A Strange Lonely Planet Found without a Star

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An international team of astronomers has discovered an exotic young planet that is not orbiting a star. This free-floating planet, dubbed PSO J318.5-22, is just 80 light-years away from Earth and has a mass only six times that of Jupiter. The planet formed a mere 12 million years ago—a newborn in planet lifetimes.

It was identified from its faint and unique heat signature by the Pan-STARRS 1 (PS1) wide-field survey telescope on Haleakala, Maui. Follow-up observations using other telescopes in Hawaii show that it has properties similar to those of gas-giant planets found orbiting around young stars. And yet PSO J318.5-22 is all by itself, without a host star.

"We have never before seen an object free-floating in space that that looks like this. It has all the characteristics of young planets found around other stars, but it is drifting out there all alone,” explained team leader Dr. Michael Liu of the Institute for Astronomy at the University of Hawaii at Manoa. “I had often wondered if such solitary objects exist, and now we know they do.”

During the past decade, extrasolar planets have been discovered at an incredible pace, with about a thousand found by indirect methods such as wobbling or dimming of their host stars induced by the planet. However, only a handful of planets have been directly imaged, all of which are around young stars (less than 200 million years old). PSO J318.5-22 is one of the lowest-mass free-floating objects known, perhaps the very lowest. But its most unique aspect is its similar mass, color, and energy output to directly imaged planets.

Written By: Institute for Astronomy
continue to source article at ifa.hawaii.edu

22 COMMENTS

  1. PSO J318.5-22 was discovered during a search for the failed stars known as brown dwarfs. Due to their relatively cool temperatures, brown dwarfs are very faint and have very red colors. To circumvent these difficulties, Liu and his colleagues have been mining the data from the PS1 telescope. PS1 is scanning the sky every night with a camera sensitive enough to detect the faint heat signatures of brown dwarfs. PSO J318.5-22 stood out as an oddball, redder than even the reddest known brown dwarfs.

    It looks like a planet which has not (or not yet) accreted enough mass to become a brown dwarf star.

    I would guess that it has formed from an accretion disk with insufficient mass, or has escaped from some star system in a planetary sling-shot reorganisation, brought about by orbital resonances when interacting with other large planets or stars.

    • In reply to #2 by Alan4discussion:

      It looks like a planet which has not (or not yet) accreted enough mass to become a brown dwarf star.

      yep, i imagine there could be no end of objects like this

      just as brown dwarfs ave not accreted enough to become red dwarfs, which in turn….

      there could be whole mini-systems out there of small planets orbiting lonely gas giants, it’s all down to how much stuff there is about when some gas starts to collapse

  2. By regularly monitoring the position of PSO J318.5-22 over two years with the Canada-France-Hawaii Telescope, the team directly measured its distance from Earth. Based on this distance, about 80 light-years, and its motion through space, the team concluded that PSO J318.5-22 belongs to a collection of young stars called the Beta Pictoris moving group that formed about 12 million years ago. In fact, the eponymous star of the group, Beta Pictoris, has a young gas-giant planet in orbit around it. PSO J318.5-22 is even lower in mass than the Beta Pictoris planet and probably formed in a different fashion.

    If they have monitored it for two years they should also have an idea of its velocity, so it is not one of these very dangerous objects: -

    Hyperspeed Planets may move at up to 30 million miles an hour – http://news.nationalgeographic.com/news/2012/03/120323-runaway-planets-hyper-speed-loeb-harvard-space-science/

  3. The smallest brown dwarves known are 15 Jupiter masses, 2.5 times this fella. I always wanted to know if gas giants were too low mass to self ignite under gravity, could they nevertheless by lit by a big enough box of thermonuclear matches as imagined by Arthur C. Clarke?

    • In reply to #7 by phil rimmer:

      The smallest brown dwarves known are 15 Jupiter masses, 2.5 times this fella. I always wanted to know if gas giants were too low mass to self ignite under gravity, could they nevertheless by lit by a big enough box of thermonuclear matches as imagined by Arthur C. Clarke?

      Even if it were successfully lit by some sort of “nuclear spark plug”, isn’t the gravitational pull too weak to keep the whole thing together? What would prevent this mass of gas from inexorably expanding into space almost immediately after being lit? Isn’t a strong gravitational pull an essential ingredient for a self-sustaining thermonuclear star? And the only thing that can generate gravitational pull is mass.

      At least that’s my understanding of it… Am I missing something here?

      • In reply to #10 by NearlyNakedApe:

        Am I missing something here?

        No Its just that the Mass needed for ignition and the mass needed for sustained fusion might be different. and I’m too lazy to go look or attempt to work it out…

  4. Is there a way to know if this planet is travelling in a straight line or ellipse? It seems that if it is going in a straight line, sooner or later it would cause a catastrophic collision. What is in it’s pathway and can we predict an impact?

    BTW, it looks like the icon on The Hitchhiker’s guide!! It needs arms and a smile with a tongue sticking out. And maybe a coat of green paint.

    • In reply to #12 by crookedshoes:

      Is there a way to know if this planet is travelling in a straight line or ellipse? It seems that if it is going in a straight line, sooner or later it would cause a catastrophic collision.

      If it is in a star cluster, it will have its path bent by the gravity of any nearby stars as it orbits around the galactic centre.

      What is in it’s pathway and can we predict an impact?

      The distances between stars are huge, so there is probably nothing in its immediate path. It could be pulled into orbit around a star if it was passing close enough, but that would massively disrupt any planetary system there.

      There are probably lots of free floating planets and planetoids, but we can see this one because it is big enough for its nuclear reactivity to generate enough heat to be detected, (in the absence of a nearby star which would dazzle the instruments).

  5. Alan4,
    Very cool. So even if it was moving “straight”, it would be crooked (like my shoes) because of tugs on it along the way? How fast (approximately) would something like this be moving?

    • In reply to #15 by crookedshoes:

      Alan4,
      Very cool. So even if it was moving “straight”, it would be crooked (like my shoes) because of tugs on it along the way? How fast (approximately) would something like this be moving?

      If it is drifting in a young star-cluster, it will be moving with them at their orbital speed around the galaxy – plus or minus any individual differences.

      Velocities are relative, so there is a variety of answers. Here is the example of Earth which will differ slightly according to the position in the Milkyway Galaxy. !

      http://blogs.howstuffworks.com/2010/04/13/good-question-how-fast-are-you-moving-through-the-universe-right-now/

      Our solar system itself is also moving in an orbit around the galactic core. The solar system is something like 25,000 light years away from the center of the galaxy, and the galaxy makes one rotation every 250 million years or so. That gives the solar system a speed of something like 420,000 MPH or 675,000 KPH.

      Another result I found was that our galaxy and neighbors are moving at 600 km/s in the direction of the constellation Hydra (Scientific American). Finally, I found that the Milky Way moves through space within the cluster of galaxies it is a member of, and this cluster in turn moves through space towards yet another larger cluster of galaxies off in the direction of the constellation Virgo. This speed is approximately 300 km/s (Ask the Space Scientist).

      So there is speculation that the galaxy is moving through the universe at a speed of 1,000 km/s, which means 3,600,000 KPH or 2,237,000 MPH.

      Adding it all up, you get:

      1000 + 66,666 + 420,000 + 2,237,000 = 2,724,666 MPH

      Or

      1,610 + 107,000 + 675,000 + 3,600,000 = 4,383,610 KPH

      In other words, you are hurling through space at 2.7 million MPH (4.4 million KPH) even though it feels like you are sitting still.

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