New Rogue Planet Found, Closest to our Solar System

Article written: 14 Nov , 2012
Updated: 23 Dec , 2015

This artist’s impression shows the free-floating planet CFBDSIR J214947.2-040308.9. Credit: ESO/L. Calçada/P. Delorme/Nick Risinger/R. Saito/VVV Consortium

Rogue planets – also known as free floating planets – are pretty intriguing. They are not orbiting a star but instead are wandering through the galaxy, having been either forcibly ejected from a solar system or having formed very early on in the Universe. While only a handful of these planets have been actually found, astronomers estimate these vagrant worlds could vastly outnumber stars. In fact, it’s been suggested there could be 100,000 times more rogue planets than stars in our Milky Way galaxy alone!

The latest rogue world to be found is exciting in that it is the closest such object to our Solar System so far. At a distance of about 100 light-years, its comparative proximity, along with the absence of a bright star very close to it, has allowed the team to study its atmosphere in great detail. Astronomers say this object gives them a preview of the exoplanets that future instruments will be able to find – and potentially take image of — around stars other than the Sun. But the planet also seems to be loosely tied to a roving group of stars, called the AB Doradus Moving Group.

The new rogue planet, with the ungainly name of CFBDSIR J214947.2-040308.9 (CFBDSIR2149 for short), was found using the Very Large Telescope and the Canada-France-Hawaii Telescope. The astronomers, led by Philippe Delorme from the Institut de planétologie et d’astrophysique de Grenoble, CNRS/Université Joseph Fourier, France, are calling the object a rogue planet candidate for now, as they want to study it further to confirm its free-floating status.

Moving star systems are equally intriguing. The AB Doradus Moving Group is the closest such group to our Solar System, and the stars drift through space together in a pack. They are thought to have formed at the same time. If the new rogue planet actually is associated with this moving group, astronomers say it will be possible to deduce much more about it, including its temperature, mass, and what its atmosphere is made of. There remains a small probability that the association with the moving group is by chance.

The link between the new object and the moving group is the vital clue that allows astronomers to find the age of the newly discovered object. Without knowing its age, it’s not possible to know whether it is really a planet, or a brown dwarf, a “failed” star that lack the bulk to trigger the reactions that make stars shine.

This is the first isolated planetary mass object ever identified in a moving group, and the association with this group makes it the most interesting free-floating planet candidate identified so far.

This closeup of an image captured by the SOFI instrument on ESO’s New Technology Telescope at the La Silla Observatory shows the free-floating planet CFBDSIR J214947.2-040308.9 in infrared light. This object, which appears as a faint blue dot at the centre of the picture, is the closest such object to the Solar System. Credit: ESO/P. Delorme.

“Looking for planets around their stars is akin to studying a firefly sitting one centimetre away from a distant, powerful car headlight,” said Delorme. “This nearby free-floating object offered the opportunity to study the firefly in detail without the dazzling lights of the car messing everything up.”

Free-floating objects like CFBDSIR2149 are thought to form either as normal planets that have been booted out of their home systems, or as lone objects like the smallest stars or brown dwarfs. In either case these objects are intriguing — either as planets without stars, or as the tiniest possible objects in a range spanning from the most massive stars to the smallest brown dwarfs.

“These objects are important, as they can either help us understand more about how planets may be ejected from planetary systems, or how very light objects can arise from the star formation process,” says Philippe Delorme. “If this little object is a planet that has been ejected from its native system, it conjures up the striking image of orphaned worlds, drifting in the emptiness of space.”

If CFBDSIR2149 is not associated with the AB Doradus Moving Group, the astronomers say it is trickier to be sure of its nature and properties, and it may instead be characterized as a small brown dwarf. Both scenarios represent important questions about how planets and stars form and behave.

“Further work should confirm CFBDSIR2149 as a free-floating planet,” said Delorme. “This object could be used as a benchmark for understanding the physics of any similar exoplanets that are discovered by future special high-contrast imaging systems, including the SPHERE instrument that will be installed on the VLT.”

This video shows an artist’s impression of the free-floating planet CFBDSIR J214947.2-040308.9. In the first part of the sequence the planet appears as a dark disc in visible light, silhouetted against the star clouds of the Milky Way. This is the closest such object to the Solar System and the most exciting candidate free-floating planet found so far. It does not orbit a star and hence does not shine by reflected light; the faint glow it emits can only be detected in infrared light. In the final sequence we see an infrared view of the object with the central parts of the Milky Way as seen by the VISTA infrared survey telescope as background. The object appears blueish in this near-infrared view because much of the light at longer infrared wavelengths is absorbed by methane and other molecules in the planet’s atmosphere. In visible light the object is so cool that it would only shine dimly with a deep red colour when seen close-up.

Read the team’s research paper here (pdf).

Source: ESO

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20 Responses

  1. DarkGnat says

    I think the line between a low mass brown dwarf and free floating “planet” is a blurry one.

    Also this throws another monkey wrench into the proper definition of a “planet”. This could be a “planemo” I suppose.

    Good find!

    • Maybe a plar or a stanet!

    • Torbjörn Larsson says

      There is no “proper” definition of a planet, there are many definitions suiting different situations.

      But there is an official IAU definition of planet. The IAU definition is only relevant for our own system, because of the observational requirements: “in the Solar System“.

      These planets are exoplanets. They are mostly defined by the many ways we observe them at the moment.

      Yes, “planemo” would suit: “the purpose of the term is to describe objects which do not conform to typical expectations for a planet. These include … free-floating planets not orbiting a star, such as rogue planets ejected from their system, …”.

