen then?
As mentioned above, with respect to space industrialization and colonization, water ice is one of the most valuable things in the universe. You don't want to haul it up Terra's horrific gravity well, you can get it for much less delta V cost from the Lunar poles.
However, there is another source with an even lower delta V cost: the Martian moon Deimos. Yes, the trip time is larger by about two orders of magnitude, but an entire kilometer per second of delta V savings is nothing to sneeze at.
Rob Davidoff and I worked up a science fiction background where the Martian moon Deimos becomes the water supplier for the entire solar system in our Cape Dread.
|delta-V for Transfers from LEO|
|Locale to LEO||LEO to Locale|
|Locale||delta-V||Trip Time||delta-V||Trip Time|
|Lunar Base||6.2 km/s||3 days||3.2 km/s||3 days|
|Deimos||5.6 km/s||270 days||1.8 km/s||270 days|
The rings of Saturn occasionally exhibit ghostly radial spokes that seemingly defy the laws of gravity. They were first spotted by the Voyager 1 space probe in 1980. When the Cassini space probe arrived in 2004, the spokes were absent, but they turned up in 2005. There are many theories about the spokes, but nobody knows for sure. They are thought to be electrically charged sheets of dust-sized particles but their source is unknown. Some say they are caused by meteors impacting the rings. Others say that lightning bolts in Saturn's atmosphere created electron beams that rake the rings. They do seem to be a seasonal phenomenon, occurring around the Saturnian equinox.
Back in the early 1980's, the Voyager space probe sent back some pictures of Saturn that had astronomers rubbing their eyes to ensure they were seeing properly. Apparently Saturn's north pole was surrounded by a jet stream in the shape of a hexagon. The Cassini space probe went by Saturn in 2007, and yes, the hexagon was still there. Apparently this was not a short-lived phenomenon (or the blasted hexagon can be turned off then on again). Scientists were annoyed, since hexagons are generally constructed by living creatures (like humans or bees) but you'd expect lots of different visible signs of native Saturnians besides a solitary hexagon. Granted there are some naturally occurring hexagonal crystals, but this thing on Saturn was composed of gas and was twice as wide as Terra.
But scientist were spared the necessity of postulating the existence of powerful space aliens turning Saturn into a titanic wargaming hex map by physicists Ana Claudia Barbosa Aguiar and Peter Read. They managed to reproduce the hexagonal flow pattern in a container of water. The effect seen is easy to create when a jet stream of fast moving fluid is inserted inside a slower spinning field. The ratio causes the polygons.
Having said that, the phenomenon is still suspicious. The jet stream composing the hexagon has to be maintained at a fairly constant speed. Any energy loss has to be replaced, and replaced pretty exactly. Not too much and not too little. And over a prolonged period of time. Hard to see how such precision can be maintained with natural causes.
The other suspicious aspect is the fact that not only does this seem to be unique to Saturn, it is unique to Saturn's north pole. If it was a natural phenomenon, you'd expect to see it in more places.
Saturn's moon Titan is the largest of the Saturnian moons. Indeed it is much larger than Luna. It is the only satellite known to have a dense atmosphere, and the only solar system object other than Terra where there is clear evidence of lakes.
Oh, did we forget to mention that on Titan it rains natural gas, the lakes are made out of petroleum, and the sand dunes are like coal? As a matter of fact, just the visible lakes of Titan are estimated to contain 300 times the volume of Terra's proven oil reserves.
Saturn's moon Iapetus looks like a giant walnut. Or like something formed in a giant mold, with a noticeable seam line. It is also suspicious that the ridge is precisely on Iapetus' equator. Iapetus is white on one side, and rock-colored on the other, with the ridge only on the rock side (though the white side does have a series of isolated mountain peaks along the equator). The ridge is about 1,300 kilometers long, 20 kilometers wide, and varies in height from 12 to 20 kilometers. The ridge does have lots of craters in it so it must be fairly ancient.
As always there are many theories but nobody knows for sure. Other than the UFO fans who are sure this is a second Death Star.
One theory holds that Iapetus was semi-molten due to the decay of aluminum-26 and had a rapid rotation of 17 hours. The rotation made Iapetus bulge at the equator. As Saturn's tidal forces braked Iapetus' rotation to the current 79 days, it cooled down fast enough to preserve the ridge bulge.
Another theory had that the ridge is an upwelling of icy material. If it was not along the equator, it would destabilize the moon's rotational axis. The Iapetus would wobble until the ridge was along the equator.
A third theory is that Iapetus originally had its own ring system, which would naturally have formed over the equator. As the ring material fell down, it would naturally fall on the equator.
Phil Plait is a famous astronomer, lecturer, and author. He runs the Bad Astronomy blog. When it comes to astronomy, he knows what he is talking about.
For a moon that is only 270 kilometers in diameter, it sure has lots and lots of craters. The craters are bizarre as well. The rims are sharp, the slopes are shallow, and the bottoms are flat. Astronomers are (pretty) sure this is because Hyperion is so un-dense that meteors do not blast out craters so much as they compress them (like sticking your finger into a block of Styrofoam). The result is quite strange, just look at the photo. Looks like a huge sponge.
Hyperion is one of the largest know object that is irregularly shaped (Proteus is the largest). If it was much larger, gravity would have crushed it into the shape of a sphere. Hyperion has a porosity of about 46%, which means it is less a solid moon and more a collection of rocks that happen to be flying in the same orbit.
And to top it off, its rotation is chaotic. Its axis of rotation wobbles so much that it is impossible to predict where it will be pointing at any given time. It wildly tumbles as it orbits around Saturn.
Everybody knows that the Asteroid belt is a bunch of huge rocks orbiting between Mars and Jupiter. This is true.
Everybody also knows that inside the belt it looks like Han Solo being chased by TIE fighters in the movie The Empire Strikes back. This is wrong. The average separation between asteroids is sixteen times the distance between Terra and Luna. If you were standing on a random asteroid, chances are you would not be able to see any other asteroids. Not without a telescope and an ephemeris.
In 1802, hypnotised by the seductive symmetry of the Titius-Bode Law, astronomer Heinrich Olbers suggested that the asteroid belt was the remains of a an exploded planet. Science fiction authors of the 1940's and 50's used this idea quite a bit, since it is incredibly awesome and cosmic. This is now commonly thought by astronomers to be false.
- The amount of matter required to explode and spread a planet around the belt would be, er, ah, astronomical.
- If you gathered all the asteroids together into one planet, the pathetic thing would be about 4% the size of Luna (3.2×1021 kg).
- The chemical composition of asteroids differ so wildly that it is difficult to explain how they come from the same planet.
