Homey-Looking Alien Star System May Host 7 Planets

By Andrew Moseman | August 25, 2010 10:53 am

NewStarSystemIn August 2006, Pluto received its official demotion to dwarf planet status, taking our solar system down to eight planets. In August 2010, exoplanet hunters say they’ve found a haul of new worlds around a single star; that alien solar system may have seven known planets, meaning the system could be more like our home system than any ever discovered. And one of those worlds could be the smallest exoplanet ever found, too.

The star these planets orbit is called HD 10180, and it lies 127 light years from here. Astronomers at the European Southern Observatory in Chile used a spectrograph called HARPS to track tiny variations in the starlight caused by the pull of the planets.

It found clear evidence for five giant planets similar in size to Uranus or Neptune in our own solar system. But there were also tantalising signs that two other planets are also present, one of which would be the smallest, or least-massive, yet found orbiting another star [Christian Science Monitor].

While those gas planets would be at least 13 times the size of the Earth, the small world—if it’s truly there—would contain less than one and a half Earth masses. But as astronomers have seen with many of the small exoplanets they’ve found, Earth-size doesn’t mean Earth-like when it comes to temperature, chemical composition, or anything else. The HARPS data suggests this roughly Earth-size planet is scaldingly close to the star: Its year is just more than one of our days.

And, as we saw last month when one of the scientists behind the planet-hunting Kepler mission got everyone excited over Earth-size planet “candidates,” it can take a long time to confirm the finding of smaller, rocky worlds. Astronomer Alan Boss agreed:

Boss noted that the method was “biased toward finding the big guys” because the greater the planet, the greater its gravity and the more it made its parent star wobble. But he said the discovery showed that finding smaller planets was still possible. “This field has gone from zero to close to 500 planets in just 15 years,” he said. “Fifteen years ago we did not know about the big guys. Earth-like planets are going to be quite commonplace” [AP].

Whether this star system has five or seven planets, it shows that astronomers are creeping closer to finding systems that look like ours. National Geographic reports that just 15 known systems have three planets or more, but that number might soon shoot upward. Next year the Kepler scientists are supposed to release their full data set from the telescope’s first batch of findings, including the Earth-sized candidates they’ve been holding back. And, on a more basic level, every year since the first exoplanet discovery, astronomers have spotted more of them than the year before.

As the planet count rises, we’ll probably see solar systems that resemble home on more sophisticated levels. HD 10180 might have about the same number of planets as our sun, but the system itself is markedly different: Those Neptune-sized gas planets orbit much closer than Neptune, and there doesn’t appear to be a Jupiter-sized giant in the group. The gravitational influence of a huge gas giant can especially influence the prospects for life:

Studies have shown that Jupiter, with its gassy enormity, has been acting as a sort of shield for Earth, gravitationally deflecting asteroids and comets that hold the potential to trigger mass extinctions [National Geographic].

So there’s no place quite like home… yet.

Related Content:
80beats: Kepler’s Early Results Suggest Earth-Like Planets Are a Dime a Dozen
80beats: Astronomers Find a Bevy of Exoplanets; Won’t Discuss Most Interesting Ones
DISCOVER: How Long Until We Find a Second Earth?
Bad Astronomy: Another Jupiter Impact?

Image: ESO / Davide De Martin

  • Torbjörn Larsson, OM

    Already the Kepler data filled in the missing gaps, so that we could say that the solar system wasn’t unique. (It’s a long list: star metallicity, planet “dynamical packed”, asteroid belts and comets, …) But that was at the time with a 5 planet system most numerous, this tops that.

    Whether this star system has five or seven planets

    FWIW the press release is a FAIL. The paper actually summed to six signals with plausible strength. And that was the number of exoplanet candidates entered into an official database for HD10180.

  • Torbjörn Larsson, OM

    Studies have shown that Jupiter, with its gassy enormity, has been acting as a sort of shield for Earth, gravitationally deflecting asteroids and comets that hold the potential to trigger mass extinctions

    I find that potential or the sterilizing potential unlikely to crystallize, for 3 reasons:

    – There is a modern model paper that shows that any existing thermophiles and likely even mesophiles easily survived our own Last Heavy Bombardment. (Which doesn’t seem to have had crust busters in their model.)

