The Sun as Red Giant

[All Seeing Eye]

Earth is roughly 91,000,000 miles from the sun. I read somewhere that when the Sun turns to a Red Giant it will reach roughly as far out as Mars at most.
This means that even with the sun as a Red Giant the Moons of Jupiter will still be freezing cold. Jupiter alone would still be 332,000,000 miles from the sun.

The suns surface temp is 5,778 K.

How hot roughly would the surface of the sun be when in Red Giant form?

 

[DontFeedPhil]

That is an interesting idea. I have no idea but yeah, could our system turn into kryptons system? What planets might be habitable when that happens?

 

[Ronald Held]

How long from now or since the Sun started on the Main Sequence? Also remember that the Sun will lose mass and the main effect will be for the planets to slowly spiral outward.

 

[Neopeius]

Earth is roughly 91,000,000 miles from the sun. I read somewhere that when the Sun turns to a Red Giant it will reach roughly as far out as Mars at most.
This means that even with the sun as a Red Giant the Moons of Jupiter will still be freezing cold. Jupiter alone would still be 332,000,000 miles from the sun.

The suns surface temp is 5,778 K.

How hot roughly would the surface of the sun be when in Red Giant form?

At red giant stage, the surface temp will be 3-3600 K.

You have to remember that while the surface temperature will go down some, the surface area will increase enormously. So the luminosity will go up.

When the sun is at its maximum size (about 180x current radius), it will have a Luminosity of 3-5000x current. It will also have a mass of .6 suns.

So during those few thousand years that the sun is super big, and all the planets are 1.2x further away (assuming Periods stay the same and only radii increase--which isn't likely), theeeen...

even Neptune is going to be too hot to sustain life.

Source: http://articles.adsabs.harvard.edu/...GH&whole_paper=YES&type=PRINTER&filetype=.pdf

 

[mic of orion]

Earth is roughly 91,000,000 miles from the sun. I read somewhere that when the Sun turns to a Red Giant it will reach roughly as far out as Mars at most.
This means that even with the sun as a Red Giant the Moons of Jupiter will still be freezing cold. Jupiter alone would still be 332,000,000 miles from the sun.

The suns surface temp is 5,778 K.

How hot roughly would the surface of the sun be when in Red Giant form?

its all a guessing game, no scientist can tell you what 'll happen in 7 billion years time.

|IMHO Sun will increase in size with in next billion years anyways, increase to 1.5-1.8 million km diameter and this in turn will make life on earth impossibles, unless we move earth bit out 180-200 million km orbit.


Once sun does go super giant stage it might not be as some scientist are putting it.

Right now there are indications Sun will swell in to super giant stage and absorb only Mercury, leaving Venus and Earth out, you can see similar stuff happening to Alpha Century right now, Star is going through processes sun will go through in few billion years time. Once sun goes in to Giant/super giant stage it'll remain in that stage for millions of years (10-20 million at least) and than it'll shed most of its outer layers to form the planetary nebula.

This planetary nebula will give birth to a new star after. Same happened to Sirius B and will happen to Sirius A star in 1.2 billion years time. Vega as well...

PS, Just read that paper, yep I agree with much of it.

Just that I am not sure about the temperature being 3600kelvin. I think might loose more mass than what paper proposes, Alpha Century is interesting star to study, it is slightly older than sun at 6.5 billion years, it shows us what sun will be like in 2 billion years time.

 

[Ezri II]

Well if the sun turns into a red giant I will not have to worry about my heating bill.

 

[Ronald Held]

Venus and Earth should be consumed

 

[Christopher]

its all a guessing game, no scientist can tell you what 'll happen in 7 billion years time.

Prediction using a verified theory derived from concrete observations is not a guessing game. If I predict that an object dropped from a height of 19.6 meters will hit the ground 2 seconds later, that's not guesswork, it's calculation using a known and proven formula. There may be a slight margin of error due to air resistance or localized gravity variations, but the fundamental physical principle is anything but a guess, and it's a sure thing that the object will take very close to 2 seconds to hit the ground, not 1 second and not 20 seconds.

|IMHO Sun will increase in size with in next billion years anyways, increase to 1.5-1.8 million km diameter and this in turn will make life on earth impossibles, unless we move earth bit out 180-200 million km orbit.