Nowadays astronomers think the belt represents where Jupiter's gravity prevented a planet from being born.
There are 200 known asteroids with a diameter larger than 100 kilometers. There are approximately 0.7 to 1.7 million asteroids with a diameter larger than 1 kilometer.
Asteroid 16 Psyche is a weird one.
When it comes to the top most-massive asteroids, Psyche is right there at number 11. Blasted thing contains about 1% of the mass of the entire freaking asteroid belt. But that's not the weird part.
That space rock is no rock, it is almost 100% solid nickle-iron.
As a general rule, asteroids are not composed of just one substance like that. They are composed of many substances that are either [A] blended into a homogeneous mass or [b] large and hot enough to differentiate into layers of pure substances like an asteroidal rainbow gobstopper candy.
So how did Psyche get like that? The main theory is that it was once a cosmic rainbow gobstopper, but it got the snot beat out of it by multiple hit-and-run collisions with proto-planets. These collisions peeled off the outer rainbow layers, leaving only the nickle-iron core. The outer layers should be still nearby, but astronomers cannot find them. Perhaps they were long ago pounded into dust.
I'm sure a hypothetical deep space steel mill megacorporation in a hypothetical asteroid civilization will find Psyche to be the undisputed mother-load. And if there are more than one deep space steel mill megacorporation they will indisputably find Psyche worth fighting several wars over.
The core could have cooled off from the outside in or cooled off from the inside out. If the latter, Psyche could also be a titanic magnet. I'm sure evil science fiction authors can think of all sorts of diabolical plot complications using that little fact.
Before the Iron Age mankind did not have the technology to smelt iron from iron oxide ore. The only source of unoxidized metallic iron was from enstatite chondrite meteorites aka "thunderbolt iron". Telluric iron doesn't really count since it is only found in one deposit in the isolated island of Greenland.
If you lived in the Bronze age, you knew your flimsy bronze sword was no match for a hero wielding a legendary sword forged out of metal from a star. True, a meteoric iron sword is inferior to a modern-day steel sword, but against a bronze sword it might as well be made out of adamantium. Some researchers wonder if the advent of meteoric iron weapons gave rise to the myth of supernatural creatures only being vulnerable to "cold iron", but I digress.
As it turns out, most enstatite chondrites have been been spectrographically traced to have originated from 16 Psyche, planetoid of the meteor swords.
P/2010 A2 was initially thought to be a comet, since it had a tail. But after closer examination, it was noted that the tail was not composed of cometary ices, it was actually rock dust. And unlike all comets, the nucleus was not in the center of the dust halo. It wasn't even on the axis of the tail.
P/2010 A2 is now thought to be an asteroid about 150 meters in diameter that was struck by a smaller asteroid about one meter in diameter. Or this is a snapshot of a Klingon battle cruiser whizzing through the asteroid belt: you decide.
Researcher noticed that Asteroid P/2012 F5 had spat out four largish fragments, at suspiciously regular intervals. Then they noticed the blasted asteroid was spinning like a top (one rotation every 3.24 hours), easily fast enough to spontaneously break apart.
They had suspected this sort of thing happens, but this is the first time they caught it in the act. The two leading theories of why active asteroids emit fragments is either due to high spin rates or by collision with other asteroids. Asteroid P/2012 F5 is strong proof for the high spin rate theory.
The asteroid probably increase its spin rate due to the Yarkovsky effect, caused by uneven emission of thermal radiation. This generally only happens with asteroids smaller than 10 kilometers in diameter.
Horseshoe orbits occur when something small (like an asteroid) is in almost the same orbit as something large (like Terra). The orbit is only horseshoe shaped when plotted relative to the large body and the Sun (in the "rotating reference frame"). But it still is weird.
Saturn's moons Epimetheus and Janus occupy horseshoe orbits with respect to each other, but the ones SF authors will be interested in are the asteroids that have horseshoe orbits with respect to Terra. These include 54509 YORP, 2002 AA29, and most recently 2010 SO16. 2010 SO16 is unusual because it is exceedingly stable compared to the others. According to simulations it will probably be stable for at least the next 120,000 years, and maybe for more than a million years.
From the view point of 2010 SO16, it travels in its orbit, and eventually sees Terra approaching from the front (in the direction of motion). Terra will come quite close, then Terra will seem to reverse course and start to recede into the distance. About 175 years later, 2010 SO16 will see Terra coming close in the rear view mirror. Again Terra will come quite close, then suddenly seem to reverse course and start to recede. 175 years later the cycle repeats. 2010 SO16 never gets closer to Terra than about 50 times the distance between Terra and Luna.
From a science fiction author's viewpoint, you start with the absurdity of 2010 SO16 being so perfectly stable. Obviously some intelligent agency moved the asteroid into that orbit. Brainstorm the identity of the intelligence (secret super-scientific conspiracy, aliens, space creature disguised as an asteroid), the motive for the 175 year period, and you will be well on the way to having a nice background for your novel.
Haumea is a dwarf planet orbiting beyond Neptune's orbit. But this thing is not spinning like a top, no, it's spinning like a jet engine turbine.
Blasted planet rotates in a mere 3.9 hours, which is faster than any other known equilibrium body in the entire solar system, and faster than any known body larger than 100 kilometers in diameter. Spins so fast the planet is an ellipsoid twice as long as it is wide (1,920 × 1,540 × 990 km). Not bad for a planet with a mass of 4 × 1021 kilograms.
If you stood somewhere on Haumea's equator the centrifugal force from its rotation would almost entirely counteract its force of gravity. Reminds me of the planet Whirlygig from Charles Sheffield's Between the Strokes of Night
NASA's EPOXI space probe flew by comet Hartley 2 to do some observations of the hyperactive comet. The skittish thing was moving most erratically, which gave NASA a real challenge to intercept it with the space probe.
However, the probe did spot something extremely odd.
"...on its larger, rougher ends, the comet's surface is dotted with glittering blocks that can reach approximately 165 feet (50 meters) high and 260 feet (80 meters) wide. The block-like, shiny objects, some as big as one block long and 16 stories tall, appear to be two to three times more reflective than the surface average."
Astronomers are not as lucky as chemists or physicists. They can do experiments, astronomers cannot. A chemist can mix a few chemicals and see what happens, but an astronomer cannot, say, set Jupiter and Saturn on a collision course.
Or at least they couldn't before the invention of computer modeling. Using equations and lots of computer time, they can set Jupiter and Saturn on a collision course and see what happens.