    – The LHB was caused by our giant planets migration, not the best possible scenario.

    – Only one asteroid can be attributed to a mass extinction, and it happened because it rather unluckily hit minerals (calciferous and sulfurous) caused by modern life. ~ 0.5 Gy earlier and it wouldn’t have mattered. ~ 0.5 Gy later and it won’t matter (biosphere dead or dying from expanding sun heating). A small window and one unlucky shot, so small likelihood.

  • http://laurele.livejournal.com Laurel Kornfeld

    Our solar system does NOT have only eight planets. Please stop presenting one side of an ongoing debate as fact when it is not. The decision by four percent of the IAU is not any more “official” than the decision of several hundred professional astronomers who rejected that demotion. The New Horizons mission to Pluto continues to refer to Pluto as a planet. Conferences and papers continue to discuss this issue, and it is only fair to the public to present both sides. And according to the opposing side, a planet is a non-self-luminous spheroidal body orbiting a star. That gives us at least 13 planets and counting. Dwarf planets are planets too. Stern, the person who created the term dwarf planet, intended it to describe a third class of planets that are large enough to be in hydrostatic equilibrium but not large enough to gravitationally dominate their orbits. He never intended for dwarf planets to not be considered planets at all. When the IAU precluded dwarf planets from being considered planets, they misappropriated Stern’s term to create a definition that is highly problematic and makes little sense.

  • http://desktopeer.blogspot.com Eagle

    I must congratulate the scientists for finding another planetary system. But alas, it’s quite far away. 127 light years is no small distance and the only scientifically speediest thing yet known is light which takes 127 years to reach that planet. So I don’t think it’s very profitable. Yet it will be added to records and the names of the scientists who found the system would be written in it too. But wouldn’t it be great if they do something for the mankind too which is near a disaster materialistically and spiritually?

    Anyways, I came across a cool post regarding the space technology, I suggest you to read it too! :)

  • Brian

    I never understood the whole “Pluto isn’t a planet, it’s a dwarf planet” thing. I mean, isn’t a dwarf planet still a planet? Just because it’s not as big as other planets, doesn’t mean it isn’t still part of the planet family. The term “dwarf planet” was created to give smaller planetary bodies a group to belong to, wasn’t it? Just like the term “gas giant” was created to describe massive, gaseous planetary bodies.

    I just don’t understand the debate, especially now that we’re on the verge of discovering more potential “dwarf planets” that lie beyond Pluto. Are we going to have heated debates about all of them? I wish the scientific community would just come to an agreement on the labeling of small planets already.

    As for this article, I heard about it on SpaceRip a couple days ago, and I think it’s great. The system is almost identical in makeup to our own, which means there is a high possibility that organic life has evolved, or has existed there at one time. The fact that the star is similar to the Sun means that the planets in the “habitable zone” won’t be bombarded with massive amounts of radiation like the planets in the famous Gliese system. That means, that if there is a rocky planet in the habitable zone of HD10180, they could have climates very similar to Earth’s, or at least be able to sustain liquid water. It’s very exciting, can’t wait to hear more about this system!

  • amphiox

    Re #3;

    This isn’t a relevant place for that particular rant, right or wrong. In terms of comparison with extrasolar solar systems, there are eight planets, and only eight planets, in this one. (And frankly, if one wants to be really rigorous, there are only four). Because if our solar system was observed with the same methods used to detect the extrasolar planets, chances are we would only detect the four outer planets. (Kepler presumably would be able to detect at least some of the inner planets, maybe all eight). But there is absolutely nothing currently available that has any reasonable chance of detecting anything equivalent to the dwarf planets as individual worlds orbiting other stars. The closest we can come right now is detecting the discs and belts of debris in which they might reside.

    It is the comparison that makes this research interesting, and comparisons are only valid if you compare equivalent things. If you are talking about comparing planet numbers between extrasolar systems and our own in terms of planet numbers, including the dwarf planets invalidates the comparison. We should expect, if our theories on solar system formation are true, that all those extrasolar systems should have multiple dwarf planets that we cannot detect.

