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Another Solar System Like our Own?

Artists impression shows the planetary system around the Sun-like star HD 10180. Credit: ESO/L. Calçada

There is another Sun-like star out there with an intriguing family of planets orbiting about and it could be the closest parallel to our own solar system that astronomers have found yet. European astronomers discovered a planetary system containing at least five planets, orbiting the star HD 10180, with evidence that two other planets may be present. If confirmed, one of those would have the lowest mass ever found.

“We have found what is most likely the system with the most planets yet discovered,” says Christophe Lovis, who led the team. “This remarkable discovery also highlights the fact that we are now entering a new era in exoplanet research: the study of complex planetary systems and not just of individual planets. Studies of planetary motions in the new system reveal complex gravitational interactions between the planets and give us insights into the long-term evolution of the system.”

To make this system even more intriguing, the team also found evidence that the distances of the planets from their star follow a regular pattern, as also seen in our Solar System. “This could be a signature of the formation process of these planetary systems,” said team member Michel Mayor.

HD 10180, is located 127 light years away in the southern constellation of Hydrus. The five confirmed planets are large, about the size of Neptune — between 13 and 25 Earth masses —with orbital periods ranging from between six and 600 days. The planets’ distances from the star ranges from 0.06 and 1.4 times the Earth–Sun distance.

A close-up of the sky around the star HD 10180. Credit: ESO and Digitized Sky Survey 2. Acknowledgment: Davide De Martin

“We also have good reasons to believe that two other planets are present,” said Lovis. One would be a Saturn-like planet (with a minimum mass of 65 Earth masses) orbiting in 2200 days. The other would be the least massive exoplanet ever discovered, with a mass of about 1.4 times that of the Earth. It is very close to its host star, at just 2 percent of the Earth–Sun distance. One “year” on this planet would last only 1.18 Earth-days.

“This object causes a wobble of its star of only about 3 km/hour— slower than walking speed — and this motion is very hard to measure,” says team member Damien Ségransan. If confirmed, this object would be another example of a hot rocky planet, similar to Corot-7b.

The team used the planet-finding HARPS spectrograph, attached to ESO’s 3.6-metre telescope at La Silla, Chile, and made observations of HD 10180 for six years.

The newly discovered system of planets around HD 10180 is unique in several respects. First of all, with at least five Neptune-like planets lying within a distance equivalent to the orbit of Mars, this system is more populated than our Solar System in its inner region, and has many more massive planets there. Furthermore, the system probably has no Jupiter-like gas giant. In addition, all the planets seem to have almost circular orbits.

With this new announcement, the total number of exoplanets found is 472.

The team’s paper was submitted to Astronomy and Astrophysics (“The HARPS search for southern extra-solar planets. XXVII. Up to seven planets orbiting HD 10180: probing the architecture of low-mass planetary systems” by C. Lovis et al.).

Source: ESO

About 

Nancy Atkinson is Universe Today's Senior Editor. She also works with Astronomy Cast, and is a NASA/JPL Solar System Ambassador.

Comments on this entry are closed.

  • pink August 24, 2010, 7:36 AM

    Awesome…!!!

    This is really inspiring.

  • Spoodle58 August 24, 2010, 8:43 AM

    This is what its all about fellow astronomers, it doesn’t get much better than this.
    Great time to be around.

  • Torbjorn Larsson OM August 24, 2010, 10:15 AM

    When the Kepler results filled in the gaps and showed that our solar isn’t as unique, I was happy with the 5 planet system then most numerous. Now I’m even happier.

    Ob nitpicks/Q:
    – “the least massive exoplanet” – an hypothesis rejected by several pulsar exoplanets. Maybe they should contextualize the non-pulsar population and call the outgroup the “exoexoplanets”?

    – “unique in several respects … no Jupiter-like gas giant”. Surely Neptune analogue largest have been found before!? (And here it’s an Saturn analogue largest.)

    the team also found evidence that the distances of the planets from their star follow a regular pattern, as also seen in our Solar System.