      • zetetic elench says

        I wonder about the possibility of moons around such objects. Why not? Even if they were ejected from proto-disks they could be included in the interaction. There are certainly multiple formation scenarios that would result in rogue status. They may have disks of their own, in other words.

      • Torbjörn Larsson says

        And if ice moons, which would be likelier as rouges would preferably be ejected from the outer parts of a system*, they could be habitable.

        * See the “ejected 5th giant” extension of the current Nice model predicting our own system.

  2. Walter_Peterson says

    What constellation is it in?

    • JonHanford says

      Aquarius (RA 21 49 47.2 Dec -04 03 08.9)

      • Member
        Aqua4U says

        I took a cursory look around and found that the CFHT has a limiting magnitude range of about 25-27 mag. in red light. The VLT even better? TBD? Another fine reason to get the ‘James Webb Space Telescope’ up and running!

  3. Torbjörn Larsson says

    This is so neat! The AB Doradus Moving Group has ~ 30 stars in it, so this observation (if confirmed) is already pushing up against the “1 rogue for 1 system” constraint of microlensing.

    If we hadn’t observed such an object soon, we would have strained the microlensing observations. In practice, our system has met many of these nearby, and we are quite unlucky to not have anyone closer as of yet.

    So, another win for the exoplanet hunters, on its lonesome and as testing earlier predictions.

  4. Kawarthajon says

    Must be incredibly hard to find these things ’cause they’re so dim. Also says that the atmosphere was studied extensively, but nothing else was said about it. Any info about the atmosphere, how big the planet is, how hot/cold it is?

    BTW, love the name for the planet and all, but maybe we could come up with something a little more catchy.

    • Torbjörn Larsson says

      – If you follow the link, and accept the likely correlation to the group:

      “The association with the AB Doradus Moving Group would pin down the mass of the planet to approximately 4–7 times the mass of Jupiter, with an effective temperature of approximately 430 degrees Celsius. The planet’s age would be the same as the moving group itself — 50 to 120 million years.”

      “The team’s statistical analysis of the object’s proper motion — its angular change in position across the sky each year — shows an 87% probability that the object is associated with the AB Doradus Moving Group, and more than 95% probability that it is young enough to be of planetary mass, making it much more likely to be a rogue planet rather than a small “failed” star. More distant free-floating planet candidates have been found before in very young star clusters, but could not be studied in detail.”

      So it’s not even a 2 sigma observation as of yet, but it would be a fair diagnosis at your hospital (~ 80 % average diagnosis accuracy), and good enough to bet on. But Delorme promises us better data in the future.

      – “Want to Name an Exoplanet? Uwingu Has a Plan“, a recent UT tip.

      • Kawarthajon says

        I did look at the article, but I do not have a science background and got pretty lost after the first couple of paragraphs – I did not have the patience to glean the few pieces of info I might have understood. Thanks for dissecting out that info for me!

      • Torbjörn Larsson says

        No planem… hay problema!

  5. Member
    Aqua4U says

    I think they ought to name this planet ‘Neburu’.. just to stir up the ‘paranoid psychics’ in the crowd? Hmmmmm…. then laughs at the coincidental and seemingly synchronistic nature of this find? UGH!

  6. katesisco says

    Ok, is strange to think of this ‘group’ instead of a solar system, but they must be orbitally bound right? These 7 or so suns? So is the dogie planet orbiting some, one , several?

    So this is really a system on the run? I like that so much better than moving group. But since you see it by its sun’s movements, it is not found by gravitational lensing is it? I am rather fond of Miles Mathis explanation for refracting light due to dust and gas. It seems science has id’d gas clouds and dust rings everywhere so gravitational lensing is passe.

  7. torque xtr says

    And still no data from WISE on such ones. Maybe there are not only Neburus in the distant open clusters but also Yuggoths in our Oort Cloud backyard… ha!

    One such thing in a 200 ly-across volume is much, much rarer than normal stars. Even accounting for observational bias, if only 100 megayear-or-less old planets are detected (x50), less massive are more likely to be ejected, and only the volume of AB Doradus cluster is scanned (x150), there is a pretty high chance that alpha Cen Bb is the closest terrestrial-mass world after Venus, Mars and Mercury…

    • Torbjörn Larsson says

      We already know from microlensing surveys that they are about as frequent as stars. Our system would meet them fairly often. And if they are as large or larger than Jupiter their residual heat would show up for billions of years.

      That would still mean your last estimate is good though.

  8. briansheen says

    Prefer Orphan planets as a collective, however how can any sort of estimate be made with ANY confidence from such a small sample ?

    • Torbjörn Larsson says

      In this case the observation combines with an earlier microlensing survey, which had fairly good confidence. (See my earlier comment for more.)

      The microlensing surveys relies on searching many possible events, so even if they only turn up a handful of events they give good confidence.

  9. Torbjörn Larsson says

    Q: “7 or so suns”.

    A: ~ 30 stars (see my previous comments).

    Q: “orbiting”.

    A: Likely no, but still open question (see the article).

    C: “since you see it by its sun’s movements”.

    A: No, by emission (see the article).

    C: ” Mathis explanation for refracting light due to dust and gas.”

    Dust and gas refracts light, but that has nothing to do with gravitational lensing, an often occurring phenomena which is readily separated from other mechanisms.

    C: “gravitational lensing is passe”.

    No. This is for example how we know the frequency of rogues (see my previous comments).

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