Now we knew that planets had to have a formation period. We’ve even seen some titillating hints of planets forming around the time of planet formation. But now we’ve caught them in the act. For the first time, researchers have photographed the birth of a distant planet. Of course planets take several millions years to form, so we can only ever capture stills, but we can use a simulation in this video.
We know of about 2,000 exoplanets, but we’ve only imaged about a dozen, and all of them well beyond their baby phase. This new data, published in the journal Nature this week, provides our first real peek at the birth phase. The LkCa15 system was observed using Arizona’s Large Binocular Telescope, the world’s largest telescope, and the University of Arizona’s Magellan Telescope, found in Chile. The Magellan Telescope has a special adaptive optics system that was able to pick up the planet’s “hydrogen alpha” light — a specific red wavelength of light that stars and planets emit as they grow. These cosmic objects get really hot when they form, causing their hydrogen components to glow this deep red that can be observed from Earth.
This embryonic exoplanet orbits a young star called LkCa15, only about 450 light years from Earth. Surrounding LkCa15 is a huge, protoplanetary disk — a rotating saucer of dense gas that typically encompasses young stars. Within these disks planets form when some of the materials coalesce into larger objects. This creates gaps in the dust cloud where the new planets then reside. The protoplanetary disk around LkCa15 is unique – it contains an exceptionally large gap.
“It’s like a big doughnut,” said study author Kate Follette. “This system is special because it’s one of a handful of disks that has a solar-system size gap in it. And one of the ways to create that gap is to have planets forming in there.” She was able to separate the hydrogen alpha light coming from the star, to get the image of the emerging exoplanet. But, as always we couldn’t see everything — and they think there may be still more planets forming while we watch.