Deneb Is a neat star. Most of the 30 brightest stars in the sky are bright because they're close to us. Not Deneb. (lemmy.dbzer0.com)

submitted 2 months ago by Melatonin@lemmy.dbzer0.com to c/casualconversation@lemm.ee

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Hey, my eye just captured some light that, depending on whose measurements are correct, is either as old as the Middle ages, or predates the Christian era.

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[-] Melatonin@lemmy.dbzer0.com 3 points 2 months ago

Yeah. It's big and bright and far. There's one other "naked eye" star that's further away, but it's a lot dimmer. Deneb is unique in a lot of ways.

Since 1943, its spectrum has served as one of the stable references by which other stars are classified.
Deneb is the prototype of the Alpha Cygni (α Cygni) variable stars, whose small irregular amplitudes and rapid pulsations can cause its magnitude to vary anywhere between 1.21 and 1.29.
Identifying whether Deneb is currently evolving towards a red supergiant or is currently evolving bluewards again would place valuable constraints on the classes of stars that explode as red supergiants and those that explode as hotter stars.
Deneb spent much of its early life as an O-type main-sequence star of about 23 M☉, but it has now exhausted the hydrogen in its core and expanded to become a supergiant.
It is one of the largest white 'A' spectral type stars known.

See for yourself!

https://en.wikipedia.org/wiki/Deneb?wprov=sfla1

[-] mossy_@lemmy.world 2 points 2 months ago

Wait how would a star "evolve bluewards again"? I thought when a star fuses all of its smaller elements into heavier ones, it's a one way trip

[-] Melatonin@lemmy.dbzer0.com 2 points 2 months ago

Recent stellar evolution computations show that the blue supergiant (BSG) stars could come from two distinct populations: a first group arising from massive stars that just left the main sequence and are crossing the Hertzsprung–Russell diagram (HRD) towards the red supergiant (RSG) branch, and a second group coming from stars that have lost considerable amount of mass during the RSG stage and are crossing the HRD for a second time towards the blue region.

[-] mossy_@lemmy.world 2 points 2 months ago* (last edited 2 months ago)

Wow. This goes well beyond "casual conversation" 😅

But your article is saying that it happens, and a large factor is mass being ejected, and I can understand that I suppose. Cool!

[-] Melatonin@lemmy.dbzer0.com 2 points 2 months ago

Well...

I started casual...

this post was submitted on 25 Mar 2025

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