    More fundamentally they see an extension of the earlier found “dynamically packed” gas giant distribution to low-mass systems – one can’t often plunk a planet down between those found and retain stability – “planets group as close as they can: no gaps allowed”. Ooh, nice!

    Ob bitching: Their subsequent pattern seeking attempt may be fruitful, but they need more data and better analysis in this layman’s opinion. I’m reminded of Cosma Shalizi’s paper on how most “power laws” aren’t. When you actually construct a test instead of rely on curve fitting, exponentials will be found to fit most anything of the sort better and reject the power law models.

  • TerryG August 24, 2010, 11:29 AM

    Very exciting times spoodle58, meanwhile NASA is due to make an announcement on Thursday about progress with the Kepler exoplanet mission. Lets hope it’s more than a routine update.

  • Lawrence B. Crowell August 24, 2010, 2:15 PM

    This is a strange stellar system in fact. It is only similar to the solar system in that it probably has terrestrial planets, in fact maybe many of them. Some of these Neptune bodies could have terrestrial moons, some might be like Earth.

    Outside that that, this stellar system is very different! There are five Neptune-like planets within .06-1.4AU. That is a lot of gravitational dynamics, and the article says the orbits are in nonresonant conditions. In some sense they would have to be, for resonance at these strong limits (close orbits and fairly large masses) would result in the denominator instability problem. So there is something funny going on with the dynamics here, which is counter intuitive.

    The prospects for life may not be that good IMO. In looking at the encyclopedia

    http://exoplanet.eu/catalog-all.php

    it is clear most of these Neptunians are very hot, while the outer one is nearly at the Martian orbital radius. A freely orbiting terrestrial might exist at about 1AU, if the dynamics are stable.

    On balance I would say this stellar system is remarkably different from our solar system.

    LC

  • Nexus August 24, 2010, 8:36 PM

    “A freely orbiting terrestrial might exist at about 1AU, if the dynamics are stable.”

    Imagine standing on the surface of it and looking at the night sky.

  • Torbjorn Larsson OM August 24, 2010, 10:36 PM

    This field moves fast! What was actually accepted as candidates (@ the link Lawrence provided) were the 6 first signals. Probably because “We thus conclude that a planetary origin is the only viable interpretation for the first 6 RV signals” in the paper.

    And now we have 485 exoplanet candidates…

  • Lawrence B. Crowell August 25, 2010, 4:01 AM

    This system has sparked some discussion between myself and somebody I know who is a classical mechanics guru, B. Jefferys from UTA. I find it interesting that this system can remain stable over the long period of time these star has existed. The Lyapunov exponents for chaotic behavior are likely to be fairly large.

    Maybe a terrestrial planet exists at around 1AU could be stable. It is possible that the nonresonant condition between these Neptunians is such that a terrestrial planet in some orbit could have a near resonant condition with the planets at 122 and 601 day period orbits. A terrestrial planet around the 601 day orbit Neptunian might harbor life. The conditions might be a bit on the cold side though.

    If you stood on such a planet the morning and evening might be pretty spectacular, with the 122 day period Neptunian being very bright. I don’t know how visible the planets closer to the star would appear.

    This star is at 40 Pc, which is close to the range of stars we might be able to send a probe to.

    LC

  • Spoodle58 August 25, 2010, 9:27 AM

    It seems that we come across systems that we may not have thought about before, I doubt anyone was waiting for a system that had 5 Neptune mass planets inside 1.4AU.

    I suppose if we saw our system from afar, all we would see with current tech (kepler not included) would be the four gas planets.

    Earth like moons in orbit around these would be most interesting. This is fun.

  • jimhenson August 25, 2010, 7:57 PM

    All 5 Neptune sized planets could each have dozens of terrestial like rocky surface satellite moons that would be within the comfort zone for liquid water to exist and support life.

  • Vance_D August 25, 2010, 2:51 PM

    Could you help me understand why HD 10180 not’s list Planet Quest, or NStED sites? Thank you…

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