News / Science & Technology

Milky Way Could Contain 100 Billion Planets

A section of the Milky Way as seen by the Kepler telescope.
A section of the Milky Way as seen by the Kepler telescope.
It seems like hardly a week goes by without another planet being discovered in some far off stellar system, but a new study, released by the California Institute of Technology, indicates there will likely be many, many more such discoveries.

The Caltech team made this conclusion based on analyzing the planets orbiting the Kepler-32 star, which contains five planets and which the scientists say is representative of the vast majority of stars in our galaxy. Kepler-32 is classified as an M dwarf, and scientists say three out of every four stars in the galaxy are M dwarfs, also known as red dwarfs.

"There's at least 100 billion planets in the galaxy—just our galaxy," says John Johnson, assistant professor of planetary astronomy at Caltech and coauthor of the study, which was recently accepted for publication in the Astrophysical Journal. "That's mind-boggling."

Scientists say their estimate of 100 billion planets is conservative because it doesn’t take into account planets which may be orbiting further away from M dwarfs or planets orbiting other types of stars.

According to the scientists, Kepler-32’s five planets, which were detected by the Kepler space telescope, are similar in size to Earth. They are also similar to other planets discovered around other M dwarf stars. They all orbit very close to their star, no further than one-third the distance Mercury orbits our Sun. This is typical of M dwarf systems, Johnson said.

While the planets may resemble Earth in size, the Kepler-32 system differs from the Solar System. The star is much cooler than the sun, has only five percent of its brightness and is only half the size.

Johnson said an alternate headline for the discovery is just how much of a “weirdo” our own solar system is compared to the vast majority of systems in the galaxy.

Still, the Kepler-32 star system does have what is called a “habitable zone,” where liquid water could exist. In the Kepler-32 system, only the outermost planet is in that zone,  but Johnson said it likely resembles Neptune and would likely not support life.

Because of its orientation, Kepler-32 presents itself as a great opportunity to study as all the planets’ orbits are in a plane and can be viewed edge-on as they briefly block the light from the star. These small changes in light allow scientists to determine the planets’ characteristics such as size and orbital speed.

"I usually try not to call things 'Rosetta stones,' but this is as close to a Rosetta stone as anything I've seen," Johnson says. "It's like unlocking a language that we're trying to understand—the language of planet formation."

Johnson said the next big question would be if any of the planets in the habitable zones around M dwarf stars could support life.

“There are 20 different factors on Earth, and we don’t know how to rank them,” Johnson said. “Do we need a moon? It’s important. How critical? Do you have to have plate tectonics?”

Johnson said those questions are best suited for climate scientists and geologists.

“Until we have the ability to study those things, we won’t know if they’re hospitable,” he said. “If you were looking at our Solar System from an alien world, you might write a press release saying you’d discovered two planets in the habitable zone. Venus is in the habitable zone, but it’s not a good vacation spot.”

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Comment Sorting
by: Ciaran Mulcahy. from: Dublin, Ireland.
January 07, 2013 6:50 AM
Unless one believes in a religious explanation for life, and its creation; or, even, that human existance is so rare, that the fact that what we regard as human life, developed at all, is miraculous; we 'have' to be able to prove that our planet is 'not' the only place where human-life exists.

Does recent information sent back from electronic equipment on Mars, aid us to one day believe, that human-life on this planet, 'could' have moved to Earth, from Mars?.

Something like two, or three decades ago, scientists and astronomers believed, at least for a while, that radio-telescopes had detected the reception of a decipherable alphabetical letter-symbol, which they believed, could have been real, and extra-terrestrial in origin. What part of the universe, and its galaxies, was it detected as possibly originating from; and in what Broadcast-Frequency Range?. Could the 'apparent' transmission of an 'apparent' random alphabetical-letter, been due to a random burst, from a known, or, equally, unknown gas, or liquid, from some undetermined source?

by: sifandy from: Indonesia
January 06, 2013 9:47 AM
wow amazing, that very wonderfull

by: ReadIt from: Miami
January 06, 2013 12:15 AM
The Universe is a fractal, organic system, which reproduces complementary, social networks of energy and information that self-organize themselves in bigger, self-similar scales which constantly undergo endless cycles of creation and destruction. All entities are 'cellular societies' organized through energy and information networks that bring about processes of social evolution of parts into wholes. All sciences share the laws of duality, systems and organicism since the properties of energy and information remain invariant in all the scales of reality. The result is the fractal structure of the Universe, a superorganism made of smaller superorganisms. :-)

by: James from: Nebraska
January 04, 2013 9:03 PM
Gazing is the point. One will learn where it all comes from by studying evidence, not mysticism.

And shadows on the wall? No. They are looking at actual star systems that can be demonstrated to exist.

by: Rob Swift from: Great Britain
January 04, 2013 6:21 PM
One day these people will get clued up. They marvel at the material universe without grasping the overall picture. They gaze at stars like they are gazing at a screen, without grasping how, or from where, it is all projected . They marvel at mere shadows on the wall.

by: Dan from: Utah
January 04, 2013 4:57 PM
So many possibilities, so little time, and the question of the century… with so many planets in the universe, what is the possibility of “intelligent” life on one of them? Let’s not fool around and assume this intelligent life will be about where humans are or at least close to it. Let’s imagine there is one out there that has been around for hundreds of millions of years. This is an intelligent species that has learned not to destroy itself because it still exists… with all that knowledge, surely they would know how to do a good job of it if they were so inclined. Therefore, we have a species that is at least at peace with itself and most likely others. We are talking about hundreds of millions of years beyond where we are today in knowledge and wisdom. Hmmm, I wonder if we would consider them gods if we were to meet them or perhaps we have. Perhaps that is why we are the dominant species on earth, except for all those pesky bacteria, that is. 

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