# Could bacteria survive on a star?

If the right requirements are met, could bacteria survive on the Sun?

The bacteria would spend most of their time in hibernation and reproducing, and when the time comes, they spread out on plasma concentrations and fly towards the nearest celestial bodies.

• They are like water-bears and are nearly indestructible.
• They survive on radiation, through an extremely complex form of photosynthesis.
• This is probably the most appropriate place to say: "Not a snowball's chance in Hell!" :-) – ivan_pozdeev Jan 1 at 9:30
• What do you mean, "on a star"? Stars don't have a crust the way solid planets do. They just have diminishing distances from their center. By some definitions, the Earth is inside the Sun. – rumtscho Jan 1 at 16:54

## Some simple molecules can exist in stars - but not the right ones.

Contrary to popular belief, many different types of molecules can exist in stellar atmospheres, especially cool stars like red dwarfs. Some are even helpful spectral diagnostics; TiO bands are very common in stars cooler than 4000 K, which actually encompasses most of the stars in the galaxy, and thus serve as a possible surface temperature indicator, as they are dominant from 3000 K to 4000 K.

Now, many of these molecules - TiO, MgH, CaH - are simple inorganic molecules, and rather unhelpful for life. They may be useful as steps in chemical reactions, but those reactions require other molecules likely to dissociate under the typical conditions in stellar atmospheres. Of course, there are some simple hydrocarbons; CH comes to mind, lending its name to the CH stars. Though unlikely to help life survive on its own, it appears to be a part of a process for making more complex hydrocarbons - perhaps useful if ejecta into cooler portions of the interstellar medium, but not a stellar atmosphere.

## Amino acid dissociation

Let's talk about more complex organic molecules - the kind these bacteria would use. Amino acids are key compounds you might have heard of; 20 of them are used in protein. As you might expect, these amino acids are unstable even at reasonably low temperatures. Recent work on eight major amino acids concluded that they tend to break up around 200-300$$^{\circ}$$ Celsius, or roughly 500-600 Kelvin. That corresponds to atmospheric temperatures in some brown dwarfs, but it's substantially lower than the surface temperatures of the stars you're interested in. No amino acids mean that carbon-based life is a little bit unlikely - at least life as we know it.

## The building blocks of the building blocks of life

The majority of molecules used by carbon-based life are very likely to quickly dissociate, even in late-type red dwarfs - and so I think a simple answer to your question remains a no; these bacteria would be unable to survive. However, it is interesting to note that some stars may be able to form the building blocks of the building blocks of life. Polycyclic aromatic hydrocarbons (PAHs) remain a hot topic of research, and are extremely common the cosmos. It seems possible that they are formed in the atmospheres of carbon-rich stars, which then eject them into the interstellar medium. Given the right amount of time, and a bit of luck, it's possible that they could form the basis for complex interstellar molecules.

So perhaps you could find bacteria around stars, their constituent molecules created thanks to PAHs forged in a star's atmosphere. But the bacteria themselves certainly couldn't survive in such a hellish furnace.

• 20 amino acids are used in DNA? Maybe you mean 20 are used in proteins (ignoring selenocysteine and pyrrolysine), or that 4 nucleic acids are used in DNA? – forest Jan 1 at 12:06
• @forest You're quite right - thank you for the correction! – HDE 226868 Jan 1 at 15:34

Plasma is made by a soup of atomic nuclei and loose electrons.

As such no molecules exist in a plasma.

Life is based on (complex) molecules, therefore no life can exist in a plasma like the one present in stars. It's like trying to make a castle of cards in the middle of an hurricane.

• Correction: Many molecules exist in stellar atmospheres, particularly in cool and even Sun-like stars. Titanium (II) oxide is maybe the most well-known, the cause of key spectral bands in red dwarfs. So . . . I think your conclusion's right, but the reasoning is a little bit off the mark. – HDE 226868 Dec 31 '19 at 14:41