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Questions tagged [red-giant]

Questions about red giants, large luminous low-mass stars in a late phase of stellar evolution.

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3 votes
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How long does it take a star to transition from main sequence to red giant?

I have read that it takes billions of years for stars of approximately the size of the Sun to get through the main sequence, after which it will enter the red giant phase. When that happens, how long ...
Johnny Dollard's user avatar
16 votes
3 answers
3k views

How would the sky look if Earth orbited a red giant at a safe distance?

Let's say that instead of the sun, we have a red giant, but are orbiting it at a safe distance, within the goldilocks zone. Would the sky actually look more red? Or would it be closer to white/...
Andrej Butić's user avatar
11 votes
2 answers
2k views

Could the Earth survive a red giant Sun?

So my question is that, is not a lie that we are flying away from the sun slowly, that is increasing by time because the sun loss mass, so when the scientist usually talk that we will get swallow by ...
Alberto Martínez's user avatar
9 votes
2 answers
3k views

How fast will the sun grow when it becomes a red giant?

We all know that our sun will become a red giant in a couple of billion years? But how fast will the process be when it starts? Would it be theoretically possible (disregarding the deadly effects of ...
klutt's user avatar
  • 191
22 votes
2 answers
5k views

Do we know a star that is similar to the Sun when it would be a red giant?

In about 5 billion years the Sun is predicted to become a red giant and have more than 200 times its current size, reaching a radius of about 5 AU when largest. I wonder what spectral class the Sun ...
user30007's user avatar
  • 1,236
19 votes
6 answers
12k views

Why do stars become red giants?

Disclaimer: I’m not a career astronomer. I don’t own a telescope. I have no professional credentials. But I do find this stuff fascinating, and I consume all the astronomy documentaries I can. ...
Zearin's user avatar
  • 293
18 votes
2 answers
2k views

When a star reaches the red giant phase, why does it become more opaque?

Please refer to this answer from Quora: ... a star will become a red giant before it begins burning helium. In fact, it will bloat into a red giant while still burning hydrogen in a shell on the ...
Ian Kemp's user avatar
  • 283
16 votes
4 answers
2k views

How can a red giant grow so big?

Supposedly when the sun becomes a red giant, it will grow big enough to swallow Earth. However, this requires the radius of the sun to expand by a factor of approximately 215×, meaning its volume ...
user541686's user avatar
7 votes
2 answers
339 views

Can a brown dwarf accrete enough mass from red giant to become a star?

Let's assume a brown dwarf is on orbit around a main sequence star. Than the star becomes a red giant. Let's assume the brown dwarf has "the right" orbit and can syphon matter from the red ...
Heopps's user avatar
  • 647
2 votes
1 answer
175 views

Does a red giant star produce more stellar wind than a yellow star?

Do red giant stars produce more stellar wind than when they were ordinary yellow stars? If so, how big a difference are we talking about?
Constantthin's user avatar
2 votes
2 answers
940 views

What would be the apparent magnitude of Betelgeuse if it were as close to Earth as Sirius?

How large and bright would Betelgeuse appear if it were as close to Earth as Sirius, before and after it goes supernova?
Justin Waters's user avatar
1 vote
1 answer
42 views

How do they see BOTH "anomalously cool with a significant mid-IR excess" rather than one or the other? (SN 2023ixf progenitor)

The abstract of the arXiv preprint SN 2023ixf in Messier 101: A Variable Red Supergiant as the Progenitor Candidate to a Type II Supernova (itself recently "discovered" in the observatory) ...
uhoh's user avatar
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1 vote
0 answers
56 views

Relation between initial mass and evolutionary phases lifetimes

Consider the following image (Source: An Introduction to Modern Astrophysics): There seems to be a relation between the initial mass/mass at the beginning of the MS and the time spent during ...
Hrsht's user avatar
  • 333
1 vote
1 answer
401 views

What exactly will happen when the Sun leaves the main sequence? I know it expands to a red giant twice, but what happens exactly? What's the timeline? [duplicate]

I've seen numerous claims surrounding this, with some claiming the expansion of the Sun from its end-main sequence radius to its peak red giant radius will take over 1 billion years, while others ...
Cryoraptor's user avatar
0 votes
0 answers
48 views

What are the primary astrophysical implications of a proposed mass of about 11 M⊙ for the SN 2023ixf progenitor?

The abstract of the arXiv preprint SN 2023ixf in Messier 101: A Variable Red Supergiant as the Progenitor Candidate to a Type II Supernova (itself recently "discovered" in the observatory) ...
uhoh's user avatar
  • 31.1k