2 billion earthlike planets in the milky way .. maybe

[Molinaro]

Preliminary analysis of the data from the Kepler telescope indicate that there could be as many as 2,000,000,000 earthlike planets in the Milky Way. Those would be planets 0.8 to 2.0 times the size of earth, orbiting a sunlike star within the habitable zone.

http://www.space.com/11188-alien-earths-planets-sun-stars.html

This telescope is identifying a lot of targets for the next generation of space based telescopes.

 

[Corsair 115]

Preliminary analysis of the data from the Kepler telescope indicate that there could be as many as 2,000,000,000 earthlike planets in the Milky Way.

What does "Earth-like" mean in this context? From a skimming of the article, it appears to refer only to planets with a mass somewhat similar to Earth's. Having a similar mass is but one of the many things one would need to have in common for a planet to be truly called "Earth-like." Venus has a mass about 82% that of the Earth's but I don't think many folks would call Venus "Earth-like."

It seems more accurate to say "as many as two billion terrestrial planets."

 

[wollery]

What does "Earth-like" mean in this context? From a skimming of the article, it appears to refer only to planets with a mass somewhat similar to Earth's. Having a similar mass is but one of the many things one would need to have in common for a planet to be truly called "Earth-like." Venus has a mass about 82% that of the Earth's but I don't think many folks would call Venus "Earth-like."

It seems more accurate to say "as many as two billion terrestrial planets."

To an astronomer "Earth-like" means similar in mass to the Earth and rocky, and that's about it. Some people also use it to mean "in the habitable zone", but they usually specify that in talks or papers. The atmosphere is not considered in such general statements.

This study also doesn't include non-solar type stars, which could also harbour Earth-like planets capable of supporting life, so it could actually be an underestimate of the number of possible life bearing planets. It's only "Earth analogues" that they're considering.

 

[Cuddles]

This study also doesn't include non-solar type stars, which could also harbour Earth-like planets capable of supporting life, so it could actually be an underestimate of the number of possible life bearing planets. It's only "Earth analogues" that they're considering.

It also misses out moons, and given the number of gas giants out there there are likely to be a whole bunch of Europas and Titans around as well.

 

[RossFW]

I guess the elephant in the room is how this might effect the chances of extra-terrestrial life existing. Plug these numbers into the Drake equation, and it seems much more likely.

Still, seeing as the one solar system we know about has four bodies that come close to life-supporting conditions (MArs, Venus, Europa and Titan (and Europa JUST might actually HAVE life)) a field of 2,000,000,000 chances SHOULD at least yield some exo-plankton!!

 

[Chucky]

It also misses out moons, and given the number of gas giants out there there are likely to be a whole bunch of Europas and Titans around as well.

And I believe from early reports I've heard that it's almost more likely that gas giants are in closer orbits to their suns in many systems than they are in ours. I'm sure many of those will fall into the Goldilocks zone.

 

[MG1962]

And I believe from early reports I've heard that it's almost more likely that gas giants are in closer orbits to their suns in many systems than they are in ours. I'm sure many of those will fall into the Goldilocks zone.

I was only thinking about that the other day. Rather than target Earth like planets. Look at these giants and their moons

 

[Cuddles]

And I believe from early reports I've heard that it's almost more likely that gas giants are in closer orbits to their suns in many systems than they are in ours. I'm sure many of those will fall into the Goldilocks zone.

I haven't really looked into it recently, but I'm not sure that's the case. The problem is that it's much easier to find large planets orbiting close to a star than it is to find anything else. So the fact that we see a lot of them doesn't mean they must be especially common, it just means that we're currently mostly finding the planets that are easiest to find. This will, of course, always be true, but as our technology develops we'll get better at finding smaller and further planets and will come much closer to finding out what the real proportions are.

 

[JoeTheJuggler]

It seems more accurate to say "as many as two billion terrestrial planets."

How on Earth <ahem> is that "more accurate"?

 

[JoeTheJuggler]

I was only thinking about that the other day. Rather than target Earth like planets. Look at these giants and their moons

Drake also suggested twilight zones on tidally locked planets around Red Giants.

But I think we'd do well at this point to find out whatever we can.

I think answering the question, "Are earth-like planets relatively scarce or common?" is a good place to start.

ETA: I would also say money spent on the Kepler Mission is money well-spent!

ETA: And since we only know of one example of life in our own solar system so far, I have no problem with focusing our extrasolar searches on candidates most like that. Before we worry too much about life on extrasolar gas giants or their moons, we should investigate the examples in our own solar system more thoroughly.

 

[MG1962]

Drake also suggested twilight zones on tidally locked planets around Red Giants.

But I think we'd do well at this point to find out whatever we can.

I think answering the question, "Are earth-like planets relatively scarce or common?" is a good place to start.

ETA: I would also say money spent on the Kepler Mission is money well-spent!

Yeah if we get one part of Drakes equation defined it would help a lot

 

[Corsair 115]

How on Earth <ahem> is that "more accurate"?

Because I expect most laypersons would think of "Earth-like" meaning Earth-like, as in similar mass, similar atmospheric composition, etc. I don't think most folks would consider Venus as being "Earth-like" in the general sense.

 

[Dinwar]

Plug these numbers into the Drake equation, and it seems much more likely.

The Drake Equation is useless in terms of predicting probability--there are too many variables which we don't even have good guesses at. It's somewhat useful for wrapping our minds around what questions we need to ask, but I'd say it's limiting effects (eg, we don't look for other criteria because we have THIS equation already) overshadow its benefits.

Also, it's five bodies in our system which "come close to life-supporting conditions"--you forgot to count the Earth (I can understand why, but for statistical purposes you need to include us).

 

[aggle-rithm]

I haven't really looked into it recently, but I'm not sure that's the case. The problem is that it's much easier to find large planets orbiting close to a star than it is to find anything else. So the fact that we see a lot of them doesn't mean they must be especially common, it just means that we're currently mostly finding the planets that are easiest to find. This will, of course, always be true, but as our technology develops we'll get better at finding smaller and further planets and will come much closer to finding out what the real proportions are.

I understand there's a model of solar system development that shows that a star system will tend to sort itself out so that the gas giants are in the outer orbits and small, rocky planets are in the inner orbits. Sort of like the "brazil nut effect" on a much larger scale.

That would mean that the systems with close-in gas giants are probably pretty young.

 

[wollery]

I understand there's a model of solar system development that shows that a star system will tend to sort itself out so that the gas giants are in the outer orbits and small, rocky planets are in the inner orbits. Sort of like the "brazil nut effect" on a much larger scale.

That would mean that the systems with close-in gas giants are probably pretty young.

There are models of solar system development that will show you whatever you want.

The realistic models (i.e. the ones with the most real physics) show that gas giants tend to migrate inwards quite quickly and swallow up everything on the way in. Unfortunately rocky planets seem to take longer to form (in the models), so they get swallowed up too.

The bottom line is that the models don't really work yet, and can't reproduce a Solar system analogue without a bit of fiddling.

 

[Gawdzilla Sama]

So how about "near Earth mass" planets?