S. Charpinet
Artist's rendering of the two alien planet candidates KOI 55.01 and KOI 55.02, which apparently survived their star's red-giant phase. They now circle close to the star's core.
updated 12/21/2011 3:21:06 PM ET 2011-12-21T20:21:06

Astronomers have discovered two potential alien planets that apparently survived being engulfed by their bloated, dying parent star.

The discovery is a surprise to many scientists, as it had been widely believed that no planet could withstand such a thorough and intense scorching, researchers say. Also a surprise: The hardy alien worlds seem to have inflicted their own damage on the expanded star, stripping it of much of its mass.

"To our knowledge, there has been no previous case reported where such a strong influence on the evolution of a star seems to have occurred," said study lead author Stephane Charpinet of the University of Toulouse in France.

Studying a dying star's light
Charpinet and his colleagues made the find using NASA's planet-hunting Kepler space telescope, which recently discovered the first two Earth-size worlds beyond our solar system.

For the new study, detailed in Thursday's edition of the journal Nature, the researchers didn't set out looking for alien planets. Instead, they were studying a dying star called KIC 05807616. The star was once a "normal" main-sequence one like our own sun, but it's now several steps farther down the path of stellar evolution.

For instance, KIC 05807616 has already gone through its red-giant phase, bloating up dramatically after exhausting the stores of hydrogen fuel in its core. The star has since collapsed to a shrunken vestige of its former self, becoming what's known as a hot B subdwarf.

While studying KIC 05807616's light, Charpinet and his team noticed periodic brightness variations recurring every 5.8 and 8.2 hours. They determined that these variations were caused by two small planets zipping around the star in extremely close orbits.

Kepler normally detects planets by what's known as the "transit method," flagging the tiny brightness dips caused when a planet crosses in front of — or transits — a star's face, blocking some of its light.

But in this case, the researchers concluded that they weren't seeing dimming caused by planetary transits. Instead, Kepler was flagging light that the planets themselves were reflecting and emitting.

"Light that is directly emitted or reflected from extrasolar planets has been detected in the past, but this is the first time that this particular method has been used for the discovery of a planetary system," astronomer Eliza Kempton of the University of California at Santa Cruz wrote in an accompanying essay in the same issue of Nature.

The two newfound planet candidates, known as KOI 55.01 and KOI 55.02, still need to be confirmed by follow-up observations. Both appear to be slightly smaller than Earth, but they hug their host star much more closely than our planet does.

  1. Space news from NBCNews.com
    1. KARE
      Teen's space mission fueled by social media

      Science editor Alan Boyle's blog: "Astronaut Abby" is at the controls of a social-media machine that is launching the 15-year-old from Minnesota to Kazakhstan this month for the liftoff of the International Space Station's next crew.

    2. Buzz Aldrin's vision for journey to Mars
    3. Giant black hole may be cooking up meals
    4. Watch a 'ring of fire' solar eclipse online

Both orbit at less than 1 percent of the Earth-sun distance (which is about 93 million miles, or 150 million kilometers), researchers said, so both planets are almost certainly far too hot to support life as we know it.

Destroyed gas giants
The two potential exoplanets likely didn't start out so small and so close-in, researchers said. Before KIC 05807616 became a red giant, both alien worlds were probably Jupiterlike gas giants sitting farther away from the star.

But then KIC 05807616's stellar envelope bloated immensely, engulfing the two planets. This seems to have had serious consequences for both the star and the alien worlds, researchers said.

"As the star puffs up and engulfs the planet, the planet has to plow through the star's hot atmosphere and that causes friction, sending it spiraling toward the star," study co-author Betsy Green of the University of Arizona said in a statement. "As it's doing that, it helps strip atmosphere off the star. At the same time, the friction with the star's envelope also strips the gaseous and liquid layers off the planet, leaving behind only some part of the solid core, scorched but still there."

These dramatic events could shed light on the evolution and ultimate fate of planetary systems, researchers said. Astronomers know of many systems with close-in giant planets, and some of them could eventually go down a similar road, leaving behind burnt-out planetary cores and a shrunken dwarf star.

Our own solar system will probably take a slightly different path, however. Our sun will become a red giant in about 5 billion years, likely expanding to engulf and thoroughly cook Mercury, Venus and Earth. But the sun will feel no reprisals, for these planets are too small to take a piece out of our star in the process, Charpinet said.

"It likely takes the engulfment of sufficiently massive giant planets comparable to Jupiter to influence the evolution of a star," Charpinet told Space.com in an email. "Our sun has giant planets, but they are probably too far away from it to be caught in the expanding star envelope during the red-giant phase."

You can follow Space.com senior writer Mike Wall on Twitter:@michaeldwall. Follow Space.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.

© 2013 Space.com. All rights reserved. More from Space.com.

Video: New frontiers in space

Photos: Month in Space: January 2014

loading photos...
  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
  1. Editor's note:
    This image contains graphic content that some viewers may find disturbing.

    Click to view the image, or use the buttons above to navigate away.

  2. Editor's note:
    This image contains graphic content that some viewers may find disturbing.

    Click to view the image, or use the buttons above to navigate away.

  3. Editor's note:
    This image contains graphic content that some viewers may find disturbing.

    Click to view the image, or use the buttons above to navigate away.

  4. Editor's note:
    This image contains graphic content that some viewers may find disturbing.

    Click to view the image, or use the buttons above to navigate away.

Interactive: The search for extrasolar planets


Discussion comments


Most active discussions

  1. votes comments
  2. votes comments
  3. votes comments
  4. votes comments