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Extreme Solar Systems: Why Aren’t We Finding Other Planetary Systems Like Our Own?

Artist concept of a previous multi-planet solar system found by the Kepler spacecraft. Credit: NASA/Tim Pyle

Most planetary systems found by astronomers so far are quite different than our own. Many have giant planets whizzing around in a compact configuration, very close to their star. An extreme case in point is a newly found solar system that was announced on October 15, 2012 which packs five — count ‘em — five planets into a region less than one-twelve the size of Earth’s orbit!

“This is an extreme example of a compact solar system,” said researcher Darin Ragozzine from the University of Florida, speaking at a press conference at the American Astronomical Society’s Division for Planetary Sciences meeting. “If we can understand this one, hopefully we can understand how these types of systems form and why most known planetary systems appear different from our own solar system.”

This new system, currently named KOI-500, was found with data from the Kepler planet-finding spacecraft, and Ragozzine said astronomers have now uncovered a new realm of exo-planetary systems.

“The real exciting thing is that Kepler has found hundreds of stars with multiple transiting planets,” he said. “These are the most information-rich systems, as they can tell you not only about the planets, but also the architecture of how solar systems are put together.”

The fact that almost all solar systems found so far are vastly different than our own has astronomers wondering if we are, in fact, the oddballs. A study from 2010 concluded that only about 10 – 15 percent of stars in the Universe host systems of planets like our own, with terrestrial planets nearer the star and several gas giant planets in the outer part of the solar system.

Part of the reason our dataset of exoplanets is skewed with planets that are close to the star is because currently, that is all we are capable of detecting.

But the surprising new population of planetary systems discovered in the Kepler data that contain several planets packed in a tiny space around their host stars does give credence to the thinking that our solar system may be somewhat unique.

However, perhaps KOI-500 used to be more like our solar system.

“From the architecture of this planetary system, we infer that these planets did not form at their current locations,” Ragozzine said. “The planets were originally more spread out and have ‘migrated’ into the ultra-compact configuration we see today.”

There are several theories about the formation of the large planets in our outer solar system which involves the planets moving and migrating inward and outward during the formation process. But why didn’t the inner planets, including Earth, move in closer, too?

“We don’t know why this didn’t happen in our solar system,” Ragozzine said, but added that KOI-500 will “become a touchstone for future theories that will attempt to describe how compact planetary systems form. Learning about these systems will inspire a new generation of theories to explain why our solar system turned out so differently.”

A few notes of interest about KOI-500:

The five planets have “years” that are only 1.0, 3.1, 4.6, 7.1, and 9.5 days.

“All five planets zip around their star within a region 150 times smaller in area than the Earth’s orbit, despite containing more material than several Earths (the planets range from 1.3 to 2.6 times the size of the Earth). At this rate, you could easily pack in 10 more planets, and they would still all fit comfortably inside the Earth’s orbit,” Ragozzine noted. KOI-500 is approximately 1,100 light-years away in the constellation Lyra, the harp.

Four of the planets orbiting KOI-500 follow synchronized orbits around their host star in a completely unique way — no other known system contains a similar configuration. Work by Ragozzine and his colleagues suggests that planetary migration helped to synchronize the planets.

“KOI” stands for Kepler Object of Interest, and Ragozzine’s findings on this system have not yet been published, and so the system has yet to officially be considered a confirmed planetary system. “Every time we find something like this we give it a license-plate-like number starting with KOI,” Ragozzine said.

When does a KOI become an official planet? Ragozzine said the process is by confirming and validating the data. “Basically you need to prove statistically or by getting a specific measurement that it is not some other astronomical signal,” he said.

This infographic from Space.com supplies more visual details:

Find out about the crowded KOI-500 alien solar system, in this SPACE.com infographic.

Sources: AAS, University of Florida

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.

