updated 9/17/2010 6:12:28 PM ET 2010-09-17T22:12:28

A newfound alien solar system with planets the size of Saturn circling close to their star is helping astronomers learn how some giant worlds snuggle up to their stellar parents like moths to a flame.

NASA's Kepler space observatory recently confirmed the presence of the two Saturn-sized planets that orbit a star about 2,300 light-years away from Earth. A third, much smaller planet may also orbit the star, circling so close that one year on the alien world would last just 1.6 Earth days.

While the discovery of the Kepler-9 planetary system is a major find, it is also a starting point for astronomers to learn how the planet arrangement formed in the first place.

Scientists think these planets originated much farther from their parent star and gradually migrated inward over time. All three objects could fit inside the orbit of Mercury today.

"It's safe to say that they did migrate because they ended up in this very special set of orbits," said Alycia Weinberger, an astronomer in the department of terrestrial magnetism at the Carnegie Institution of Washington in Washington, D.C., when the planets were announced in late August."

"The likely candidate for how that migration happened is interaction between these planets and the original disk of material – the gas out of which they formed. It will now take some work to try to figure out exactly how that was likely to happen in this system," Weinberger said.

Timing planet paths
Understanding the process of planetary migration will help astronomers understand the initial conditions that led to the final configuration of the Kepler-9 system, and other planetary systems discovered in the future.

As a planetary system is being formed, "planets can change locations or migrate due to interactions with the raw materials with which they are built," Weinberger said.

A study led by Matthew Holman, associate director of the theoretical astrophysics division at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., determined that the two Saturn-sized planets, named Kepler-9b and Kepler-9c, have somewhat atypical orbits.

It takes Kepler-9b about 19.2 days to complete one orbit. The other Saturn-sized world, Kepler-9c, makes one orbit every 38.9 days, taking almost twice as long to complete the circuit.

"There is a near 2-to-1 orbital resonance, which means the planets have orbital periods in a 2-to-1 ratio," Holman told "At this configuration, we can see that they strongly interact and we can see large variations in the orbits of the planets."

What planetary migration tells us
Studying how planetary migration occurs, and how much a planet has moved, can tell researchers a lot about the history of how such worlds and their local solar system formed.

Kepler-9b and 9c were found to have a lot of gravitational interaction, and they are located so close to their parent star that their orbits would fit inside the orbit of Mercury in our own solar system, said Holman.

The two planets most likely migrated to their observed locations, said Weinberger, because being so close to the star would have made it extremely difficult to develop and survive in the first place.

Observations combined with theoretical work will then be able to pinpoint how far apart the planets originated, how long it took them to form and how long their migration lasted.

"Kepler was designed and built to answer fundamental questions," Weinberger said. "We want to know what types of planetary systems there are; what is common amongst the various systems; whether there are any special conditions that result in Earth-like planets; whether the whole system of planet formation is robust and common."

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Photos: Month in Space: January 2014

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  1. Southern stargazing

    Stars, galaxies and nebulas dot the skies over the European Southern Observatory's La Silla Paranal Observatory in Chile, in a picture released on Jan. 7. This image also shows three of the four movable units that feed light into the Very Large Telescope Interferometer, the world's most advanced optical instrument. Combining to form one larger telescope, they are greater than the sum of their parts: They reveal details that would otherwise be visible only through a telescope as large as the distance between them. (Y. Beletsky / ESO) Back to slideshow navigation
  2. A balloon's view

    Cameras captured the Grandville High School RoboDawgs' balloon floating through Earth's upper atmosphere during its ascent on Dec. 28, 2013. The Grandville RoboDawgs’ first winter balloon launch reached an estimated altitude of 130,000 feet, or about 25 miles, according to coaches Mike Evele and Doug Hepfer. It skyrocketed past the team’s previous 100,000-feet record set in June. The RoboDawgs started with just one robotics team in 1998, but they've grown to support more than 30 teams at public schools in Grandville, Mich. (Kyle Moroney / AP) Back to slideshow navigation
  3. Spacemen at work

