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WASHINGTON — The more astronomers look for other worlds, the more they
find that it’s a crowded and crazy cosmos. They think planets easily
outnumber stars in our galaxy and they’re even finding them in the
strangest of places.

And they’ve only begun to count.



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( Zdenek Bardon/ProjectSoft, European Souther Observatory / Associated
Press ) - This 2011 handout photo provided by the European Southern
Observatory, shows the Milky Way above the La Silla Observatory in
Chile. The more distant telescope in the photo was used to survey
planets in our galaxy using a time consuming technique. The results
indicate that on average there are 1.6 larger planets per star in our
solar system, but that’s mostly looking at planets that are far from
their star. Other methods look more on close-in planets and putting
those techniques together, astronomers think that means stars in the
Milky Way probably average well over two planets.




. 

Three studies released Wednesday, in the journal Nature and at the
American Astronomical Society’s conference in Austin, Texas,
demonstrate an extrasolar real estate boom. One study shows that in
our Milky Way, most stars have planets. And since there are a lot of
stars in our galaxy — about 100 billion — that means a lot of planets.

 “We’re finding an exciting potpourri of things we didn’t even think
could exist,” said Harvard University astronomer Lisa Kaltenegger,
including planets that mirror “Star Wars” Luke Skywalker’s home planet
with twin suns and a mini-star system with a dwarf sun and shrunken
planets.

 “We’re awash in planets where 17 years ago we weren’t even sure there
were planets” outside our solar system, said Kaltenegger, who wasn’t
involved in the new research.

Astronomers are finding other worlds using three different techniques
and peering through telescopes in space and on the ground.

Confirmed planets outside our solar system — called exoplanets — now
number well over 700, still-to-be-confirmed ones are in the thousands.

NASA’s new Kepler planet-hunting telescope in space is discovering
exoplanets that are in a zone friendly to life and detecting planets
as small as Earth or even tinier. That’s moving the field of looking
for some kind of life outside Earth from science fiction toward just
plain science.

One study in Nature this week figures that the Milky Way averages at
least 1.6 large planets per star. And that is likely a dramatic
underestimate.

That study is based on only one intricate and time-consuming method of
planet hunting that uses several South American, African and
Australian telescopes. Astronomers look for increases in brightness of
distant stars that indicate planets between Earth and that pulsating
star. That technique usually finds only bigger planets and is good at
finding those further away from their stars, sort of like our Saturn
or Uranus.

Kepler and a different ground-based telescope technique are finding
planets closer to their stars. Putting those methods together, the
number of worlds in our galaxy is probably much closer to two or more
planets per star, said the Nature study author Arnaud Cassan of the
Astrophysical Institute in Paris.

Dan Werthimer, chief scientist at the University of California
Berkeley’s search for extraterrestrial intelligence program and who
wasn’t part of the studies, was thrilled: “It’s great to know that
there are planets out there that we can point our telescopes at.”

Kepler also found three rocky planets — tinier than Earth — that are
circling a dwarf star that itself is only a bit bigger than Jupiter.
They are so close to their small star that they are too hot for life.

 “It’s like you took your shrink ray gun and you set it to seven times
smaller and zap the planetary system,” said California Institute of
Technology astronomer John Johnson, co-author of the study presented
Wednesday at the astronomy conference.

Because it is so hard to see these size planets, they must be pretty
plentiful, Johnson said. “It’s kind of like cockroaches. If you see
one, then there are dozens hiding.”

It’s not just the number or size of planets, but where they are found.
Scientists once thought systems with two stars were just too chaotic
to have planets nearby. But so far, astronomers have found three
different systems where planets have two suns, something that a few
years ago seemed like purely “Star Wars” movie magic.

 “Nature must like to form planets because it’s forming them in places
that are kind of difficult to do,” said San Diego State University
astronomy professor William Welsh, who wrote a study about planets
with two stars that’s also published in the journal Nature.

The gravity of two stars makes the area near them unstable, Welsh
said. So astronomers thought that if a planet formed in that area, it
would be torn apart.

Late last year, Kepler telescope found one system with two stars. It
was considered a freak. Then Welsh used Kepler to find two more. Now
Welsh figures such planetary systems, while not common, are not rare
either.

 “It just feels like it’s inevitable that Kepler is going to come up
with a habitable Earth-sized planet in the next couple of years,”
Caltech’s Johnson said.

___

Online:

Nature: http://www.nature.com/nature

American Astronomical Society: http://www.aas.org

http://www.washingtonpost.com/politics/crowded-cosmos-in-milky-way-planets-more-plentiful-than-stars-even-in-unexpected-places/2012/01/11/gIQAf5EDrP_story.html?tid=pm_politics_pop


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