This is more technical than what I usually post but it’s so fun and interesting that I couldn’t resist. This bizarre star opens up lots of cool questions. There are a few important details that you need to understand if you want to understand the linked articles (bear with me, it’s worth the effort!):
1) the outer layers of stars are not opaque. Stars are balls of compressed gas (compressed by their own gravity) and they are opaque, but only because they have so much gas. We can see through the thin outer atmosphere.
2) Unlike a cloud or fog, atoms in the outer atmosphere of a star shadow light at specific narrow bands of colors that vary from element to element. The more quantity of an element in the outer atmosphere the more dimming at its signature color. So, we can deduce the composition of a star element by element by measuring the dimming at a lot of different colors.
3) Because the star is opaque below the outer atmosphere, this trick for determining abundances doesn’t work for the interior of the star, so we need theories (and some assumptions) to approximate the overall composition of a star.
4) A common assumption is that most stars mix pretty well (largely due to convection) so the composition of the outer atmosphere is quite indicative of the overall composition But not for all stars and especially not for this star!
This star has some bizarre elements in its outer atmosphere, and the author presents some fascinating theories why that might be.