Possibile xenobiotic hotspots in our galaxy

[PB666]

http://news.sciencemag.org/space/2015/12/most-likely-spots-life-milky-way

Basically nothing profound, places with a local steelar environment much like our sun has is most likely to support worlds with life on them.

The question is however, do we no what are stellar environment would look like from a telescope 100 light years away?

[Bill Phil]

Yes, we should know. I mean, come on, we have a rendering of the Local Bubble.

[YNM]

Yes, we should know. Voyager, and then there're other experiments (like this one) intended to map the Solar System even in the site of voids. Then, I thought we have, like, Cassini took Earth's spectrum from really far away ?

[PB666]

Im not talking about myopic views of our solar system, most of the earth-like stuff we look at is 100 to 10000 light years away, at this diatance earth is invisible, spectral analysis willl do little good except with the most sophisticated and powerful telescope and only is earth transects the sun during its orbit. 

Im talking about how the cluster of say 100 stars which the sun is in the center of looks like from say 1000 light years away if we say each star occupies a space of 200 cubic light years then 100 stars occupies a volume of 20000 cubic light years Vr = 4/3 pi r ^ 3.   4500 =r^3,  thats roughly 40 ly across from 1000 ly away, how does our group of stars render in someone elses eyes?

[Scotius]

Like 90% of open clusters visible across the sky.

[PB666]

So then how can theybsay there are hotspots for life? 

[Scotius]

It's probably based on the age of the stars, and their distances. To support the life (as we know it :P) you want star system rich in heavier elements, which are produced by stars from earlier generations going supernova. Also stars in young clusters (like Pleiades) tend to be bright and hot - which means they will age faster and become unstable. Density of the cluster is important too - you don't want other stars to be too close to your own system. It would wreak havoc - messing up orbits and scattering comets in unpredictable directions.

[PB666]

Wait, how do we know that there were not closer stars to the sun when it was young?

If a system is too heavy in heavier elements it will go faster to try to burn iron, bad news for a star.

[YNM]

A good site to have life, would most likely have :

- Proper heavy element abundances.

- No other close stars. Even if it were to be a red dwarf.

- Parent star being sun-like. Surprising indeed, but if you consider that most planets of red dwarfs are tidally locked, and most masive stars clumps together, you'll see it as clear as day.

- More than one gas giant. This is half established ; study shows most system are either tiny planetesimals close to parent star or a single hot giant. In solar system, the presence of Saturn and other giants is thought to stop Jupiter from raging itself into a hot giant. On the contrary, lack of giants make planetesimals reluctant to coalesce together.

- Presence of magnetic field on the planet. Look up Mars for the view of otherwise condition.

Additionally, you need 1.4 Sun's mass of inert iron, plus few times a few Suns mass on top of it to cause SN II / SN I B/I C.

 

 

Edited December 10, 2015 by YNM

[kerbiloid]

The star must be stable per at least a billion years. Because any life evolves when generations change each other, not modifying existing bodies. And the a complex lifeform can change only by relatively small portions, as "very much mutated" usually means "very much ill" for it.
So, generations number seems to be limited from below, and the evolution needs at least half of billion years (as on Earth) to evolve from a plankton into nice and beautiful us.
And from zero to infinity to implement the bacteria from scratch.
So, at least a billion years.

This means:
- No giant stars. They live fast, die young.
- No red dwarfs. Because any planet in a habitable zone would be very close to the star and tidally locked. While the red dwarfs are very stable in the sense of lifespan, but very unstable in the sense of radiation. They are based on a convective equilibrium, not a radiation one, and gurgle as a lava lamp once per several months, which means very unstable conditions and very stable radiation blasts.
- No red dwarfs again - because photosynthesis is weak under their light, and until something significant would grow on their planet, the geological activity finishes and circulation of matter stops.

So, it would be a Sun-like star, a yellow dwarf.

