Planet-Forming Disk Discovered Orbiting Binary System


Science fiction is lousy with examples of planets that orbit a system of two suns. Tatooine, in the Star Wars saga, is endowed with a pair of suns to light up the sky, as is the planet Magrathea in The Hitchhiker’s Guide to the Galaxy. It would indeed be quite a spectacle to wake up to more than one Sun every day for us who have only one. This sight may entirely be possible to view around the young binary star system V4046 Sagittarii, as new images from the Smithsonian’s Submillimeter Array (SMA) have confirmed the existence of a molecular cloud – which could harbor, or later produce planets –  orbiting the twin stars. This is the first time that evidence of planetary formation around a binary system of stars has been uncovered.

“We believe that V4046 Sagittarii provides one of the clearest examples yet discovered of a Keplerian, planet-forming disk orbiting a young star system,” said David Wilner of the Harvard-Smithsonian Center for Astrophysics in a press release issued today at the American Astronomical Society (AAS) meeting in Pasadena, Calif.

The disk has traces of carbon monoxide and hydrogen cyanide, gases that are telltale signs of planetary formation. It also lies between 30 -300 Astronomical Units from the central binary star system, a distance at which it is likely that our own giant planets Jupiter and Saturn formed, as well as the Kuiper belt objects. The two stars that make up the V4046 Sagittarii binary system are both approximately the mass of the Sun, and separated by a distance of 5 solar diameters.

Joel Kastner of the Rochester (NY) Institute of Technology, the lead scientist on the study, said in the press release“It’s a case of seeing is believing….We had the first evidence for this rotating disk in radio telescope observations of V4046 Sagittarii that we made last summer. But at that point, all we had were molecular spectra, and there are different ways to interpret the spectra. Once we saw the image data from the SMA, there was no doubt that we have a rotating disk here.”

Could this be the view of a sunset from a planet orbiting V4046 Sagittarii?
Could this be the view of a sunset from a planet orbiting V4046 Sagittarii?

The team of astronomers from the Harvard Smithsonian Center for Astrophysics and the Rochester Institute of Technology used the 30-meter radio telescope operated by the Institut de Radio Astronomie Millimetrique (IRAM) to pin down the the composition of the cloud, then used images from the Submillimeter Array to further confirm the finding. Both telescopes are sensitive to light in the submillimeter spectrum, which emanates from cold interstellar material such as gas and dust.

This new finding bodes well for the possibility that many other binary star systems harbor planets, and gives astronomers a new place to search for planets outside of our own solar system. Even better, V4046 Sagittarii is only 240 light-years away from our solar system, meaning that there’s a good chance that astronomers can image any planets that have already formed in the disk.

Source: AAS, Harvard-Smithsonian Center for Astrophysics

12 Replies to “Planet-Forming Disk Discovered Orbiting Binary System”

  1. Nice.

    You would have to assume that the orbital plane of the stars and that of the planet-forming disk would coincide. From any hypothetical planet then, the stars would eclipse each other regularly and often. That would make for some interesting temperature swings and weather patterns on such a planet, in addition to the usual day/night and seasonal cycles.

  2. yeah, i was thinking similar thoughts while reading. temperature/radiation variations in the habitable zone would present an interesting challenge to the development of life. certainly that scene from starwars, while very cool looking, is highly unlikely.

  3. Somewhere in the deep space of my brain I think I remember a strory that astronomers found a four-star-system with at least one planet – but probably I remember falsely.

    On the other hand, of course it is much more interesting to find the proto-planetary disk. It’s amazing where stable orbits are possible…

  4. I think I remember that 4-star system too, but the planet was only orbiting one of those stars, which were much farther apart. (I could be mis-remembering,though!)

    If the two stars are both G-class, then i would think that the “water zone” would be more distant and wider than Sol’s. That would give a greater margin for habitable planets, or moons of gas planets.

    I also wonder how the two stars interact electromagnetically, given their proximity to each other. I’m thinking there should be some interesting star spots and flares, at least.

  5. Talking of science fiction: You forgot Solaris. No spectacular sunsets on this one, though.

  6. And if we’re including written sci-fi, Asimov’s “Nightfall” is perhaps the most important example! Great story. It’s short too, and can be found online. An exploration of psychology, epistemology, and astronomy all in one.

    I’m starting to sound like an advert now eh. 😛

  7. I should also say that I can only speak for the short story form of “Nightfall,” which is the original tale. The novel was done later, and probably just added unnecessary bloat to the story.

  8. @DrFlimmer and Dark Gnat-
    that story about the four stars is one of the “Related Stories” just above this comments section.

  9. @cipater: I can think of no more illustrative story on this topic other than Asimov’s “Nightfall” and you are right to bring it up at this site. Among those who have read it, it is legend. Among those yet to peruse this short story, a pleasant surprise awaits.

  10. highly unlikely

    Well, less highly unlikely then. The probability of life jumps quite drastically between ordinary space and planets. 🙂

  11. good point. but when i wrote “highly unlikely”, i was referring mostly to how the stars appeared in the sky during the star wars shot, not so much as to whether or not life could form around a binary system; although my personal opinion is, as stated, in agreement with astrofiend’s comment.

    there are many unexplored reasons why most binary systems would be greatly inhospitable to life.

    george lucas brings space to life for many people and that’s a good thing, but his representations of space suffer from most of the typical hollywood weaknesses.

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