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160 Billion! The New Estimate of Alien Planets in the Milky Way

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The Kepler Space Mission's search for habitable planets in a tiny window representing 1/400th of the Milky is proving Arthur C Clark, author of Space Odyssey 2001 right:  "The idea that we are the only intelligent creatures in a cosmos of a hundred billion galaxies is so preposterous that there are very few astronomers today who would take it seriously," Clarke wrote. " It is safest to assume therefore, that they are out there and to consider the manner in which this may impinge upon human society."

According to a fascinating new study a new study based on Kepler data on the average, each of the 100 billion or so stars in our galaxy hosts at least 1.6 planets, bringing the number of likely exo worlds to more than 160 billion. Recent research conclude that large numbers of these exoplanets are likely to be small, rocky Earth-like low-mass planets, which  appear to be much more abundant than large ones.

"This statistical study tells us that planets around stars are the rule, rather than the exception," said study lead author Arnaud Cassan of the Paris Institute of Astrophysics. "From now on, we should see our galaxy populated not only with billions of bright stars, but imagine them surrounded by as many hidden extrasolar worlds."

To date, astronomers have discovered more than 700 planets beyond our own solar system, with 2,300 additional candidates found by NASA's Kepler space telescope awaiting confirmation.

In the new study, the researchers looked at data gathered by a variety of Earth-based telescopes, which scanned millions of stars from 2002 to 2007 for microlensing events, then closely analyzed about 40 of these events and discovered that three betrayed the presence of an alien planet around a star. One of these planets is a bit more massive than Jupiter, one is comparable to Neptune and the third is a so-called "super-Earth" with a mass about five times that of our home planet --an impressive yield considering how perfectly aligned multiple bodies must be to yield an explanet detection via microlensing.

Further, according to the researchers' calculations, every planet in the Milky Way harbors an average of 1.6 planets in the 0.5-10 AU range, which in our solar system corresponds roughly to the swath of space between Venus and Saturn.

Since astronomers estimate that our galaxy contains about 100 billion stars, that works out to at least 160 billion alien planets. Cassan and his team report their results in the Jan. 12 issue of the journal Nature. The true number of alien worlds may be quite a bit larger than 160 billion. Some planets hug their host stars more closely than 0.5 AU, after all, and others are more far-flung than 10 AU. And a great many likely have no host star at all.

"We used to think that the Earth might be unique in our galaxy," study co-author Daniel Kubas, also of the Paris Institute of Astrophysics, said in a statement. "But now it seems that there are literally billions of planets with masses similar to Earth orbiting stars in the Milky Way."

The Daily Galaxy via Kepler Missionspace.com and centauridreams.org.

Comments

Derr!

Kind of puts our squablings over land, here on Earth, into perspective.....

Our galaxy has over 400 billion stars according to some estimates. If that is the case 160 billion planets is a very low estimate. If we are an average solar system with 8 planets than you can multiply 400 billion times 8 and it's still probably low.Some stars may have ten times as many as our sun does.

Hollow wood

The Kepler Space Mission's search for habitable planets in a tiny representing 1/400th of the Milky is proving Arthur C Clark, author of Space Odyssey 2001 right: "The idea that we are the only intelligent creatures in a cosmos of a hundred billion galaxies is so preposterous that there are very few astronomers today who would take it seriously," Clarke wrote.
To date, astronomers have discovered more than 700 planets beyond our own solar system, with 2,300 additional candidates found by NASA's Kepler space telescope awaiting confirmation.

And why was I thrown exact on this cracy planet?

Could these planets(potentially 400 billion x 8 according to Marion) make up the missing matter that has science looking for "dark" matter or does the missing mass add up to much more than that?

Sorry I should also have said, when replicated across the Universe.

Simon
If that was the case I am sure the headline would of been "Dark Matter Mystery Solved!" BUT every drop helps I am sure.

That = 222.2 planets per person on Earth. Take your pick!

Thanks smartypants but even so, multiply billions of galaxies across the Universe by Marion's estimated 3200 billion planets (and assuming they're a mix of gas giants and rocky mars type planets) must add up to quite a few "drops" of matter that we never knew was there before don't you think?

Even Kepler might demur that NASA's search telescope should be named the Bruno after Giordano, who was executed in 1600 for saying there are an "infinite number of habitable worlds." NASA's budget has been spent to prove Bruno right. Bruno said an infinite number, and 160 billion for our own mediocre-sized galaxy is a good start on infinity. Of course, the proportion that are habitable is turning out to be low, but not infinitesimal. See my Worlds of Giordano Bruno (Cortex Design, UK).

@ habitableworld

Except infinity is not a number, it is the human concept of no limit. How would you go about proving infinity exists?

Simon
No doubt thats a lot of gas and dirt. Honestly I have no idea of its weight. Still with dark matter being the news worthy and cash for speeches item that it is, for the article to not even mention the possibility, I assume the answer is still no. But I am sure you know how assume breaks down so even an evil super scientist like me may be wrong. I do remember reading a while back that some scientist were thinking that brown dwarfs and small black holes might be part of dark matter, so with that I agree these planets will add in to the equation.

Maybe all the dark matter is just parallel universes unseen and undetectable except for gravitational forces. They are all around us and we don't know it.

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