Photograph catches planet within the act of forming

Photographic evidence of the new planet forming.

Co-author of the paper, Professor Tuthill, said the images provided unambiguous evidence.

Astronomers led by Stephanie Sallum at the University of Arizona and Katherine Follette at Stanford University have discovered the first planet to be studied while still in the process of formation. “Fortunately, our solar system had nothing as massive as these planets as their gravity would have kicked smaller Earth-sized planets out into the depths of space”.

Because LkCa 15 is so far away, the span between the star and its planets appears mind-bogglingly close to Earth-based telescopes, like the width of a pin from a kilometer (0.62 miles) away.

“The researchers’ discovery provides stringent constraints on planet-formation theories”, Zhaohuan Zhu of Princeton University, who was not affiliated with the new study, wrote in an accompanying “News & Views” piece in the same issue of Nature.

The still-forming planet was spotted in a gap in the protoplanetary disk of LkCa15, a star 450 light-years from Earth.

For years, astrophysicists have been targeting star systems that are halfway between an infant and mature stars – and which may host a family of fully formed planets. The central clearings within transition disks are believed to be created by the formation of planets, which sweep up dust and gas from the disk as they orbit the star.

To learn more, Sallum and her colleagues zeroed in on the LkCA 15 system using the Large Binocular Telescope (LBT), an observatory in southeastern Arizona that boasts two 27-foot-wide (8.4 meters) primary mirrors. The protoplanet is very close to its parent star, Follette said, and if it were much closer or fainter, Lk Ca 15 would have washed out its light completely.

Capturing sharp images of distant objects was challenging, in large part because of atmospheric turbulence, said Professor Laird Close, Dr Follette’s graduate adviser. “That’s because of researchers at the University of Arizona who have developed the instruments and techniques that make that hard observation possible”, she says.

While we don’t have real life images just yet, the illustrations that you are about to see are something really special. The researchers overlaid infrared images of the LkCa-15 star system taken by the Large Binocular Telescope in Arizona with a highly specific measurement of a certain wavelength of red light-called hydrogen-alpha emissions-from the Magellan Telescopes in Chile.

One of the key questions raised by the emerging LkCa 15 system is how such a giant planet can form and still be growing around a star that is just 2 million years old.

When cosmic objects are forming, they get extremely hot, and because they are forming from hydrogen, those objects all glow a deep red, which astronomers refer to as H-alpha, a particular wavelength of light. Mature planets can be detected when they pass in front of the stars they orbit, causing their light to dim. In that time, they used a technique called hydrogen-alpha detection. “We were able to separate the light of the faint planet from the light of the much brighter star and to see that they were both growing and glowing in this very distinct shade of red”.