Part 1 here. Honestly, astronomy is so filled with weird shit, this could be an infinite series.

Tabby’s star and friends. The last few decades have found plenty of exoplanets more or less by looking for wobble and periodic dimming of the star. As such that caused folks to do more widespread surveys looking for periodic dimming.  The project which organized this detected all kinds of cool exoplanets. Tabby’s star, discovered by Tabetha Boyajian, has a highly irregular dimming pattern for which nobody can give a decent explanation. A cool thing about astronomy is there is a lot of historical data kicking around nobody has had a look at as well, so they were able to find out that this has been going on for a long time by looking at antique photographic plates. Existing stellar theories do not account for this sort of fluctuation. Everything from dust rings to comet clouds to asteroid swarms to alien megastructures has been proposed to explain these weird variations, but nobody has the slightest idea what is going on. The most likely explanation (published by Miz Boyajian) is that it’s dust, but nobody really knows. This sort of thing is a lot of fun as it was really kind of an amateur thing. Corliss also noticed the general effect (AOF2) before this survey, and further ones have been detected over time. Wakipedia has a convenient list of some of them. The Random Transiter is a popular one that seems particularly odd. Speaking of which, the weirdest known star of them all:

Przybylski’s star. I ran across this looking at John Baez twatter feed for some reason (I think I was looking for something relating to his uncle). This star is also oddly variable. Worse, it is missing what you’d otherwise expect of iron and nickel in its composition due to its type. Solar models are sort of baseline facts for observational astronomy and all kinds of stuff is derived from them, so deviations from elemental composition are a big deal. Weirdest of all, it has all kinds of weird elements in it. Lots of rare earths which you never see in solar spectra; Przybylski himself discovered these. Worse, in 2008, some spectroscopists had a look and discovered all kinds of weird radioactive elements; including ones which are not supposed to exist in nature. These things are only supposed to exist in reactors or by merging neutron stars I guess (what are the chances of that happening?). It contains Einsteinium which has a half life of only 400-odd days. How does this happen? Some have speculated its weird motion and weird elemental composition could be explained by it having a neutron star nearby. Others suggest it is a garbage dump for an advanced alien civilization. Finally, the spectroscopists who discovered all those weird lines in Przybylski’s star might have been smoking crack. I think the wakipedia entry is fairly useless, but this series of blergs by Jason Wright  was pretty good.

 

Wolf Rayet stars (AOF4). These were considered  anomalous in Corliss’ time,  I guess they’re now considered a normal phase of stellar evolution in large stars, though I think that’s just because they’ve been around a long time. What makes them weird is they’re big, very high temperature and the emission lines of helium, carbon and nitrogen are broad, meaning there’s some large Doppler-shifting velocities going on in the photosphere. Maelstroms of high energy chaos. They’re an old discovery: 1867 by Charles Wolf and Georges Rayet (in Paris, lol; imagine astronomers discovering things in cities now). They’re also rare, meaning whatever they are, they are probably short lifespan objects. The accepted hand-wavey idea behind them is that they’re really big, have exhausted their core hydrogen and sort of semi-exploded leaving behind lots of helium and other fusion products. It could be considered a fizzled supernova, a stage towards supernova explosions, or a form of supernova which happens outside the visual spectrum. The first one blowing up into an actual supernova was detected just this year.

 

Anomalous Cephids (AOF6). Cephid variable stars are a common form of pulsating star which astronomers understand reasonably well and use for all kinds of handy things. They’ve been known about for hundreds of years, and are an important basis for figuring out distances of other objects and groups of stars in the universe. The mechanism is thought to be fairly well understood; it has something to do with the opacity of doubly excited helium. Some of the Anomalous Cephids have weird multi-frequency variations, and others have weird mass ratios compared to the ordinary run of Cephids.

Bright Carbon Stars Rarity (AOF8). Carbon stars themselves are pretty rare, but it seems odd that there aren’t more bright ones. The simple model is that a carbon star is an old and sickly red giant with more carbon than oxygen in the atmosphere due to changing internal reactions. You’d expect to see similar red giant to carbon star brightness ratios, but you don’t.

 

Impossible triple star KIC 2856960. I found this one in the fun catalog of anomalies called "the Breakthrough Listen Exotica Catalog" by some SETI guys. I don’t think it’s a particularly good candidate for SETI listening (nor are most of the other things they list), but it is kind of neat, and everyone loves lists. This one comes from the Kepler satellite data, just as Tabby’s star did, and there is no way for 3-stars to satisfy Newtonian physics and match the observed data. There is a weird way for a 4-star system to do so, but only if you have a weirdly resonant 4th body, the resonance of which can’t be detected. Not the weirdest thing in the world, but it’s an excuse to mention the BLEC reference which I may draw upon in a future. Lots of weird radio and gamma ray anomalies there. Plus they list other stars with odd elemental abundances (though none as weird as Przybylski’s star).