This works marvelously for all sorts of astronomical questions. Until one tries to model the early evolution of our solar system. If you try to model a solar system like ours with four gas giants (Jupiter, Saturn, Uranus, and Neptune) when the simulation settles down, it does not look like our solar system. Not even close.
SwRI researcher David Nesvorny wrestled with this problem, and might have found a solution. Four gas giants won't work in the simulation. But five will. The simulation settles down into a something that remarkably resembles our solar system, and in the process the fifth planet is flung into interstellar space.
So if Dr. Nesvorny is correct, there is a primordial planet from the birth of the solar system in the abyss of deep space. And it is still out there. Waiting.
Oh, and did I mention that researchers from the University of Louisiana discovered that the spacing of comets in the Oort cloud is not as it should be? They calculate that this can be explained if there exists an as-yet undiscovered gas giant planet lurking in the fringes of the Oort cloud. Shades of the Nemesis theory!
Kapteyn's Star was considered to be a rather run-of-the-mill red dwarf star about 3.9 parsecs (12.8 light-years) away from Terra (though Jacobus Kapteyn was sufficiently impressed by its high proper motion that he named it after himself. It has the second highest proper motion after Barnard's Runaway Star).
Then astronomers discovered it was freaking old, 11.5 billion years old or a mere 2 billion years younger than the entire universe. Sol is only about five billion years old.
Its high proper motion, the fact it is moving retrograde, and its range of elemental abundances lead astronomers to conclude that it was originally part of Omega Centauri, the old dwarf galaxy that the Milky Way grabbed and gobbled up.
Kapteyn's Star 3.9 parsecs (13 light-years) away from Terra. But it was only 2.2 parsecs (7 light year) away a mere 10,800 year ago, about the time our Mesolithic ancestors were busy inventing agriculture.
Well, better Kapteyn's Star than Cthulhu's Star.
Scholz's star (full designation WISE J072003.20-084651.2) is a binary star system with a dim little spectral class M9 and an even dimmer T5 brown dwarf. It is currently about 17 to 23 light-years away.
But it wasn't always. About 70,000 years ago it came screaming past the solar system at about 80 kilometers per second, narrowly missing Sol by only 0.82 light-years (52,000 AU). While the stars proper only passed through the fringe of the Oort Cloud, their gravitation field probably perturbed every comet on this side of Sol.
Scholz's Star was within 100,000 AU of Sol for about 10,000 years. Unfortunately even at its closest it would have been far too faint to see (apparent magnitude of about 11.4, about 100 times fainter than the dimmest star visible to the naked eye). However M-dwarf stars often flare, so it might have been visible for periods of minutes to hours.
Comets perturbed from the Oort cloud will require roughly 2 million years to get to the inner Solar System. So you can expect a deadly hail of comets to plaster every planet in the system in about 1.93 million years.
Scholz's star passage probably did not have anything to do with the Population bottleneck that happened during the Toba Catastrophe, though both happened suspiciously at about the same time. It would be perfectly acceptable for a science fiction author to postulate a connection for the sake of their novel, since it is enough of an unbelievable coincidence that the author will have plenty of justification. Besides it might actually be true. There is a difference between "it is flat out impossible" and "scientists can think of no known mechanism which could cause it."
HIP 85605 is a star that (may be) currently 16.1 light-years from Sol. If that distance measurement is correct (which is a big if) in about 350,000 years (240,000 to 470,000) it will come plowing through the solar system and wreck the place.
Its closest approach to Sol will be from 0.13 to 0.65 light-years (8,200 to 41,000 AU), passing between the Oort Cloud and the Kuiper belt. This is going to savagely perturb every single comet in the Oort cloud and every asteroid in the Kuiper belt. In less than 2 million years the barrage of comets and asteroids will make every planet and moon in the entire solar system look like it has terminal acne and Terra's biosphere will suffer the mother of all mass extinctions.
Or maybe not. The distance of 16.1 looks suspiciously close to astronomers, it would fit the Hertzsprung-Russel diagram much better if it was about 200 light-years away. The distance was determined by the Hipparcos detector, which might have been confused by glare from a nearby star. If the latter distance is the correct one, HIP 85605 will never get closer to Sol than a very safe 30 light-years, and that in a remote 2.8 million years.
What has a spectral class of K7V, a mass of 60% of Sol, a velocity of 18.8 kilometers per second, and is heading straight at us? Why, the star Gliese 710, of course. But don't panic, it is about 19 parsecs away (62 light-years), so we won't have to worry for another 1.4 million years.
As nearly as the astronomers can calculate, Gliese 710 is not going to pass closer than about 0.88 light-year (0.27 ± 0.17 parsecs). This will send it right through the Oort cloud on the edge of the Solar System, sending a barrage of incoming comets. This will create results ranging from a mild 5% increase in cratering to extinction-level carpet bombing of every single planet and moon. Keep in mind that it will take about 2 million years for the perturbed comets to reach the inner Solar system, so the fun won't start until about 3.4 million years from now.
But the astronomers are not really sure since that is a long trajectory to calculate and they do not have much of a back trace. It is not impossible for Gliese 710 to actually penetrate the Solar system, passing within 1,000 AU of the Sun. Or even closer.
And in any event, the fact that Gliese 710 is aimed so closely at the Sun is quite suspicious. In his novel Eternal Light, author Paul McAuley suggests that the star was indeed aimed at the solar system by alien intelligences.
The weirdness is that the freaking planet is covered in red-hot ice.
There is plenty of water, but the planet's gravity smashes it into something called Ice X (ice-ten). Among its many amusing properties, it has a melting point of over 725°C.
Therefore, despite the fact that the planet's surface is broiling at about 439°C, the blasted ice refuses to melt.
This is because the primary star has an asteroid belt twenty times as dense as the one in our own solar system. Some estimates put it at one thousand times as bright as our zodiacal light, which would make the the Milky Way in the sky look about as bright as a half-dead firefly.
Of course such a dense asteroid belt means that in addition to nightly meteor showers, the planet will probably be at risk for Dinosaur Killer asteroid strikes on alternate Thursdays.
But it will be a big attraction for asteroid miners, looking for the mother load.
A simplistic analysis of its age leads one to believe it is 14.3 billion years old, which does not make sense since the universe is only 13.83 years old. Astronomers, after refining (i.e., fudging) their analysis now conclude it is 13.6 billion years old, or a mere 230 million year younger than the universe.
Since the Milky Way galaxy is only 13.2 billion years old, HD 140283 must have formed elsewhere and was later swallowed by our galaxy.
It is only 58 parsecs (190 light-years) away, which is far too close if it contains some eldritch cosmic horror from the dawn of creation.