    I’m getting really tired of people throwing hissy fits over naming conventions. A name is just a name. Pluto didn’t change one whit after the classification changed, and won’t change one whit if one day we change it again. Names matter only so far as they are useful for organizing knowledge and communicating information. For New Horizons, including dwarf planets in the definition of planets obviously matters and is arguably useful. For comparisons with extrasolar planets at this present time, including dwarf planets in the definition of planet is useless and actually misleading, and therefore should not be done.

  • m

    127 ly away. seems we should think about sending a probe out now.

    our decendants 5,000 years from now will thank us.

  • Donna

    Nicely said amphiox:)

  • Ryan

    the reason we need to search for exoplanets is because once we find earth like planets (which I personally am confident we will) we will be that much closer to proving life in the universe is not limited to earth (another thing i am confident will happen). Contrary to your assertion of this not contributing to our spiritual well being, quite the opposite is true. For once we prove life is abundant we can break free of the outdated spiritual chains by which we continue to be bound and realize the true nature of our existence.

  • Messier Tidy Upper

    @3. Laurel Kornfeld : I agree.

    If a dwarf star is still counted as a star – and 90% of all stars are main-sequence dwarfs then why the blazes do we not count dwarf planets as planets in the exact same way? Eh?

    Plus if we put Earth – or even Jupiter – out where Pluto is then it would cease being a planet by IAU fiat. Alternatively if we (hypothetically) moved Pluto to the inner Solar system – say just around Mars or between Earth and Venus – then it suddenly *would* become an “official” planet and as Ken Croswell points out on his website a really bright one!

    So the IAU definition is illogical and, frankly, ridiculous. The IAU definition fails the reductio ad absurdum test.

    Way I see it, a planet is a natural object that is :

    1. Large enough to be round (or ellipsoidal for fast rotators eg. Haumea) through its own gravitational strength. (Thus not an asteroid or comet type body.)

    2. Not so large that it is ever able to fuse hydrogen, helium or deuterium and thus become a star or brown dwarf.

    3. In a direct orbit around its primary star or common barycentre for double planets rather than directly orbiting another planet. (Thus not a moon.)

    That’s it. A simple, easy and effective definition. Why doesn’t the IAU see sense and adopt that definition or something like it rather than their current unpopular, illogical and inconsistent one?

    BTW. The IAU definition doesn’t even count planets of other stars only our Sun so the title of this post – and most articles, etc .., on this and other exoplanetary discoveries are *already* essentially ignoring and rejecting the IAU’s definition.

    Names *do* matter to many people as this debate here proves. We do need to know – quite literally – what we’re talking about! 😉

    Our solar system then has a large number of planets of three main types : the rocky, the gassy and the icy! Most planets in our own solar system are icy and Pluto is one of the larger ones. Larger than Makemake, Quaoar, Sedna, Orcus, Varuna, Haumea, “Buffy”, etc .. 😛


    Back on the immediate topic :

    Thanks 80Beats – great news, nice article & you’ve beaten the Bad Astronomer to it! Well done! :-)

  • http://laurele.livejournal.com Laurel Kornfeld

    “In terms of comparison with extrasolar solar systems, there are eight planets, and only eight planets, in this one. (And frankly, if one wants to be really rigorous, there are only four). Because if our solar system was observed with the same methods used to detect the extrasolar planets, chances are we would only detect the four outer planets. ”

    Your first and second sentences contradict one another. In your view, is the number four or eight? The reality is, the number depends on our level of technology regarding what we are able to detect. You’re correct in saying that if our solar system were observed with the same methods we use for detecting exoplanets, we would find only four. However, that doesn’t mean our solar system has only four planets; it just means we cannot detect any others (specifically, anything smaller than an ice giant). Eventually, this will change, and our detection systems will be capable of finding both terrestrial planets and dwarf planets in other solar systems. It is important not to confuse what we can see with the reality of what is out there. And yes, definitions and names do matter. Remember that none of these exoplanets orbit the Sun, so according to the IAU, none of them are planets at all.

  • B

    If the planetary data for HD 10180 is correct then the star system is significant. Not the gas giant planets themselves but their moons may be habitable. At least one of the giant planets
    probably have moons approximately the size of Mercury or Mars with a stable atmosphere.
    Because of the relatively close distance of planets to star such moons will likely have water in liquid and ice form. It would be proper to envision the moon with lakes of water and ice desert at the poles.


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