New kind of planet discovered
May 18th, 2011
01:00 PM ET

New kind of planet discovered

The planets in our solar system get along with each other pretty well. But sometimes when multiple planets orbit the same star, there’s a confrontation that is, the gravity of one planet interferes with another’s. In this way, smaller ones can get kicked out, left to float in the dark without a star to go around.

These “lonely planets” represent an entirely new category of planets, and are perhaps more numerous in our galaxy than stars, scientists report Wednesday in the journal Nature.

"It gives us a good clue about how planet formation works. It suggests that there's a lot of violent encounters between planets near the end of the planet formation process," said David Bennett, astronomer at the University of Notre Dame.

Bennett and colleagues discovered 10 such planets, each probably the size of Jupiter, in a survey called the Microlensing Observations in Astrophysics, which used a 5.9-foot telescope in New Zealand to scan our galaxy, the Milky Way.

These planets are likely gaseous, and would not be hospitable to life.

Here’s how they may have formed: Generally speaking, a planet is born when a gas cloud around a star collapses into a disc shape. There are a few different theories about what happens next, but the leading idea is that the dust and the ice begin to stick together, growing into larger objects because of gravitational attraction, Bennett said. When those giant objects become about 10 times the mass of the Earth, they begin to pull in large amounts of hydrogen and helium gas, resulting in Jupiter-sized planets about 300 times the mass of the Earth, he said.

Astronomers haven’t seen these planets with a naked eye, but have detected them indirectly. When a planet passes in front of a distant star, that star brightens. That’s because the planet’s gravity warps the light from the star, as if magnifying it. This is called “gravitational microlensing.” Albert Einstein correctly predicted this effect in 1936.

Scientists can estimate the mass of a planet by looking at how long this brightening event lasts. For Jupiter-sized planets, it happens over the course of one or two days, which is what they observed in this study.

Previous explorations of distant planets found evidence of free planets also, but didn’t have a good estimate of how many there were or how big, said Takahiro Sumi, associate professor at Osaka University’s Department of Earth and Space Science and the lead author of the study.

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Filed under: Science • Space
soundoff (140 Responses)
  1. Joey

    HISTORIC breakthrough in medicine!
    Tell me, tony: how did Islam cause HIV?
    Did Mary Baker Eddy speak to that?

    May 18, 2011 at 9:10 pm | Report abuse |
  2. Joey

    If I think very, very intensely, and really focus, can I psychically will a virus into existence?

    May 18, 2011 at 9:14 pm | Report abuse |
  3. stewie

    No, but if some people did it could cause a brain fart. Just saying.

    May 18, 2011 at 9:58 pm | Report abuse |
  4. stewie

    Tony, I would suggest that you read up on the history of Al-Andalus, after the moors took control of Spain it ushered in an era of peace and enlightenment among Jews,Christians and Muslims. In fact Christians and Jews held favored status over muslims . Mathematics, the arts and science all flourished under moorish rule. Yes there has been a major rift since then but some of that can be blamed on the Crusades.

    May 18, 2011 at 10:27 pm | Report abuse |
    • ishiibrad

      I thought they were called the Mops? (ask the bubble boy )

      May 19, 2011 at 12:07 am | Report abuse |
  5. Bill Wood

    Maybe these lonely planets and other stuff floating out there) could make up a chuck of that "dark matter" for which we have yet to be able to account.

    May 19, 2011 at 2:07 am | Report abuse |
    • Al

      I was wondering the same thing. Was disappointed that it wasn't addressed in this article.

      May 20, 2011 at 7:49 am | Report abuse |
    • Dani3l

      I thought of that as well. Planets adrift and not bound to a stellar orbit could certainly comprise a fair amount of mass, especially if more numerous (though obviously less massive) than stars. If not mentioned in this article, I imagine that scientists are still looking at how reasonably viable such an hypothesis is.

      May 26, 2011 at 6:08 pm | Report abuse |
  6. jim

    Once again. Gene Roddenberry has been proven right after being scoffed at.

    May 19, 2011 at 7:22 pm | Report abuse |
  7. jim

    Once again Gene Roddenberry has been proven right after being scoffed at.

    May 19, 2011 at 7:22 pm | Report abuse |
  8. Leonard

    hahaha funny planet

    May 23, 2011 at 1:16 pm | Report abuse |
  9. Leonard

    this pic makes me hard

    May 23, 2011 at 1:16 pm | Report abuse |
  10. David

    Einstein predicted gravitational lensing n 1916, not 1936. Typo.

    June 8, 2011 at 1:47 pm | Report abuse |
  11. Kramer2605

    "That's no moon, it's a space station!"

    July 26, 2011 at 2:34 pm | Report abuse |
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