KIC 8462852 is an unassuming spectral class F3 V/IV star approximately 454 parsecs (1,480 light-years) away. It seemed like just another run-of-the-mill class F3 star.
Until the Kepler Space Telescope started looking at it.
In an attempt to cope with the flood of data, the Kepler team took a tip from the Galaxy Zoo project and started an organization where civilian astronomy fans could comb through the data to find things that were quote "odd" unquote. Currently human beings are zillions of times better at spotting something odd than computer software, since it is almost impossible to explain to a computer what "odd" is. The Kepler team created the Planet Hunters
And like the Galaxy Zoo, the Planet Hunters project has paid off. In 2011 several members raised the alarm that the star KIC 8462852 was not just odd, it was downright bizarre.
The Kepler Space Telescope was designed to spot exoplanets, mainly by observing when a planet-sized object eclipses its parent star. Mature solar systems only have around ten planets or so, thus eclipses are rare events.
Immature solar systems are wall-to-wall asteroid belts slowly forming into planets, and thus have lots of eclipses. But you can spot immature solar systems by how brightly they shine at infrared. The asteroid belts engulf the entire system in a huge cloud of dust, which glows in the infrared band.
KIC 8462852 has lots of eclipses, but does not shine in infrared. This means it is a mature solar system (implying rare eclipses) that somehow has lots of eclipses.
What's more, eclipses by planets typically dim the star's light by under one percent. But from KIC 8462852 one of them was 15% and another was a whopping 20% ! A planet the size of Jupiter might dim the star by 1%, you'd need something about half the star's size to drop it 20%. Out of the 150,000 stars that the Kepler Space Telescope has observed, this is the only star with such an extreme light curve.
Even worse: the eclipses are aperiodic. Since eclipses are generally caused by an object orbiting something, they are by definition periodic: they happen at regular intervals. Aperiodic eclipses must be caused by a more complicated mechanism.
What the heck is going on?
In their paper T. S. Boyajian (who oversees Planet Hunters) and twenty-eight other people examined the possibilities. They studied and ruled out several scenarios: defects in Kepler, debris from an asteroid belt pileup, two planets colliding (like when Theia smacked into Terra and created Luna). None of them fit the facts.
Except for one. If another star passed through KIC 8462852 Oort cloud this would trigger a demolition derby of comets, which could explain the eclipses. As it turns out there is a small star about 1,000 AU away that could be the culprit.
The fly in the ointment is that such a comet smash up would have had to have happened within a short time span, about two years. The collision would have had to occur between observations from the WISE observatory and a large dip in flux (nearly 15%) seen in later Kepler observations. The chance that this happens just when we humans have telescopes to see it is literally astronomical.
Another fly in the ointment is that it is difficult to believe a swarm of comets could reduce the star's light by 20%.
Associate Professor of Astronomy and Astrophysics at Penn State Jason Wright is of the opinion that the long odds forces one to consider the dreaded "third-rail" of astronomy, the SETI hypothesis. In other words, he is not saying it is was aliens... but it was aliens.
Understand, Dr. Wright isn’t some wild-eyed crackpot; he’s a professional astronomer with a solid background.
SETI researchers have long suggested that we might be able to detect distant extraterrestrial civilizations, by looking for enormous technological artifacts orbiting other stars. Wright and his co-authors say the unusual star’s light pattern is consistent with a “swarm of megastructures,” perhaps stellar-light collectors, technology designed to catch energy from the star. Maybe even a Dyson Swarm under construction.
Dr. Wright said “Aliens should always be the very last hypothesis you consider, but this looked like something you would expect an alien civilization to build.” He and his associates are working on a paper, a pre-print can be found here.
Dr. Boyajian is now working with Dr. Wright and Dr. Andrew Siemion (UC-Berkeley) on a proposal to study KIC 8462852 at radio frequencies that could implicate the workings of a technological civilization.
Dr. Wright dubbed KIC 8462852 "Tabby's Star", after lead author Dr. Tabetha S. Boyajian.
Late breaking news, Dr. Bradley Schaefer looked at some historical data on KIC 8462852 and found more weird behavior. In his paper he details how the evidence from archival photographic plates circa 1890 to 1989 reveal that KIC 8462852 has been growing dimmer at the rate of 0.165±0.013 magnitudes per century. This is completely unprecedented for any F-type main sequence star.
This blows the comet theory right out of the water. The centuries long dimming and the recent dimming have to be due to one mechanism. For comets to do this would take an estimated 648,000 giant comets (each with 200 km diameter) all orchestrated to pass in front of the star within the last century. That ain't gonna happen, not naturally at any rate.
This has to be the result of some ongoing process with continuous effects. The SETI theory is getting harder and harder to avoid. Blasted thing might actually be a Dyson Swarm under construction after all.
The planet has the misfortune of being far too close to its parent star, only 0.01 AU away. By way of comparison, the solar system's innermost planet Mercury orbits at a healthy 0.39 AU. Mercury takes 88 days to orbit Sol, WASP-12b orbits its primary in only 26 hours.
WASP-12's gravitational tides are squeezing the planet into an egg-shape. The squeezing causes so much internal friction that the hot planet has inflated in size. The size has increases so much that the planet's gravity cannot hold it together. The star is sucking off the planet's surface at the rate of six billion metric tons per second. The material does not immediately fall into the star, instead it forms a ring which is gradually spiralling down to its doom.
At this rate the entire planet will be gobbled up in a mere ten million years. As usual, this sounds like a long time to a human being, but it is only about 1/500th the current age of Terra.
Back in 1968, Sir Arthur C. Clarke noticed something odd.
Before he wrote that article, he had used the idea in a short story called "Crusade" in 1968. In the story, something powerful and xenophobic is blowing up stars, and is gradually approaching Earth.
Erik Max Francis did an analysis with Mathematica. He pretty conclusively proves that the clustering in Aquila is due to the fact that it denotes an area of the sky that overlaps part of the galactic core. So there are more novae in Aquila because there are more stars of any kind in that general area.
This was a bit of speculation from Dr. David Brin that he wrote up in an article in the May 1984 issue of Analog magazine.
He used the (then current) data to infer that Earth suffered a mass extinction event with suspicious regularity, apparently happening every 197 million years (plus or minus 12 million years). There are no known natural terrestrial phenomenon that will happen with such regularity over such time scales. So he started examining astronomical phenomenon.
