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Fraser
2005-Mar-29, 06:50 PM
SUMMARY: After a long life, most sun-like stars grow into red giants once they've depleted most of their hydrogen fuel. The relatively small region around the star which is just at the right temperature to support liquid water will extend as the red giant expands. This means that previously frozen planets (like Mars) could thaw out and life might have a second chance to happen in a solar system. There are currently 150 red giant stars within 100 light-years of the Earth, and many of these could be a place to search for life in addition to main-sequence stars similar to our own Sun.

View full article (http://www.universetoday.com/am/publish/dying_stars_second_chance.html)

What do you think about this story? Post your comments below.

lswinford
2005-Mar-29, 07:15 PM
But how long is that window of opportunity? After phasing out into the red giant stage, how long would that be a stable situation? What of the intervening stages, wouldn't they essentially cauterize Mars during the expansion? I suspect there might be windows of opportunity for expanding civilizations (ala a Star Trek-type distant future), but would there be time for life to develop, if the commonly accepted pattern of earth's life were repeated on Mars?

BTW: as I recall reading the book, a few years back, Planet of the Apes was set on a habitable planet around a certain red giant in Orion.

antoniseb
2005-Mar-29, 07:34 PM
This is a topic that has been discussed quite a bit here in the UT forum. On the big scale of things, it seems odd that when we look at the star being on the main sequence for billions of years that we'd seek refuge on a former frost-ball planet that will be in the right temperature zone for a few million years only. OTOH, a few million years CAN be kind of a long time...

greenone
2005-Mar-29, 07:49 PM
this makes me wonder about the galilean satelites, maybe it's high time to buy property on europa...

antoniseb
2005-Mar-29, 08:02 PM
Originally posted by greenone@Mar 29 2005, 07:49 PM
this makes me wonder about the galilean satelites, maybe it's high time to buy property on europa...
It will take 5 billion years for that investment to "pay off". You might be able to put your money into a higher yielding government bond or something. Also, if you DO invest in realestate on Europa, be sure to keep the deed in a very safe place, and make sufe it is written on a very stable material. It might not age gracefully.

Planetwatcher
2005-Mar-29, 09:11 PM
The relatively small region around the star which is just at the right temperature to support liquid water will extend as the red giant expands. This means that previously frozen planets (like Mars) could thaw out and life might have a second chance to happen in a solar system.
But now even though a giant, as a red star it is cooler, so I'm wondering wouldn't the cooliing equal out and cause Earth be safe during the first part of the red giant expansion phase?
At least until the Sun expanded to a point to make life on Earth impossible.
And even then that wouldn't mean Mars would be any safer, because the Sun could expand to make life on Mars impossible as well.


BTW: as I recall reading the book, a few years back, Planet of the Apes was set on a habitable planet around a certain red giant in Orion.
Unless the book was drasticly different then the origional movie, the asteronaunts only thought they had landed on a planet in orbit of Betlegiuse, (a red giant and the brightest star in Orion) However, the ship had actually turned around and returned to Earth. An Earth 2,000 years from now which was ruled by apes.

wstevenbrown
2005-Mar-29, 10:26 PM
I also question whether the red-giant phase would be stable enough and long-lasting enough for life to develop there from scratch. On the bright side, the habitable zone for very luminous stars is wider, if you don't mind the spectral range. The likelihood is that perhaps three times as much usable real estate is available to migrant, developed species-- for a few million years, that is. We would have to learn some new meteorology, tho. Weather patterns are bound to be a bit different when the sun takes up 30 to 50 degrees of sky. Shorter nights mean highly PO'd astronomers! ;) Steve

John L
2005-Mar-29, 10:34 PM
I think that the duration of the red giant phase will vary from star to star and according to the article can be up to a billion years. That was enough time for life to start on Earth, but only single celled life.

My issue is the surface instability of a red giant. In that phase the star will begin to shed surface material. It won't be the final blow off of the out envelope to expose the white dwarf core, but things like solar flares and coronal mass ejections would be many times more powerful and more frequent. That can't be a good place to live on a world like Mars with no protective magnetic field.

Greg
2005-Mar-30, 04:37 AM
In the sun's red giany phase it is very likely that Earth will be a roasted cinder within the sun's outer layers if it isn't completely dissociated before that.
As far as extra-terrestrial life is concerned, the good news is that such old systems are likely to be devoid of mass extinction inducing asteroid or comet collisions. The bad news is that the red giant phase would probably not be long enough for complex life forms to evolve. Still this is a very good topic for debate and discussion. Certainly such systems are very likely to have habitable bodies by our standards that we could terraform until they refreeze when the star becomes a white dwarf.

jsheff
2005-Mar-30, 02:38 PM
Those numbers strike me as highly suspicious. Red giant stars, though extremely luminous, are relatively rare. According to the American Association of Variable Star Observers, which quotes the latest Hipparchos data, the nearest red giant star, Gamma Crucis, is 88 light-years away. I can't find a figure for how many there are within 100 light-years, but assuming the number of any type of star in a given volume goes up as the cube of the distance, there should be roughly (100/88)*(100/88)*(100/88) = only about 1.5 red giants within 100 light-years. A difference of a factor of 66! What gives?

antoniseb
2005-Mar-30, 03:14 PM
Originally posted by jsheff@Mar 30 2005, 02:38 PM
I can't find a figure for how many there are within 100 light-years, but assuming the number of any type of star in a given volume goes up as the cube of the distance, there should be roughly (100/88)*(100/88)*(100/88) = only about 1.5 red giants within 100 light-years.
Red Giant is a relatively brief phase that most stars go through. If the sun lasts 10 billion years, and is a red giant for ten million years, then only one sun-like star in a thousand should be in the red giant phase now... and THAT assumes that there has been a continuous creation process of stars for over ten billion years. The Milky Way's baby-boom of new stars started eight billion years ago, which should make red giants even more rare.

