Can twin stars be born?

Although astronomers have considered this phenomenon in the past, the data indicates that this isn't how stars are born. That said, yes, your premise works.

Here's how you make a star, in a nutshell:

1. Take a big cloud of gas and dust.
2. Have the cloud grow until it reaches roughly the Jeans length, at which point the cloud is unstable.
3. Let some perturbation - perhaps a shock wave from a supernova or radiation from other stars - create a change in density and pressure.
4. The cloud should collapse into a protostar, a giant blob of gas that isn't quite the finished product.
5. Let the protostar contract via the Kelvin-Helmholtz mechanism until it gets hot enough to fuse hydrogen.

Voila! A star is born.

Binary star systems do exist. The leading theory for how they form is that fragmentation happens during the collapse of the cloud, meaning that it splits in two before a star begins to form. Each smaller collapsing cloud then forms a star, creating a binary system. Therefore, you can indeed have your "twin stars". The idea you're talking about resembles the so-called fission hypothesis (see section 2 here), where one protostar, early on, splits in two. There are quite a few problems with the idea, including features of the gas's compressibility. The fragmentation hypothesis is much more commonly accepted.

If you're looking for a more detailed overview of the topic, you may find this paper illuminating (pun intended).

posted about 7 years ago

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