Sol (and Earth) takes 230 million years to orbit the center of the galaxy. This is close to 197 million years, but not close enough. But try postulating a Deadly Thing (such as a gamma ray burster or a large black hole with its radiation jets spraying the plane of the galaxy with glowing blue death) orbiting closer to the galactic center. If it orbits at a certain distance, the Sun will approach it every 197 million years. By taking reciprocals, you can determine that the Deadly Thing will have to have an orbit with a radius of 2.4 kiloparsecs (about 8,000 light-years). Sol has an orbit with a radius of about 10 kiloparsecs (about 33,000 light-years).
Just for the record, since Dr. Brin wrote his article, the new figure for the galactic orbital radius of Sol is 8.33 ± 0.35 kiloparsecs. So if you intend on using this in your novel you should recalculate appropriately.
As you would imagine, there are lots of questionable assumptions in this hypothesis. With these orbital radii, the closest the Deadly Thing ever comes to Earth is 7 kiloparsecs (about 23,000 light-years), so it has an unreasonably long range. It is also hard to imagine what could be so powerful and yet be undetectable by astronomers. Even more of a problem is that many scientist say there is no strong evidence for a regular occurrence of mass extinction events, and others have different values for the cycle length.
However, just because the assumptions are questionable does not mean they are wrong.
Regardless, this is still an excellent example of how starting with a few facts and interpolating using the laws of science can lead to entertaining results. SF authors are free to postulate other types of Deadly Things besides black holes, such as the Cthulhu star with its limited range telepathic death broadcast, or the Planet of Life-force Eaters With The Barely Long Enough Straw.
Rogue planets wandering the cold depths of space far from any star are very romantic in a science fictional sort of way. However, such planets are highly unlikely to contain life, unless said life forms enjoy living at a chilly 3°K.
But scientists Dan Hooper and Jason H. Steffen have an intriguing notion. One type of exotic particle (WIMPs) postulated as being behind the dark matter phenomenon would mutually annihilate other such particles, creating heat energy (i.e., WIMPs are their own anti-particle). WIMPs generally only rarely encounter each other, but they can be captured by the gravity of a planet. In the planet's core, WIMPs scooped up by the planet would quickly find other WIMPs and annihilate themselves, heating up the planet.
Hooper and Steffen calculate that since Terra is in a WIMP poor part of the galaxy WIMP annihilation would contribute a totally negligible one megawatt to Terra's heat. By contrast, Terra absorbs 100 quadrillion watts of heat from the Sun.
However, in the WIMP rich center of the galaxy, the heat goes up dramatically. They calculate that within 30 light-years of the galactic center, a planet with ten times Terra's mass could absorb enough WIMPs to generate 100 quadrillion watts. Thus such a rogue planet would be warm enough for life as we know it even with no sun nearby.
For people who take the long view, this would be ideal. A planet in a WIMP high region could be kept toasty warm for trillions of years, long after all the stars in the entire universe had burnt out.
A runaway star is young star, usually of spectral type O or early B, with an unusually high space velocity relative to the surrounding interstellar medium (on the order of 100 kilometers per second). If you trace its path backward, you will find the star cluster that it got ejected from. They generally occur when two binary systems pass too close to each other, or if the star has the misfortune to be orbiting a star that goes supernova. Such stars are not traveling fast enough to escape the gravitational pull of the galaxy.
The best known are Naos (Zeta Puppis), and the trio AE Aurigae, 53 Arietis, and Mu Columbae, all of which are racing away at 100 kilometers per second on diverging paths from a comparatively small region in the Orion nebula. They probably were orbiting the star that went supernova about two million years ago, forming Barnard's Loop.
CW Leonis (aka IRC +10216) is an elderly star about 120–150 parsecs away. But it is one of those runaway stars, since the blasted thing is streaking along at a good 91 kilometers per second. Please don't confuse it with CN Leonis aka Wolf 359, where Starfleet had the snot beaten out of it by a Borg Cube on stardate 44002.3.
In the image the star is hidden inside a sooty shell of gas about 84,000 AU in radius (0.4 parsec). The front edge of the shell forms the bow wake. In the image the star is moving from right to left.
The star is well on its way to becoming a white dwarf, as it blows off carbon-rich gas. Other than the fact it is moving as fast as a jack rabbit in front of a prairie fire, it is a pretty unremarkable star.
The poor innocent star had the misfortune to become an urban legend sometime in 2008.
Google Sky dumped lots of astronomical data into its sky view, to make it more interesting than just looking at white specks on a black background. Since CW Leonis is pretty much invisible by ordinary light, Google opted to use a false color infrared image. This used data from the IRAS infrared space telescope, which unfortunately had severe issues when it imaged the star. The innocent star became a huge ugly multicolored blob with two long tails that were scanning artifacts (basically lens flares).
Later in 2008 some clown who was either a True Believer conspiracy theorist or a troll in search of lulz went to WikiSky and labeled the object 'Nibiru'. Well, it is a wiki after all.
Nibiru is an imaginary planet that far too many credulous conspiracy theorists believe passes by Earth every 3,600 years, allowing the ancient astronaut god-like inhabitants to invade us in their flying saucers and enslave the entire human race. Thanks to that show-oaf on WikiSky throwing gasoline on the fire, to this day there are periodic outbreaks on conspiracy forums about how CW Leonis is comin' ta getcha and the end is nigh.
Hypervelocity stars are runaway stars that are traveling fast enough to escape the gravitational pull of the galaxy, typically on the order of 1,000 kilometers per second. All currently known hypervelocity stars are over 50,000 parsecs away from Earth.
Hypervelocity stars are probably created when a galactic core star suffers a close encounter with the Sagitarius A* supermassive black hole at the center of the galaxy.
SF authors can postulate that such stars are created by incredibly advanced aliens who like to travel. But there are implications. Consider, if there was a civilization powerful enough to accelerate their home star to 1000 km/sec; they must be running scared from something even more powerful.
Novae are stars that periodically explode, generally a white dwarf devouring hydrogen from a companion star and getting indigestion. They typically emit about 6 x 1037 Joules of energy, and our galaxy has about 30 to 60 Novae explosions per year.
Supernovae are much worse.
Unlike the periodic burp of a nova, a supernova destroys the entire star, leaving nothing but a neutron star or a black hole (actually, a type Ia supernova leaves behind nothing). A supernova typically emits about 1 x 1044 Joules (roughly ten million times as much as a nova) or more than all the other stars in the galaxy put together. That amount of energy is termed one FOE (ten to the Fifty-One Ergs), which is a unit of supernova strength.
You don't want one of these detonating anywhere near Earth, not if you care about the place. Scientists figure that a supernova explosion occurs within 10 parsecs of Earth every 240 million years or so. Possibly the most recent one was Geminga, which occurred about 300,000 years ago, and was probably the reason that Sol is near the center of a low hydrogen void called the Local Bubble.
