Tight Binaries are ‘Death Stars’ for Planets

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Astronomers studying double star systems where the two stars are extremely close have found a pattern of destruction. While there probably isn’t a Star Wars-like Death Star roaming the Universe, tight binary systems might provide the equivalent of Darth Vader’s favorite weapon. “This is real-life science fiction,” said Jeremy Drake of the Harvard-Smithsonian Center for Astrophysics. “Our data tell us that planets in these systems might not be so lucky — collisions could be common. It’s theoretically possible that habitable planets could exist around these types of stars, so if there happened to be any life there, it could be doomed.”

Using the Spitzer Space Telescope, Drake and his team spotted a surprisingly large amount of dust around three mature, close-orbiting star pairs, that might be the aftermath of tremendous planetary collisions.

Drake is the principal investigator of the research, published in the Aug.19 issue of the Astrophysical Journal Letters.

The particular class of binary stars in the study are extremely close together. Named RS Canum Venaticorums, or RS CVns for short, they are separated by only about 3.2-million kilometers (two-million miles ), or two percent of the distance between Earth and our sun. The binaries orbit around each other every few days, with one face on each star perpetually locked and pointed toward the other.

These stars are familiarly like our own Sun – about the same size and probably about a billion to a few billion years old — roughly the age of our sun when life first evolved on Earth. But these stars spin much faster, and, as a result, have powerful magnetic fields, and giant, dark spots. The magnetic activity drives strong stellar winds — gale-force versions of the solar wind — that slow the stars down, pulling the twirling duos closer over time.

This is not a good scenario for planetary survival.

As the stars cozy up to each other, their gravitational influences change, and this could cause disturbances to planetary bodies orbiting around both stars. Comets and any planets that may exist in the systems would start jostling about and banging into each other, sometimes in powerful collisions. This includes planets that could theoretically be circling in the double stars’ habitable zone, a region where temperatures would allow liquid water to exist. Though no habitable planets have been discovered around any stars beyond our sun at this point in time, tight double-star systems are known to host planets; for example, one system not in the study, called HW Vir, has two gas-giant planets.

“These kinds of systems paint a picture of the late stages in the lives of planetary systems,” said Marc Kuchner, a co-author from NASA Goddard Space Flight Center. “And it’s a future that’s messy and violent.”

The temperatures around these systems measured by Spitzer are about the same as molten lava. The astronomers says that dust normally would have dissipated and blown away from the stars by this mature stage in their lives. They conclude that something — most likely planetary collisions — must therefore be kicking up the fresh dust. In addition, because dusty disks have now been found around four, older binary systems, the scientists know that the observations are not a fluke. Something chaotic is very likely going on.

If any life forms did exist in these star systems, and they could look up at the sky, they would have quite a view. Marco Matranga, lead author of the paper, also from Harvard-Smithsonian said, “The skies there would have two huge suns, like the ones above the planet Tatooine in ‘Star Wars.'”

The research was published in the Aug.19 issue of the Astrophysical Journal Letters.

Source: JPL

14 Replies to “Tight Binaries are ‘Death Stars’ for Planets”

  1. The stellar pairs orbit around each other every few days, with one face on each star perpetually locked and pointed toward the other.

    While it’s generally understood that stellar surfaces are not as rigid as that of a planetary body’s, I wonder what the quoted statement means.

  2. tight binary systems might provide the equivalent of Darth Vader’s favorite weapon.

    I wish to make a complain: Darth Vader was never fond of the Death Star. From the first movie (which is episode 4 for all the young kids here 😉 ) we know what he says about it:

    “Don’t be too proud of the technological terror you’ve constructed. The ability to destroy a planet is insignificant next to the power of the force!”

  3. The analogy is more to Heinlein’s linear accelerator that the Lunies used to pummel Earth with.

    A favorite weapon of Darth Vader, the Death Star was not.

    The first one nearly got him killed when he had to defend it, and to top that it exploded nearby while he was managing a damaged craft.

    Also, Vader wasn’t in with the mass terror and killings that some Imperial fleet commanders were fond of using. The Sith was interested in personal power, AFAIU. The impression I got was that the emperor used fascism because he had to. Which made him more evil, using evil politics for even more worse gains.

  4. The speed at which these stars orbit each other is phenomenal, and the short distance between them is mind boggling.

    On a different note, I am wondering if it is possible for the sun to eject a part of its internal core and send it speeding toward earth. I am talking about a solid mass like a chunck of rock, not something like a CME.

  5. At these tight distances any planets around such a binary system would be far removed from both. Any object orbiting exclusively around either star would be in an unstable orbit. Classical mechanics does not give integrable solutions in closed form for systems with more than 3 bodies. For three equal mass objects that interact by some force, such as gravity, the orbits are highly chaotic — except for a few exceptional cases. Such an exceptional case would be three exactly equal masses arrayed from each other on an isosceles triangle. Even though that solution is “stable” the smallest perturbation on it will cause it to go unstable. In the case of binary stars in .05AU orbits around each other, planets at 1AU and further out will not be terribly effected by the dipole oscillation of the pair and could then be stable.

    LC

  6. if the sun has a tiny low mass nemesis compansion star that is responsible for 14 major predictable mass extinctions in earths past, then it doesn’t look good for habitable planets in the universe that are supporting life to be on a lesser mass binary star system where dipole oscillations are greater. Such a planet could be thrown out into cold outer space or into the larger companion star. Imagine the view

  7. @ Billy_Stanley:

    eject a part of its internal core

    I wouldn’t expect that in a normal star like the sun, since the pressures and densities involved are enormous. It takes hundreds of thousands of years for a photon to make it’s way out from the fusion core and become visible light.

    When stars explode at depth, it’s a global phenomena. Most supernova explosions seems to be surface phenomena, at that. (Of course, that depends on the environment – close binaries to suck matter from et cetera – but precisely therefore some indication of the rareness of the deep explosions.)

  8. @NAVNEETH,

    Although JPL’s “Feedback” states, “Due to the volume of mail, we generally are not able to respond individually”, I’ll gladly let you (and everybody else here) know if I receive a response from them.

  9. @ Billy_Stanley:

    An inner core that would be ejected into space would become a gas just like a CME.
    The inner core is dense because of the pressure, once in outer space there is no pressure compressing it that dense.

  10. This business about the sun ejecting it core is wrong. Star eject their outer layers, not their core.

    LC

  11. If planets can form in a tight binary system – do they orbit outside the binary star’s orbit?
    I am having a tough time envisioning where a planet could exist in that type of a system…….
    Anybody???

  12. Is there not an inherent contradiction in saying
    (a) “The stellar pairs orbit around each other every few days, with one face on each star perpetually locked and pointed toward the other.
    and
    (b) “These stars spin much faster much faster than our sun”?

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