Astronomers Image Lowest-mass Exoplanet Around a Sun-like Star

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Using infrared data from the Subaru Telescope in Hawaii, an international team of astronomers has imaged a giant planet around the bright star GJ 504. Several times the mass of Jupiter and similar in size, the new world, dubbed GJ 504b, is the lowest-mass planet ever detected around a star like the sun using direct imaging techniques.


"If we could travel to this giant planet, we would see a world still glowing from the heat of its formation with a color reminiscent of a dark cherry blossom, a dull magenta," said Michael McElwain, a member of the discovery team at NASA's Goddard Space Flight Center in Greenbelt, Md. "Our near-infrared camera reveals that its color is much more blue than other imaged planets, which may indicate that its atmosphere has fewer clouds."

GJ 504b orbits its star at nearly nine times the distance Jupiter orbits the sun, which poses a challenge to theoretical ideas of how giant planets form.

According to the most widely accepted picture, called the core-accretion model, Jupiter-like planets get their start in the gas-rich debris disk that surrounds a young star. A core produced by collisions among asteroids and comets provides a seed, and when this core reaches sufficient mass, its gravitational pull rapidly attracts gas from the disk to form the planet.

Written By: NASA
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  1. Several times the mass of Jupiter and similar in size, the new world, dubbed GJ 504b, is the lowest-mass planet ever detected around a star like the sun using direct imaging techniques.

    It’s good to see that direct imaging techniques are picking out progressively smaller planets.

    GJ 504b orbits its star at nearly nine times the distance Jupiter orbits the sun,

    It is also good to see that they can pick out planets which are at a distance from their stars. Other techniques, tended to pick the easy targets which were very close to their stars.

    which poses a challenge to theoretical ideas of how giant planets form.

    Perhaps they will find other giant planets with which it has interacted to move it into a more distant orbit from its star – rather like the cataclysm which moved Uranus and Neptune and rearranged the outer Solar system.

    http://lunarscience.nasa.gov/articles/the-solar-systems-big-bang/

    In the theory, the four biggest planets — Jupiter, Saturn, Neptune and Uranus — initially had sedate, circular orbits and were packed into a region only about half the diameter of Neptune’s average modern orbit. Gravity then caused these bodies to spread out and break into a planetary version of bowling that not only violently rearranged the outer solar system but also led to an avalanche of debris pelting the inner planets and their moons.
    Prompting this melee, scientists propose, was a series of gravitational interactions between the planets and the hefty disk of debris that lay just beyond. This disk, a forerunner of the Kuiper Belt, contained as much mass as 35 Earths.

    For a while, not much happened. Jupiter moved slowly inward while the three other planets moved slightly outward. Then, at about 500 million to 600 million years after the birth of the solar system, Jupiter and Saturn hit a gravitational sweet spot, with Jupiter going around the sun twice for every orbit of Saturn.

    In this configuration, known as an orbital resonance, the mutual gravitational influence of the two giants strengthened, elongating their orbits over time. The changed paths of Jupiter and Saturn eventually jumbled the orderly, circular orbits of the two lighter-weight, outermost giants, Uranus and Neptune. And that’s when all hell broke loose, Levison says.

    Within a few million years, Uranus and Neptune were kicked so far out that they plowed into the surrounding disk of icy debris. Like bowling balls scattering pins, the two planets scattered the debris all over the solar system.

    • In reply to #4 by Net:

      and now “image” is a verb? science progresses; language deteriorates – well at least the language of journalism deteriorates.

      Actually, in Astronomy we have been talking about ‘astro-imagers’ for some time. I am both a planetary imager and a deep-sky imager! (very different techniques). I guess it has come about because of the fact that so many astro images are false colour. It also became te norm as more of us went over to using CCDs rather than film (when we were astrophotographers!)

      [Link to own website removed by moderator]

      Ian.

  2. In this article, does ‘lowest mass’ actually mean ‘lowest density’ ? Then it goes on to say that it is … ‘Several times the mass of Jupiter and similar in size’ but that would make jupiter less dense than this newly discovered planet. I seem to be missing something?

    • In reply to #5 by old-toy-boy:

      In this article, does ‘lowest mass’ actually mean ‘lowest density’ ?

      It is simply referring to the gross mass of the planet being smaller than any exoplanet previously directly imaged.

      Then it goes on to say that it is … ‘Several times the mass of Jupiter and similar in size’ but that would make jupiter less dense than this newly discovered planet. I seem to be missing something?

      This is suggesting it has a greater density than Jupiter, Which could arise from greater compression from the higher gravity of the greater mass, or could involve a greater proportion of heavy elements in its composition.

  3. In reply to #6 by isharp:

    In reply to #4 by Net:

    and now “image” is a verb? science progresses; language deteriorates – well at least the language of journalism deteriorates.

    Actually, in Astronomy we have been talking about ‘astro-imagers’ for some time. I am both a planetary imager and a deep-sky imager! (very different…

    People generally do not invent completely new words, they recycle bits of old words, link them with other word fragments, make nouns into verbs or vice-versa, borrow from other languages, tack unexpected endings onto words to form new meanings. “Popering” was a good (joke) word coined here by DHudson the other day. “Contradiction” was a word co-opted from language studies, by Karl Marx, to denote a metaphysical notion, far divorced from its original meaning in the study of argument and rhetoric.

    Science and most other academic disciplines require a technical language, and it is not possible to invent completely new sound sequences to convey new meanings, so they cannibalise. This is how language develops and becomes the infinitely flexible tool we have, able to produce the astounding poetry of Shakespeare, Homer and Yeats, as well as the technical language of modern science, which is able to carry concepts of such arcane obscurity, that most people are quite unable to grasp them at all.

    The language which is prone to become obscure, and almost entirely metaphorical, because it is mostly devoid of real meaning or intellectual content, is of course the language of business and government. Not only is this language designed to mask meaning, and confer intellectual status and group leadership on the user, it is also ugly, and completely meaningless, or at least of such simple meaning, that the concepts behind it could easily be carried by the ordinary language of discourse. Sometimes it is known as “power language.”

  4. Maybe the core-accretion theory doesn’t help here because this planet formed seperately as a wannabe star. Anyway, if this sun like star GJ 504 is hardly visible at 57 ly distance, imagine the other way round. Our sun is about to disappear for human eyes by the same distance. We “now” could just see the year 1956 (Elvis’ Heart Brake Hotel)

    http://en.wikipedia.org/wiki/1956

    • In reply to #9 by layer8:

      Maybe the core-accretion theory doesn’t help here because this planet formed seperately as a wannabe star.

      Accretion disks and stars can form in clusters, so a large planet which did not grow enough to participate in a binary star system as a star, should be feasible.

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