Here is a handy-dandy list of supernova candidates which are due to explode anytime from several million years from now to this time tomorrow.
WR 104 is a Wolf-Rayet star, 2400 parsecs from Earth, and supernova candidate. Ordinarily that would be far enough away to be harmless. Unfortunately WR 104 just might be large enough to create a lethal gamma-ray burst. And there is some evidence that Earth is staring straight down WR 104's gun barrel, so to speak.
Gamma ray burst emerge along a supernovae's rotational axis. Astronomers measured WR 104's axis, and were nonplussed to discover that it was pointed within 16° of Earth. Right between the eyes. Later data suggested that the axis was only pointed within 30 to 40°, but they are still not sure.
Star MWC 922 is dying, and like many such stars it is spewing gas. But unlike many such stars, it is forming a rectilinear square. The theory is that it is emitting gas in two cones, with the cones being almost perfectly at ninety degrees to our line of sight.
Or we are watching a Kardashev type II civilization building a Dyson sphere. The rule of thumb is that almost all natural objects are curved, only artificial ones have square angles.
3C 397 (aka G41.1-0.3) is a galactic supernova remnant about 33,000 light-years away. It exploded between 2,000 and 1,000 years ago.
But as you can see, much like Red Square Nebula, the blasted thing has suspicious square angles in it. Is this another example of a Type II civilization playing Lego with supernovae? You decide.
The Sun has the misfortune to be located near the center of a huge region about 330 to 490 light-years in diameter called "The Local Bubble". The interstellar medium within the Local Bubble has a density of about 0.07 atoms/cm3, which is about ten times lower than in the rest of the galaxy. This makes a thin fuel source for a Bussard ramjet. The Local Bubble is thought to have been caused when the star Geminga went supernova about 300,000 years ago.
You see, the more astronomers studied Omega Centauri, the less it looked like a globular cluster. It is by far the largest of all of the Milky Way's globular clusters, about ten times as massive as all the other globular clusters. It does have an intermediate sized black hole in the core (4.0 × 104 solar masses). But the smoking gun is the population of stars it is composed of.
You see, apparently all globular clusters are formed at the birth of their parent galaxy, so all their stars are the same age, and all of them are metal poor. Since the stars of Omega Centauri are of wildly different ages and metallicities, most astronomers are sure it is not a globular cluster at all.
Instead, they have concluded that Omega Centauri is the core of a dwarf galaxy that the Milky Way galaxy grabbed and devoured several billion years ago.
A science fiction author could not help but wonder if some alien race living in the former Omega Centauri galaxy holds a grudge against the Milky Way galaxy, or considers the Milky Way a juicy vulnerable host organism Omega Centauri has infected. If either of these scenarios are true, the fact that Omega Centauri is about 4,840 parsecs (15,800 light-years) away is no comfort. You see, Kapteyn's Star was once a part of Omega Centauri, and that star is only 3.9 parsecs (13 light-years) away.
And Kapteyn's Star was only 2.2 parsecs (7 light year) away a mere 10,800 year ago, about the time our Mesolithic ancestors were busy inventing agriculture.
The Pistol Star is approximately 25,000 light-years from Terra in the direction of Sagittarius. Ordinarily a star at that distance would not be visible to the naked eye, were it not for the fact that the Pistol Star is about 1,600,000 times as luminous as Sol.
Well, actually you still can't see it with the naked eye because of all the interstellar dust clouds, but if it wasn't for all those pesky clouds the blasted thing is so luminous it would be a freaking fourth magnitude star. Even at a range of 25,000 light-years. The clouds defeated conventional telescopes but the Hubble Space Telescope finally spotted it in the early 1990's.
It radiates more energy in twenty seconds than our Sol does in an entire year.
The Pistol Star is a blue hypergiant and it currently the most luminous known star in the entire galaxy. It is expected to go kaboom as a supernova or hypernova real soon, at least as far as astronomical events go (one to three million years).
Charles H. Lineweaver, Yeshe Finner and Brad K. Gibson wrote an interesting paper entitled "The Galactic Habitable Zone and the Age Distribution of Complex Life in the Milky Way". Science 303 Issue 5654: 59-62 (January 2004). According to their analysis, if you are interested in regions of the galaxy where life as we know it can exist, there are good regions and there are bad regions. Specifically, the "Goldilocks zone" where life can develop is a torus shaped region centered on the galactic core. The inner edge is 7 kiloparsecs (23,000 light-years) from the core, and the outer edge is 9 kiloparsecs (29,000 light-years) from the core. Earth's sun Sol orbits right in the middle, at 8.33 ± 0.35 kiloparsecs (about 27,000 light-years).
Inside 7 kiloparsecs, the incidence of supernovae is so large that the radiation would fry any planets developing life. Outside of 9 kiloparsecs, there are not enough heavy elements to form any planets. So the galactic habitable zone is the only place where life as we know it can develop. At least according to the paper.
Keeping in mind that if one is dealing with life unlike we know it, all bets are off.
Sagittarius A* (pronounced "Sagittarius A-star") is an object visible by radio waves at the core of our own Milky Way galaxy. It is probably the accretion disc around the supermassive black hole which probably exists at the core as well. The presumed black hole is about 8,000 parsecs (26,000 light-years) away from us, and has a mass of about 4.1 million solar masses.
Unlike Sagittarius A*, we cannot actually see the black hole, because there is too much interstellar gas and dust in the way, along the spiral arms (yes, I know black holes are invisible because light cannot escape them, but the flood of space debris impacting the hole is not). But we are reasonably sure it is there. Astronomers have plotted the orbits of quite a few stars near the core, and determined that they are frantically orbiting something incredibly massive in the heart of Sagittarius A*. They can calculate the mass of the object, and its maximum radius, and the only possible natural object is a black hole. Possible artificial objects are left as an exercise for the reader.
The supermassive black holes at the cores of other galaxies are prone to emit large flares that last for several months. This is because about every 100,000 years the core black hole manages to pull in a hapless star close enough so it can be eaten. Astronomers have not seen Sagittarius A* flare like that, but one hundred thousand years is a long time between flares.
What they have seen are much smaller flares, which last only a few hours but occur daily. These are probably asteroids being consumed. And there was a larger flare about 300 years ago (inferred by the presence of a "light echo", nobody actually saw it happen). That flare was probably the death cry of a full sized planet.
Science fiction authors are free to speculate about a radiation-proof species of alien who have the misfortune to inhabit a planet spiralling into Sagittarius A*. They are likely to be all emo, angsty and depressed.
