The Universe is: Expanding, cooling, and dark. It starts with a bang! #Cosmology Science writer, astrophysicist, science communicator & NASA columnist.
The hottest stars in the Universe are all missing one key ingredient
Want to be hotter? Add more mass. Want to go even hotter than that? Lose almost all of it.
“A candidate is not going to suddenly change once they get into office. Just the opposite, in fact. Because the minute that individual takes that oath, they are under the hottest, harshest light there is. And there is no way to hide who they really are.” -Michelle Obama
In astronomy, there’s a simple formula for stars: add more mass, and your star becomes brighter, bluer, and hotter.
This pattern hold from stars just a few percent the mass of the Sun to over 200 times as massive.
But there’s a limit to the temperature these stars achieve, even the most massive ones.
If you want to go hotter, you need something extra: to lose your hydrogen.
As the most massive stars evolve, they burn through their core’s fuel, expanding into a red giant and fusing helium.
Normally, this progresses into even heavier elements: carbon fusion, then oxygen, and so on.
But in a special stellar class — Wolf-Rayet — the outer hydrogen layers get blown off, leaving only heavier elements behind.
With strongly, multiply ionized atoms of carbon, nitrogen, and oxygen in their atmospheres, these stars are the hottest known.
Largely at only be 10-to-20 times the Sun’s mass, they burn at up to 200,000 K, emitting hundreds of thousands of times the light of the Sun.
Only a few of them are visible to the naked eye, as most of this energetic radiation is ultraviolet, not visible.
Only ~1,000 Wolf-Rayet stars populate the entire Local Group.
Mostly Mute Monday tells the story of an astronomical objects, class, or phenomenon in images, visuals, and no more than 200 words.