    Russian cosmonauts Oleg Kotov, right, and Sergey Ryazanskiy perform maintenance on the International Space Station on Jan. 27. During the six-hour, eight-minute spacewalk, Kotov and Ryazanskiy completed the installation of a pair of high-fidelity cameras that experienced connectivity issues during a Dec. 27 spacewalk. The cosmonauts also retrieved scientific gear outside the station's Russian segment. (NASA) Back to slideshow navigation
  4. Special delivery

    The International Space Station's Canadian-built robotic arm moves toward Orbital Sciences Corp.'s Cygnus autonomous cargo craft as it approaches the station for a Jan. 12 delivery. The mountains below are the southwestern Alps. (NASA) Back to slideshow navigation
  5. Accidental art

    A piece of art? A time-lapse photo? A flickering light show? At first glance, this image looks nothing like the images we're used to seeing from the Hubble Space Telescope. But it's a genuine Hubble frame that was released on Jan. 27. Hubble's team suspects that the telescope's Fine Guidance System locked onto a bad guide star, potentially a double star or binary. This caused an error in the tracking system, resulting in a remarkable picture of brightly colored stellar streaks. The prominent red streaks are from stars in the globular cluster NGC 288. (NASA / ESA) Back to slideshow navigation
  6. Supersonic test flight

    A camera looking back over Virgin Galactic's SpaceShipTwo's fuselage shows the rocket burn with a Mojave Desert vista in the background during a test flight of the rocket plane on Jan. 10. Cameras were mounted on the exterior of SpaceShipTwo as well as its carrier airplane, WhiteKnightTwo, to monitor the rocket engine's performance. The test was aimed at setting the stage for honest-to-goodness flights into outer space later this year, and eventual commercial space tours.

    More about SpaceShipTwo on PhotoBlog (Virgin Galactic) Back to slideshow navigation
  7. Red lagoon

    The VLT Survey Telescope at the European Southern Observatory's Paranal Observatory in Chile captured this richly detailed new image of the Lagoon Nebula, released on Jan. 22. This giant cloud of gas and dust is creating intensely bright young stars, and is home to young stellar clusters. This image is a tiny part of just one of 11 public surveys of the sky now in progress using ESO telescopes. (ESO/VPHAS team) Back to slideshow navigation
  8. Fire on the mountain

    This image provided by NASA shows a satellite view of smoke from the Colby Fire, taken by the Multi-angle Imaging SpectroRadiometer aboard NASA's Terra spacecraft as it passed over Southern California on Jan. 16. The fire burned more than 1,863 acres and forced the evacuation of 3,700 people. (NASA via AP) Back to slideshow navigation
  9. Where stars are born

    An image captured by NASA's Spitzer Space Telescope shows the Orion Nebula, an immense stellar nursery some 1,500 light-years away. This false-color infrared view, released on Jan. 15, spans about 40 light-years across the region. The brightest portion of the nebula is centered on Orion's young, massive, hot stars, known as the Trapezium Cluster. But Spitzer also can detect stars still in the process of formation, seen here in red hues. (NASA / JPL-Caltech) Back to slideshow navigation
  10. Cygnus takes flight

    Orbital Sciences Corp.'s Antares rocket rises from NASA's Wallops Flight Facility on Wallops Island, Va, on Jan. 9. The rocket sent Orbital's Cygnus cargo capsule on its first official resupply mission to the International Space Station. (Chris Perry / NASA) Back to slideshow navigation
  11. A long, long time ago...

    This long-exposure picture from the Hubble Space Telescope, released Jan. 8, is the deepest image ever made of any cluster of galaxies. The cluster known as Abell 2744 appears in the foreground. It contains several hundred galaxies as they looked 3.5 billion years ago. Abell 2744 acts as a gravitational lens to warp space, brightening and magnifying images of nearly 3,000 distant background galaxies. The more distant galaxies appear as they did more than 12 billion years ago, not long after the Big Bang. (NASA / NASA via AFP - Getty Images) Back to slideshow navigation
  12. Frosty halo

    Sun dogs are bright spots that appear in the sky around the sun when light is refracted through ice crystals in the atmosphere. These sun dogs appeared on Jan. 5 amid brutally cold temperatures along Highway 83, north of Bismarck, N.D. The temperature was about 22 degrees below zero Fahrenheit, with a 50-below-zero wind chill.

    Slideshow: The Year in Space (Brian Peterson / The Bismarck Tribune via AP) Back to slideshow navigation
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