Mr. Smartypants gamer guys
2005-Mar-30, 04:28 PM
hey guys out of all posibiltity isnt it realavent that the sun will grow so big it will engulf mars to? :unsure:

John L
2005-Mar-30, 04:29 PM
The overall point is that when searching for worlds that are or could be made habitable you shouldn't discount the red giants. Although in the grand scheme of things the life of a habitable world will be breif, on a human time scale it would be long enough to form a civilization.

Mr. Smartypants gamer guy
2005-Mar-30, 04:42 PM
oh ya b4 i forget is there any chance the solar system would be sucked up by the supermassive blk hole at the center of our galaxy b4 the sun expands and blows up? :( :blink: :unsure:

Erimus
2005-Mar-30, 04:45 PM
I think they're using a broader definition of red giant; if we want to include orange stars like Arcturus as "red" giants, then that bad boy is only 37 light-years away. Same deal with stars like Pollux, Aldebaran, etc.

For the record, astronomers have been talking about the possibilities of the post-main sequence Solar System for a long time. I remember reading an article years ago about the possibilities of a warm and wet Titan during the Sun's red giant phase, especially if life brought there by Huygens was able to survive dormant that long (!); the probe was not stringently sterilized, by the way.

I personally wouldn't look at post-main sequence systems for developed or advanced life, but for finding beginning life I think it would be a great idea to look. I'm interested in exolife wherever it turns up, regardless of whether its destined to survive for a million years or a billion.

I wouldn't mind colonizing red giant system, either; if the system will be stable for say, 100 million years, then that's millions of times longer than human civilization has existed on Earth, and more than enough time to be fruitful and multiply, then relocate when the going gets tough. A red giant star might even have some advantages over a MS one; less UV radiation, a (probably) quieter EM environment, etc. However, any serious variability could be a disaster (and many late-type stars are variable in one way or another); if the Sun irregularly varied by say, 5% in brightness, we'd definitely feel it on Earth.

lswinford
2005-Mar-30, 08:13 PM
Looking out our own historical distribution of humanity, then projecting some future plausible interstellar mass-transit capacity, we could waft through such comparatively temporate comfort zones with ease. Humanity is a remarkably mobile lot. As for home-grown life during the comparatively brief window of opportunity a red giant might bring, hmm, I doubt we would find much.

Oh, and for Planetwatcher, there were some good differences between the book and the movies. I would have loved to see the stock market--they had three dimensional trading zones with apes swinging to get an advantage to make a quick trade. My girlfriend at the time thought she would have enjoyed seeing Heston naked--in the book humans were not permitted clothes and in the initial period of the landing, the native humans stole the astronaut's clothing, a sign of those other primate oppressors. It was a fun yarn from which Hollywood took reasonable license.

Spacemad
2005-Mar-30, 08:33 PM
Originally posted by Mr. Smartypants gamer guy@Mar 30 2005, 04:42 PM
oh ya b4 i forget is there any chance the solar system would be sucked up by the supermassive blk hole at the center of our galaxy b4 the sun expands and blows up? :( :blink: :unsure:

I don't think there's any danger of that happening - our sun would have long ago ceased to be anything more than a white dwarf at most - if not an even colder cinder!

I don't think the black hole at the centre of the Milky Way will have enough time to grow that big & swallow up whatever remnants may remain in this vicinity!!!

lswinford
2005-Apr-07, 09:05 PM
Considering the apparent equilibrium the waves (arms) of stars in spiral about our core, and the very persistence of the core, the black hole or holes at the center would have to really step up their progress in order to suck us down before our maturing star expires. We would be sucked up by the local gravity monster ourselves except that we have enough angular momentum to balance the combined expansive (solar wind) and attractive (gravity) forces (magnetism might have a role as well, as in perhaps we orbit in conjunction with a magnetic line of force from the sun). All said, we are in a place of relative equilibrium. The stars of our galaxy, across the great distances and carrying their own mass' momentum are in a relative equilibrium. In time, however, there is a propensity to wind down and those massive objects in the center gobbling up star masses have a propensity to additional drawing power as the balances slowly change. I expect we have more likelihood of doing our nova thing to contribute to future star generations long before the galaxy's central masses have pulled us in. --for what its worth. :(

Mr. Smartypants gamer guy
2005-Apr-13, 04:14 AM
k if ur so sure spacemad can you show me a picture and the curent stats on it cause it would be kinda weired if we get sucked up like that b4 our sun blows up... <_< :unsure: >_>

Spacemad
2005-Apr-14, 08:38 PM
Originally posted by Mr. Smartypants gamer guy@Apr 13 2005, 04:14 AM
k if ur so sure spacemad can you show me a picture and the curent stats on it cause it would be kinda weired if we get sucked up like that b4 our sun blows up... <_< :unsure: >_>

There&#39;s no danger of being "sucked up" by the black hole at the centre of the Milky Way. it&#39;d take more millions of years than our sun will ever last&#33;

Mr. Smartypants gamer guy
2005-Apr-15, 04:04 PM
i still want proof cause i plan on saving the human race from that crap and i want to see data... so if there is none then... well lets try and say there could be a tiny posibility

Nick4
2005-Apr-24, 03:07 AM
This is a good thought but if it did make life on a frozen planet like mars life wouldnt last very long. The star would finish up the last bit of fual it had and go nova or super nova wiping out all life in the solor system. But life dosent stop their completly, once the star has exploded and made its nebula it will form more stars and maby planets that life could again exist.