The star place would be:

Far from the region with active star formation process.
- Far from the galaxy bulge.
- Far from the galaxy arm front. Preferably in the corotation zone, i.e. at the same orbit radius as Sun has. I.e. where you never cross the arms front because here you revolve around the Galaxy center with the same speed with its arms.
- Far from star clusters. Though the star should appear in a cluster because it needs heavy elemnts to form the planets. I.e. it must leave a star cluster billion(s) years ago.

In a region rich with heavy elements.
- Far from the galaxy outer edge, where only hydrogen is.
- Again, it must leave a star cluster billion(s) years ago.

I.e. the star must situate at the nearly the same orbit as Sun does, between galaxy arms as Sun does. This means just several bubbles of space, each < 1000 l.y. in size, per the whole Galaxy. Inside one of these bubbles we live, while others we can hardly observe because of dust.

So, < 1000 l.y. around the Sun is more or less realistic space to look for life.
A yellow dwarf, far from star clusters, at least a billion years old.

 

The planet would be Earth-sized, as it needs to be enough solid to have a surface, enough large to produce enough much volcanic gases while gravitanional differentiation to create an atmosphere and an ocean. And to keep the atmosphere from dissipation. Mars size is inappropriate.
But not much larger than Earth, otherwise it will be a gas giant.
I.e. 0.5-1.5 Earth masses.

There must be at least one gas giant to clear the space and to stabilize orbits (Jupiter, not Sun, "contains" almost all angular moment of Solar System).
And at least one another gas giant to move the first giant far from the habitable zone. I.e. Jupiter and Saturn.

Very preferably the planet would have an equatorial tilt to make year seasons.
They enforce the evolution speed by testing lifeforms for heat and frost twice per year rather than growing them in an incubator.
But the tilt would not be ~40 degrees and more - otherwise heat and frost would not "come to", but "crash onto".

The planet would rotate enough quickly to prevent the life die from night frost and day heat, but enough slowly to allow more or less continuous chemical reactions. Say, 1 round per 24 Earth hours - not months or minutes.

Very preferably the planet would have a giant moon which:
- Runs tidal waves, splashing lifeforms from water to coast and washing them from coast into water transforming a lifeless rocky coast into a bog with algae and jungles and testing the lifeforms, speeding up their evolution.
- Most probably created that equatorial tilt from the previos point.
- Most probably created that ~24h rotation from the previos point.

The planet must be in a "habitable zone" +- 10%.
A little closer - the ocean will cause greenhouse effect and we get Venus, vice versa - we get an iceball.

Summary:
A yellow dwarf, out of star clusters, < 1000 l.y. from the Sun.
With two gas giants far outside from a habitable zone.
0.5-1.5 Earth mass planet inside the habitable zone, equatorial tilt 15-30 degrees, with a huge moon.

[problemecium]

What about a white dwarf?

For some time now I've had a fan hypothesis that Kerbol is an old white dwarf that's cooled to yellow and at some point lost some of its mass. Perhaps this can be considered in real life, though. A white dwarf could have a similar surface temperature and thus heat output as the Sun (albeit at a closer range) but last as long as a red dwarf, only slowly cooling over billions of years. Even if all life in the system had been wiped out when the white dwarf was formed, if one or more planets managed to cluster in near it afterward, there'd be plenty of time for them to develop life from scratch.
Also, as far as I've been informed, solitary white dwarfs don't do much of anything, meaning little risk of radiation blasts, CMEs, flares, etc.

Edited December 11, 2015 by parameciumkid

[PB666]

7 hours ago, kerbiloid said:

The star must be stable per at least a billion years. Because any life evolves when generations change each other, not modifying existing bodies. And the a complex lifeform can change only by relatively small portions, as "very much mutated" usually means "very much ill" for it.
So, generations number seems to be limited from below, and the evolution needs at least half of billion years (as on Earth) to evolve from a plankton into nice and beautiful us.
And from zero to infinity to implement the bacteria from scratch.
So, at least a billion years.