A team of astronomers lead by Rubab Khan stumbled over something strange in the Triangulum galaxy (M33) about three million light-years away. The object had been known about for decades, but was considered just another dim uninteresting object. They were shocked to discover that while it was quite dim in the visible light and near-infrared spectrum, in the mid-infrared spectrum the blasted thing is the most luminous object in the entire freaking Triangulum galaxy. Nobody had ever bothered to look at it in mid-IR before, because as a general rule things that are dim in the near-IR are also dim in the mid-IR. Looking back at old astronomical photographic plates, they know that whatever it is, it has been dim since at least 1949.
A gentleman who goes by the handle TME points out that an object that is very dim in the visible spectrum but unusually bright in the IR spectrum is the signature of a Dyson sphere. Freeman Dyson himself pointed out the possibility in his paper Search for Artificial Stellar Sources of Infrared Radiation, and proposed that SETI scientists should conduct a sky survey for such anomalous objects.
Object X probably is not actually a Dyson Sphere, but it is not totally impossible. It certainly is the closest thing spotted to date. Which is close enough for Science Fiction purposes.
The Sloan Digital Sky Survey took images of zillions of galaxies. So many that astronomers despaired at ever classifying them all. So they decided to enlist the help of civilians via the Galaxy Zoo project. Anybody could sign up, and do some simple classification of a few hundred galaxies. In most cases, the civilian volunteers were the first human beings to view the images.
This paid off, big time, in August of 2007. Hanny van Arkel, a Dutch school teacher, had been happily classifying galaxies for a few weeks. She classified IC 2497 as an anti clockwise spiral galaxy. Galaxy Zoo gave her a new galaxy, but she hesitated, then returned to the previous galaxy. IC 2497 was a spiral galaxy, but what in the universe was that green thing below it?
She asked on the Galaxy Zoo online forum and asked the other volunteers if they knew what it was. They didn't. As they discussed it, they started calling it "Hanny's Voorwerp", where voorwerp is the Dutch word for "object".
In January 2008, some of the real scientist behind the Galaxy Zoo got around to trying to identify Hanny's Voorwerp. They were flabbergasted to discover that they couldn't identify it either. University of Alabama astronomer Bill Keel said: "As far as we can tell, it's an unprecedented thing." Throughout the known universe "there is nothing else that's quite like it."
Naturally the voorwerp and the neighboring galaxy are the object of active astrophysical research, including a close in photo from the Hubble Space Telescope. The latest hypothesis is that it's the remnants of a small galaxy that was flash-illuminated by a quasar lurking in the core of IC 2497. But they are still not sure.
Late-breaking news: now that they know what to look for, astronomers have found eight more of the accursed things. In all the cases, the nearby quasar is not bright enough to illuminate the green goblin, for some as yet unexplained reason the quasar made a bright ultraviolet flash in the past. So the green goblin is fossil light. The actual green part is thought to be the remains of a smaller galaxy gobbled up by the quasar.
Everything seems to be on a collision course with everything else. Even our Milky Way galaxy and the Andromeda galaxy are due to collide in about three to five billion years. Some calculations suggest that there is a 50% chance that the Solar System will have its orbit altered so it is three times as far from the core, and a 12% chance that it will be ejected from the galaxy entirely.
But we won't care, because by that time the Sun will have swollen enough so that all the oceans of Earth will have evaporated.
Astronomer Noam Libeskind and his associates had just finished a long boring task of plotting the motions of most of the galaxies within 50 million light-years when they noticed something extremely odd.
The dwarf galaxies nearby the Milky Way galaxy, Andromeda galaxy, and the Centaurus A galaxy appear to be moving along a galactic superhighway. One that stretches from nearby our Milky Way galaxy all the way to the Virgo cluster of galaxies. Dr. Libeskind et al have concluded that there is a huge bridge of invisible dark matter at the center of the superhighway.
If so, this would explain a 40 year old astronomical conundrum. One would expect that all the dwarf galaxies astronomers can observe would be flying around randomly. But they are not. Instead they are mysteriously grouped into huge spinning planes.
The process of leaving a galactic superhighway of dark matter, exiting via an "off ramp" created by the Milky Way's gravity might be the cause of the dwarf galaxies forming into a spinning plane.
You can find more details in Libeskin's paper.
But any science fiction author worth their salt has already picked up on the terms "mysterious invisible dark matter" and "galactic superhighway", and their brain is buzzing with ideas about a secret method of intergalactic rapid transit.
This is M64, the "Sleeping Beauty" or "Black Eye" galaxy. At first glance, it looks like an ordinary run-of-the-mill spiral galaxy, 17 million light-years from Terra.
However, in 1994 astronomer Vera Rubin made the astonishing discovery that, unlike every other known galaxy, the interstellar gas in M64 is not rotating in the same direction that the stars are. Well, most of it. As it turns out, the gas within 3,000 light-years of the center rotates starwise, but freakishly the gas from 3,000 to 40,000 light-years rotates counter to the stars. And right at the edge between the two regions is an area of intense star formation, as the gas in the two regions collide and are compressed. All the stars there are young, blue, and incredibly hot.
Astronomers are pretty sure this counter-rotation is due to M64 colliding with a smaller galaxy millions of years ago. The smaller galaxy was long ago gobbled up, only the rotating gas remains.
Or...it could be a rather huge example of astroengineering done by an alien Kardashev type III civilization.
Astronomers want to know how far away various astronomical objects are, because otherwise you can't get any work done. Since we can't take a tape measure to the Andromeda galaxy, indirect methods have to be used.
In 1848 French physicist Hippolyte Fizeau noticed that the light from some stars was red-shifted. In 1912, Vesto Slipher discovered that practically all galaxies also had a red shift. And in 1929 Edwin Hubble formulated his famous Hubble's Law. The law basically said that by measuring a galaxy's red shift, you could calculate it's distance. A majority of astronomers were quite pleased. Now they could figure galactic distances.
However, the rest of the astronomers were quite angry.
You see, there are two major theories of cosmology: the Big Bang theory and the Steady State theory. Big Bang predicts that galaxies and other objects that are close to us will be different from those that are far away. Steady State on the other hand, predicts that they will be the same regardless of distance. If you arrange galaxies as if their distances were according to Hubble's Law, the close galaxies are different from the distant ones. Which should tell you the proponents of which theory were angry at Hubble's Law. There were other problems with the Steady State theory, but this problem was far to big to sweep under the carpet.
Desperate to salvage the Steady State theory, the proponents embarked on an all out effort to discredit Hubble's Law. And soon they discovered Stephan's Quintet.
