As both of your authors are away doing research over the summer (yes, of course, we’re both doing astro research), we haven’t had the time to post new and exciting blog posts for a while (not to mention the constant pile of schoolwork). Once we return, we’ll explain the research that we each did (or maybe astronomical requests if we get some!), but in the meantime, here’s a new post to satisfy your needs for astronomy knowledge.
Well, I guess we can’t say that rarity rocks since this is not a geology blog (unless the readers out there like that). But let’s get going about some rare stuff that’s out of this world! Yes, in the universe there are exotic, weird, and sometimes mind blowing objects that we shall explain in this post.
Exotic stars are technically defined as compact objects that are not made of electrons, protons, and neutrons and are in a degenerate state (those degenerates!). But to change things up we’ll also introduce some other weird objects. After all this is astronomy, when can we ever leave it simple? Mind you much of this is theoretical, so most people would be as confused as you or we are, but it’s interesting anyway.
To start, there are exotic stars. Please don’t scratch your head too much yet. But let’s make a list to explain:
- Quark and strange stars: If a neutron star manages to compress further, then just like with white dwarfs to neutron stars, they can compress into quark matter. This increases density, and a specific type is known as a strange star (strange, we know). They are made up of strange quarks (a specific type of quark…hopefully that wasn’t too quarky).
- Electroweak stars: Apparently in this case quarks can be turned into leptons by the electroweak force , which is what keeps electrons in orbit around a nucleus and allows for nuclear fission. They again arise when a quark star becomes denser.
- Preon stars: The next step in our evolution of this post. A bit more compact and a possible dark matter candidate. But there is some argument against their existence, though that applies to all of these objects in general, considering they are all theoretical.
- Boson stars: A boson is essentially a force. So as to not force you to take forever to read this, this star is somehow made of pure force (yes, the force is indeed strong with this one). They are also a possible dark matter candidate. Let’s not forget that they are theoretically transparent and in general would be difficult to detect.
In general, the stuff here isn’t necessarily normal. But what that’s not to say that black holes, pulsars, and anything we talk about in the future or past are not weird. We just wanted a post for these objects. Pretty much out of all of these so far the quark star is most likely (there are possible quark novae, most famously SN 2006gy). Now to name a few more astronomically odd objects.
This may also be relatively confusing, but there is also the dark star (it is made of dark matter, there is annoyingly another dark star). Dark matter interactions produces heat instead of normal fusion with matter. This is thought to form in the earlier universe and normal fusion wouldn’t occur because the dark matter collisions holding the star would prevent the normal matter in it from fusing.
Next up to confuse us all is the quasi-star. Another early universe star. These are thought to be black hole stars that are held by matter falling into a black hole. This could come from massive protostars to an extent collapsing into a black hole, but without outer layers being blown away. (The matter normally gets blown away and leaves a black hole with supernovae). These are associated with the theoretical population III stars that were the earliest stars in the universe.
There are also theories about how stars or degenerate objects can tidally capture each other. One possibility is the Thorne-Zytkow object (TZOs, we needed at least one new acronym, we know how you all missed them). This oddball consists of a giant star that manages to capture a neutron star that sinks to its core. So yes, a neutron star within a giant star (we’re hoping you have that nerdy astro moment where you go woah as well). Apparently the outer layers of the giant star can be shed such that a white dwarf core is left over, forming a binary system with the neutron star.
So how does any of this have to do with stellar evolution? To start, the exotic stars themselves serve as logical in-between phases from neutron stars to black holes. After all, with some room between the Chandrasekhar limit and the TOV limit then perhaps there could be some more room between when a star is pure neutron matter and when a star condenses far enough to become a black hole. Also, theoretical physics likes to make things more complex (because why not). In addition, there are many objects which astronomers just plainly have trouble explaining, like binary compact objects or the earliest stars.
So, as a final note from rvtau and astroisstellar, may your summer be quite…stellar. Also, thank you to anyone who keeps reading, we really appreciate it! Perhaps when we get back we’ll make some sort of anniversary type of thing.
Sources and links for further reading (links to images are below):
Carroll & Ostlie, An Introduction to Modern Astrophysics, 2nd edition, p. 691