Extreme solar systems: Why aren't we finding other planetary systems like our own?

October 16, 2012 by Nancy Atkinson,
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 '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 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 is that Kepler has found hundreds of stars with multiple transiting ," 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 so 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 nearer the star and several gas giant planets in the outer part of the solar system.

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

This infographic from Space.com supplies more visual details

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 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 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.

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5 / 5 (4) Oct 16, 2012
what else could he say -- telescopes that have been looking for planetary transits would have to have been looking for about 4 - 5 years to confirm a planet orbiting a star with an orbit similiar to an earth year. we have only been doing this for what a year and a half.
5 / 5 (7) Oct 16, 2012
We have currently two ways of detecting planets:
1) The planet transits in front of the star
2) The planet is massive and thereby induces a wobble in the stars position

1) Is also more likely to be noticed if the star is massive. We just don't have the tech yet to reliably detect Earth sized planets in Earth sized orbits.

So we shouldn't be surprised that we haven't found any candidates. And we shouldn't therefore jump to conclusions based on data that does not support them.
4.2 / 5 (5) Oct 16, 2012

Detection of planets can also be achieved through direct imaging and gravitational lensing. Indeed several have been discovered using these techniques.
3.3 / 5 (19) Oct 16, 2012
So we shouldn't be surprised that we haven't found any candidates. And we shouldn't therefore jump to conclusions based on data that does not support them.
We can jump to the conclusion that competent researchers have already factored your caveats into their conclusion-jumping.

So. It appears that it is not enough for pseudogod aliens to seed systems with life - they must re-engineer them to enable it to thrive and evolve.

This includes placing potential planets for colonization and terraforming within reasonable reach of the motherworld, and leaving asteroids and comets in potential impact trajectories so as to compel emerging sentients to develop the means to do so before they are extincted by impacts.

Interesting. It is like a test, a rite of passage. Fly or die.
5 / 5 (4) Oct 16, 2012
We can jump to the conclusion that competent researchers have already factored your caveats into their conclusion-jumping.

Yes, that's true, and that's where they get the 10-15% estimate. I expect this estimate to get a major revision upwards in the next few years. Kepler is capable of detecting earth-like planets around sun-like stars, and Antialias is correct that there hasn't been enough time for Kepler to identify them yet. The Kepler mission is expected to discover a TON of earth-like planets within a 5 year timeframe, but we haven't reached that threshold yet. An earth-like planet would take more than 4 years to do enough transits for Kepler to pick it up. Currently we CAN eliminate a certain percentage of stars as not having an earth-like planet because we can see that they have jupiter sized planets in orbits that prevent an earth orbit. We can only currently assume a ratio of big to little planets based on loosely constrained theory. The error margin is wide.
not rated yet Oct 16, 2012

-- actually I was the one that said we haven't had enough time -- along with the scientist the article is quoting

antialias was just being a little troll
Shinobiwan Kenobi
1 / 5 (1) Oct 17, 2012

-- antialias was just being a little troll

Contributing related information to expand/assist in understanding the topic of discussion is trolling? <== This is trolling :P

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