I think you're confusing size with luminosity. It's the Sun's steady increase in luminosity which will render the Earth uninhabitable within 1-2 billion years.

Once sun does go super giant stage it might not be as some scientist are putting it.

Red giant, not supergiant. A star would have to be at least ten times as massive as the Sun to reach supergiant size.

Right now there are indications Sun will swell in to super giant stage and absorb only Mercury, leaving Venus and Earth out, you can see similar stuff happening to Alpha Century right now, Star is going through processes sun will go through in few billion years time.

What's your source for this claim? Both Alpha Centauri A and B are still comfortably in the Main Sequence; the system is only 1 to 3 billion years older than ours, and the A star should have roughly the same life expectancy as Sol, the B star significantly longer. I'm not aware of any reports suggesting that either star is anywhere near leaving the Main Sequence. And of course Proxima is so tiny that its MS life expectancy is on the order of a trillion years.

This planetary nebula will give birth to a new star after.

Not directly. Individual planetary nebulae lack the mass to collapse into stars on their own. Stars are formed in clusters out of much larger nebulae, dozens or hundreds at a time. Planetary nebulae will just continue to expand and dissipate until their material becomes part of the interstellar medium, and then portions of that medium will eventually become concentrated into nebulae which become stellar nurseries.

Same happened to Sirius B and will happen to Sirius A star in 1.2 billion years time. Vega as well...

Probably more like 7-800 million years or so for Sirius A, 650 million for Vega.

 

[Robert Treat]

Earth is roughly 91,000,000 miles from the sun. I read somewhere that when the Sun turns to a Red Giant it will reach roughly as far out as Mars at most.
This means that even with the sun as a Red Giant the Moons of Jupiter will still be freezing cold. Jupiter alone would still be 332,000,000 miles from the sun.

The suns surface temp is 5,778 K.

How hot roughly would the surface of the sun be when in Red Giant form?

At red giant stage, the surface temp will be 3-3600 K.

You have to remember that while the surface temperature will go down some, the surface area will increase enormously. So the luminosity will go up.

When the sun is at its maximum size (about 180x current radius), it will have a Luminosity of 3-5000x current. It will also have a mass of .6 suns.

So during those few thousand years that the sun is super big, and all the planets are 1.2x further away (assuming Periods stay the same and only radii increase--which isn't likely), theeeen...

even Neptune is going to be too hot to sustain life.

Source: http://articles.adsabs.harvard.edu/...GH&whole_paper=YES&type=PRINTER&filetype=.pdf

Earth is roughly 91,000,000 miles from the sun. I read somewhere that when the Sun turns to a Red Giant it will reach roughly as far out as Mars at most.
This means that even with the sun as a Red Giant the Moons of Jupiter will still be freezing cold. Jupiter alone would still be 332,000,000 miles from the sun.

The suns surface temp is 5,778 K.

How hot roughly would the surface of the sun be when in Red Giant form?

its all a guessing game, no scientist can tell you what 'll happen in 7 billion years time.

|IMHO Sun will increase in size with in next billion years anyways, increase to 1.5-1.8 million km diameter and this in turn will make life on earth impossibles, unless we move earth bit out 180-200 million km orbit.


Once sun does go super giant stage it might not be as some scientist are putting it.

Right now there are indications Sun will swell in to super giant stage and absorb only Mercury, leaving Venus and Earth out, you can see similar stuff happening to Alpha Century right now, Star is going through processes sun will go through in few billion years time. Once sun goes in to Giant/super giant stage it'll remain in that stage for millions of years (10-20 million at least) and than it'll shed most of its outer layers to form the planetary nebula.

This planetary nebula will give birth to a new star after. Same happened to Sirius B and will happen to Sirius A star in 1.2 billion years time. Vega as well...

PS, Just read that paper, yep I agree with much of it.

Just that I am not sure about the temperature being 3600kelvin. I think might loose more mass than what paper proposes, Alpha Century is interesting star to study, it is slightly older than sun at 6.5 billion years, it shows us what sun will be like in 2 billion years time.

By this time we should easily have been able to mine the gas giants for Helium-3 for thermonuclear spacecraft propulsion, and colonization of trans-Neptunian objects should enable us to ride out the sun's red giant and planetary nebula phases. Assuming, of course, that we don't first destroy our planet in a war or something like that.