I love it when scientists study an object I can truly sink my teeth into.
The image above is of RS Oph, a weird star some 5000 light years away. The star itself is in the center of those odd rings, and in fact it isn't an it, it's a they. It's actually a binary star, two stars orbiting each other. But neither star is normal. One, the primary (because it's brighter), is a red giant: an old star, maybe like the Sun will be in a few billion years. It's run out of hydrogen to fuse in its core, and as the core began to shrink it got hotter. The extra heat was dumped into the star's outer layers... and they responded as any gas does to extra heat: they expanded. So the star has puffed up. But all that extra surface area of the enlarged star means the ...