This means:
- No giant stars. They live fast, die young.
- No red dwarfs. Because any planet in a habitable zone would be very close to the star and tidally locked. While the red dwarfs are very stable in the sense of lifespan, but very unstable in the sense of radiation. They are based on a convective equilibrium, not a radiation one, and gurgle as a lava lamp once per several months, which means very unstable conditions and very stable radiation blasts.
- No red dwarfs again - because photosynthesis is weak under their light, and until something significant would grow on their planet, the geological activity finishes and circulation of matter stops.

So, it would be a Sun-like star, a yellow dwarf.

The star place would be:

Far from the region with active star formation process.
- Far from the galaxy bulge.
- Far from the galaxy arm front. Preferably in the corotation zone, i.e. at the same orbit radius as Sun has. I.e. where you never cross the arms front because here you revolve around the Galaxy center with the same speed with its arms.
- Far from star clusters. Though the star should appear in a cluster because it needs heavy elemnts to form the planets. I.e. it must leave a star cluster billion(s) years ago.

In a region rich with heavy elements.
- Far from the galaxy outer edge, where only hydrogen is.
- Again, it must leave a star cluster billion(s) years ago.

I.e. the star must situate at the nearly the same orbit as Sun does, between galaxy arms as Sun does. This means just several bubbles of space, each < 1000 l.y. in size, per the whole Galaxy. Inside one of these bubbles we live, while others we can hardly observe because of dust.

So, < 1000 l.y. around the Sun is more or less realistic space to look for life.
A yellow dwarf, far from star clusters, at least a billion years old.

 

The planet would be Earth-sized, as it needs to be enough solid to have a surface, enough large to produce enough much volcanic gases while gravitanional differentiation to create an atmosphere and an ocean. And to keep the atmosphere from dissipation. Mars size is inappropriate.
But not much larger than Earth, otherwise it will be a gas giant.
I.e. 0.5-1.5 Earth masses.

There must be at least one gas giant to clear the space and to stabilize orbits (Jupiter, not Sun, "contains" almost all angular moment of Solar System).
And at least one another gas giant to move the first giant far from the habitable zone. I.e. Jupiter and Saturn.

Very preferably the planet would have an equatorial tilt to make year seasons.
They enforce the evolution speed by testing lifeforms for heat and frost twice per year rather than growing them in an incubator.
But the tilt would not be ~40 degrees and more - otherwise heat and frost would not "come to", but "crash onto".

The planet would rotate enough quickly to prevent the life die from night frost and day heat, but enough slowly to allow more or less continuous chemical reactions. Say, 1 round per 24 Earth hours - not months or minutes.

Very preferably the planet would have a giant moon which:
- Runs tidal waves, splashing lifeforms from water to coast and washing them from coast into water transforming a lifeless rocky coast into a bog with algae and jungles and testing the lifeforms, speeding up their evolution.
- Most probably created that equatorial tilt from the previos point.
- Most probably created that ~24h rotation from the previos point.

The planet must be in a "habitable zone" +- 10%.
A little closer - the ocean will cause greenhouse effect and we get Venus, vice versa - we get an iceball.

Summary:
A yellow dwarf, out of star clusters, < 1000 l.y. from the Sun.
With two gas giants far outside from a habitable zone.
0.5-1.5 Earth mass planet inside the habitable zone, equatorial tilt 15-30 degrees, with a huge moon.

This looks like ascertainment bias, we are looking for something like our solar system because this is the system that we understand. there are many stars that will live billions of years longer than our sun. I think the critical issue is to have a star that does not erode the atmosphere even with a dynamo induced magnetic field, if it can get over that hurdle then i think life is possible.  Where u agree with you is that under the circumstances you state above the evoluion of sentient life may be more restricive. There are those that now argue that life existed in the most rudimentary forms on earth within 0.3 billion years of its formation. 

[JetJaguar]

The trouble is, we only know of one planet with life on it, and you can't determine trends from a single data point.  We end up looking for planets that look like Earth because that's all we know.  

Maybe there are astronomers on a red dwarf planet looking back at our Sun and concluding that life is impossible here because any planet in the habitable zone would be so far from it's host star that it would be free to rotate on it's axis and be subject to cycling levels of heat and light.  Therefore, it wouldn't have the steady climate necessary for life.