  • Tim Amato October 16, 2012, 5:22 AM

    There are a few things, the spin rate and the composition of the materials in the solar system that would determine where materials accumulated. Also when were these materials, objects, planets aquired in the origin of the solar system when forming in the same area of space. What else was going on. Every place has its own combination; Lets be happy with what we have. It’s exciting to think there could be multiple planets in the same habital zone.

  • Extrasolar October 16, 2012, 8:05 AM

    KOI 500 has been on the known planet candidate list since February 2011. It’s discovery is nothing new.

  • zetetic elench October 16, 2012, 2:14 PM

    planets with long orbital periods will take a very long time to find. they also have a much lesser influence on the host sun’s radial velocity. both properties conspire.

  • BrianM October 16, 2012, 6:56 PM

    It’s because we are unique. There is no other life in the Universe. God created the earth and the heavens. He would of told us if there was another earth. But I know I’m a “religious wacko” so go ahead and bash me.

  • katesisco October 16, 2012, 6:56 PM

    Reading Miles Mathis last night THE MAJORANA FERMION which doesn’t exist but that photon-anti photons do. Spin cancellations will reduce the magnetic field to zero. In his paper on the MOON he points out gravitational fields vary as the radii vary. I think this is connected. As evidence by our sun’s north hemisphere collapse in J 2012 and the subsequent roaming of the Earth’s north pole which later was id’d on the sun’s surface also, I wonder if the collapse was a ZBP. So if the sun lost the north magnetic field in a ZBP the north magnetic field of the Earth was free to wander. Is this how polar wander happens? The sun field was rebuilt fairly quickly so regained magnetic control of E’s n magnetic pole.

    While in a ZBP state, the planetary bodies of a system would be free and respond to centrifugal force so perhaps the close in systems are the result of a solar ZBP?

    • Torbjörn Larsson October 16, 2012, 7:12 PM

      Nice mix of particles, different fields known to not mix at today’s energies (gravity vs magnetism), polar wander from planet to stars, and pseudoforce mechanics (centrifugal force). In short, take anything mystic for the layman, mix and serve.

      Oh, and nice touch with adding mysterious acronyms too. (O.o)

  • Torbjörn Larsson October 16, 2012, 7:08 PM

    Every system found is individual, more individual than planetary scientists expected. But the statistics is robust, and they predict many habitable Earth similar planets.

    The fact that almost all solar systems found so far are vastly different than our own has astronomers wondering if we are, in fact, the oddballs.

    They used to say the same when we could only detect large, close to the star planets. That changed somewhat as the detectabl planetary mass went down and orbital period went up, and it can be expected to change even more in the future.

    The same here. This system is densely packed, but we have already seen some systems with planets far from the star. Kepler needs to have a go at the planets in between.

    That is some years more worth of data. They need 7 year in total IIRC to get out to Earth orbit. And ideally a longer follow up mission that makes it out to Jupiter distances or so.

    There are several theories about the formation of the large planets in our outer solar system which involves the planets moving and migrating inward and outward during the formation process. But why didn’t the inner planets, including Earth, move in closer, too?

    I haven’t dug into the details, but very simplistic aggregation models seems to predict systems akin to what we observe here.

    On the other hand, recent models implies the inner disk behaves differently from the outer:

    “If it proves consistent, then we may have reconciled planet formation theory with the water-poor Earth: Regions of low turbulence in the protoplanetary disk allow formation of water-poor terrestrial planets.

    Also interesting is the icy inner region, which could potentially provide a habitat for gas giants to evolve closer in to the star. This is particularly relevant in the context of “Hot Jupiters”, extrasolar gas giants discovered orbiting very close in to their stars.”

    Maybe the real question is, why we don’t have a “Hot Jupiter” ourselves.

  • I3VI5 October 17, 2012, 4:05 AM

    “Part of the reason our dataset of exoplanets is skewed with planets that are close to the star is because currently, that is all we are capable of detecting.”

    There’s the answer!

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