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View Full Version : How Common are Solar Systems Like Ours?



Fraser
2010-Jan-05, 09:20 PM
Solar system montage. Credit: NASAOn the whole, we'd like to think we're special, but we also hope we aren't alone in the Universe. Astronomers have been trying to figure out just how common solar systems like ours are across the cosmos, and during one moment of epiphany one scientist figured out how to make the [...]

More... (http://www.universetoday.com/2010/01/05/how-common-are-solar-systems-like-ours/)

Buttercup
2010-Jan-05, 09:38 PM
Probably uncommon, considering what "systems" we have spied out there usually consist of a debris belt and a "Super Jupiter" or "Super Earth" ... which usually orbit very closely to their host star (far too hot) or waaaay out (far too cold) to host life. :(

Probably our Solar System is a bit on the unique side. And I don't think that's bias. ;)

01101001
2010-Jan-06, 12:58 AM
Probably uncommon, considering what "systems" we have spied out there usually consist of a debris belt and a "Super Jupiter" or "Super Earth" ... which usually orbit very closely to their host star (far too hot) or waaaay out (far too cold) to host life.

We haven't looked at a lot of systems and then determined that's the usual arrangement. We have looked at systems that show themselves to our methods, and those usual arrangements make them detectable.

We see what we are able to see.

Wikipedia: Extrasolar planets :: Number of stars with planets (http://en.wikipedia.org/wiki/Extrasolar_planet#Number_of_stars_with_planets):


Planet-search programs have discovered planets orbiting a substantial fraction of the stars they have looked at. However, the total fraction of stars with planets is uncertain because of observational selection effects. The radial-velocity method and the transit method (which between them are responsible for the vast majority of detections) are most sensitive to large planets on small orbits. For that reason, many known exoplanets are "hot Jupiters": planets of roughly Jupiter-like mass on very small orbits with periods of only a few days.

George
2010-Jan-06, 08:11 PM
We haven't looked at a lot of systems and then determined that's the usual arrangement. We have looked at systems that show themselves to our methods, and those usual arrangements make them detectable. I am a little surprised that they didn't put a little more speculative tone to their estimatation or a little more effort in applying the other methods used to extrapolate to their conclusion. The microlensing method they mentioned has only found planets within 9 star systems. These planets are close to the size of Jupiter with none being close to the mass of Earth, though a few are closer to Earth's mass than Jupiter's.

I'm pleased to see their estimate and am sure its worthy of note, but it just seems a bit overstated or a little premature given all the newer, higher resolution studies that are beginning to take effect. Show me masses at 0.001 Jupiters, then I'll more receptive.

Am I too Earthopomorphic? :)

Swift
2010-Jan-06, 08:58 PM
Probably our Solar System is a bit on the unique side. And I don't think that's bias. ;)
As binary man said, there is a bias, but it is not of the kind you were winking about. Because of our detection methods, there is a bias to finding big planets close to their star. As our detection methods have improved, the relative percent of "hot Jupiters" has fallen, but I still don't believe we have the technology to find systems like ours, even if they were only 10s of lightyears away.

George
2010-Jan-06, 10:44 PM
As binary man said, there is a bias, but it is not of the kind you were winking about. Because of our detection methods, there is a bias to finding big planets close to their star. As our detection methods have improved, the relative percent of "hot Jupiters" has fallen, but I still don't believe we have the technology to find systems like ours, even if they were only 10s of lightyears away.

If my math is right, and it's rushed at the moment, a Venus-sized planet would be visible to even the HST if it were orbiting a Solar twin no further than about 80 lyrs. The problem, of course, is all that glare, but I've been amazed at what astronomers have accomplished in beating back this problem. [Getting surface features would be quite a trick when this disk would only have about 2.5 microseconds of arc. :)]

Buttercup
2010-Jan-06, 10:51 PM
I wonder how common planets like Saturn are: With those many-banded majestic rings. :D Probably pretty rare. Maybe Saturn is unique in the entire universe!

I like to think so. :)

George
2010-Jan-07, 01:41 AM
I wonder how common planets like Saturn are: With those many-banded majestic rings. :D Probably pretty rare. Maybe Saturn is unique in the entire universe!

I like to think so. :)
Although Jupiter, Neptune, and Uranus have rings, it is hard to imagine an exoplanet with greater majestic rings than Saturn.

A.DIM
2010-Jan-08, 02:00 PM
Hmmm... the UT story gives the average for systems like ours in the universe while other sources I've read state the average is for our galaxy.

From UT:

... they concluded that about 10 – 15 percent of stars in the universe host systems of planets like our own, with several gas giant planets in the outer part of the solar system. "Now we know our place in the universe," said Ohio State University astronomer Scott Gaudi. "Solar systems like our own are not rare, but we're not in the majority, either."


From AstroBio:

"They’ve concluded that about 15 percent of stars in our galaxy host systems of planets like our own, with several gas giant planets in the outer part of the solar system. “Now we know our place in the universe,” said Ohio State University astronomer Scott Gaudi. “Solar systems like our own are not rare, but we’re not in the majority, either.”






And whether 10 or 15 percent I come up with billions of systems like ours, in the MW alone. And Gaudi thinks this is enough to "know our place in the universe?"
Bah!
We barely even know our nearest neighbors!

A.DIM
2010-Jan-08, 02:21 PM
Science Daily has it as "In All the Universe .... " while PhysOrg has it as "In all the galaxy...."

:think:

I wonder which ...