They look like a nice group of five galaxies, wildly colliding with each other. They had been discovered in 1877, but the fun started in the 1960's when Geoffrey and Margaret Burbridge got around to measuring their red shifts. They all had a red shift indicating a distance of 340 million light-years or so. Except for NGC 7320, its red shift said it was at a distance of only 39 million light-years. So the other galaxies were ten times as far away, even though they appear to be interacting and therefore adjacent. Oops.
The Steady Staters started waving Stephan's Quintet like a bloody shirt, claiming it was proof positive that Hubble's law was baloney and Steady State was right after all. But other astronomers took a closer look at NGC 7320, re-examining the assumption that it was indeed associated with the other four. Yes, all the galaxies appear to be embedded in filaments torn from each other, but is it not possible that NGC 7320 is just a nearby galaxy that is upstaging the distant ones?
In 2000 the ironically named Hubble space telescope produced evidence that Hubble's law was correct after all, and the Big Bang theory was king. The telescope could resolve individual stars in NGC 7320, while the other galaxies were a distance-blurred mess. All main-stream astronomers accept the Big Bang theory, and Steady State has been relegated to the dust-bin of history.
But of course there are plenty of fringe people who still deny the evidence, as a cursory Google search will reveal. Any science fiction author who wanted to use Stephan's Quintet to overturn modern cosmology for plot purposes could find plenty of justification. Authors who want to pursue this further will find good material in the websites of Dr. Halton C. Arp which can be found here and here. (thanks to Rhys Taylor for those links)
There are two main types of galaxy: spiral and elliptical. Spiral galaxies are young virile galaxies, with plenty of stellar nurseries giving birth to new stars. Elliptical galaxies are tired old worn-out galaxies, composed of aging and ancient stars with no new stars being born.
Or at least that's what astronomers thought. Since this was common knowledge, nobody bothered to look. Astronomers studied all the light from a given elliptical galaxy at once, smearing together the light of all the individual stars into one spectrum.
Astronomers Alyson Ford and Joel Bregman were using Wide Field Camera 3 on the Hubble Space Telescope. This uses ultraviolet light, which just so happens to be capable of resolving individual stars in distant elliptical galaxies. They were quite startled to stumble over hot newly born stars and stellar nurseries in the decrepit old elliptical galaxy Messier 105. They are still trying to figure out where the heck the hydrogen is coming from. Elliptical galaxies have used up all their interstellar hydrogen. No hydrogen, no stellar nurseries.
Anyway, consider the inhabitants of such a galaxy. The old stars will be full of Kardashev type II civilization (aka "Star Gods") doing their darndest to become type III civilizations. Sprinkled here and there will be a small number of young stars, inhabited by primitive civilizations (like ours) cowering in a galaxy filled with Eldar Gods.
A Blazar is a species of Quazar which are the most powerful known objects in the entire universe. They are supermassive black holes in the cores of giant elliptical galaxies. As with all black holes, their incredibly powerful gravitational attraction sucks in any matter that gets too close. Some of it is swallowed, the rest is accelerated outward in two titanic beams of particles and intense radiation from the two poles of the black hole's rotational axis.
Astronomers are of the opinion that if neither beam is aimed at Terra we just don't see it, if it is aimed somewhat close to Terra we see a quazar, and if it is aimed straight at us we see a blazar. Quazars and blazars are all pretty much the same.
Except for Blazar OJ287. It is about 3.5 billion light-years away (and thus 3.5 billion years in the past), which is about average for quazars. It has a mass of 18 billion solar masses, the largest known, about six times larger than the runner-up. It has an eleven year periodic variation in its output which most astronomers agree is due to the fact that the black hole is actually two black holes in close orbit around each other. But none of those things are particularly strange.
What is strange is that there is Some Thing about 14 parsecs (about 49 light-years) from the binary black holes, right inside the radiation jet. How do we know it is there? Because the blasted thing is emitting cataclysmic flares of not visible light, not ultraviolet light, not even x-rays. No, it emits monstrous flares of gamma-rays. And astronomers are worried because they can't figure out what the heck it is.
Back in the 1980's a group of astronomers known as the "Seven Samurai" were quite startled to discover that there were a huge number of galaxies converging on a point about 250 million light-years away. There was nothing visible at the focus point, but all around it were galaxies madly colliding with each other and radiating large amounts of radio waves. The invisible object was dubbed "The Great Attractor". It had a huge mass (about 5.4 × 1016 solar-masses), and was apparently sucking in every galaxy within 200 million light-years or so, including our own.
This sort of fell apart in 2005. The Attractor falls into the part of the sky called the "zone of avoidance", meaning it is very difficult to observe since our own galaxy's spiral arms keeps getting in the way. But a later sky survey managed to do it, using improved equipment. As it turned out, the Great Attractor is still invisible and mysterious, but it has a mass that is only one-tenth the original estimate. Further: our galaxy is not being sucked into the Great Attractor. It is actually being sucked into an even more massive region beyond it called the Shapley Supercluster.
Imagine that you have a cyclic universe, where a universe is born in a big bang, ages, then finally dies in a big crunch. then it is reborn in a new big bang. The paper states that it is possible for some black holes born in one cycle to avoid being gobbled up in the big crunch, and would then be present in the new universe born in the next big bang. The black holes would be older than the new universe since they were born in the prior universe.
There was a second, unrelated paper that suggests that aliens can live inside black holes. That is, if you have a black hole that has an electrical charge and is rotating, in its interior (inside the inner Cauchy horizon) there are stable orbits a planet can occupy. In theory, highly advanced aliens could live on such planets, being unobservable from outside while exploiting the high energies and large time dialtions available. Not to mention the delicious possibilities of causality violations. Probably a Kardashev type III civilization. A pity they cannot escape.
Of course, they can escape if they have faster-than-light starships. The "surface" of a black hole is its event horizon. This is the point where the black hole's escape velocity is equal to the speed of light. Inside, the escape velocity is faster than light. Which presumably a faster-than-light starship is capable of. This makes an appearance in the Heechee novels of Frederik Pohl.
Anyway, Adam Crowl decided to combine these two papers. Imagine black holes older than the universe, containing aliens who are obviously also older than the universe. Elder godlike beings older than time, imprisoned in other dimensions. Oh my god, it's Cthulhu.
But that's OK. They cannot escape from inside the black hole. That is, of course, until some idiot in an FTL starships travels inside just to see whats there. I guess that's "when the stars are right".
(Actually this sounds more like the Cthulhu mythos elder god Yog-Sothoth who is coterminous with all time and space yet is supposedly locked outside of the universe we inhabit.)