Telescope sees 'baby planet' forming around distant star

Astronomers using European Southern Observatory's Very Large Telescope (VLT) have captured the birth of a planet around a star 520 light-years away.

The image might not look like much at first glance. But among the swirling clouds of dust and gas is a little twist. That twist, astronomers hypothesize, is evidence of a planet forming as it rotates around its star.

The parent star of the developing planet is AB Aurigae, found in the constellation Auriga, a familiar constellation in the Northern Hemisphere. It is about one to five million years old, far younger than our 4.5 billion-year-old sun, and roughly four times more massive.

The spiral arms around the star were first detected five years ago using ESO's Atacama Large Millimeter Array telescope in Chile, but it wasn't able to observe this much detail. Using a special instrument on the VLT called SPHERE, astronomers were able to block out the star's bright light and conduct extremely precise observations.

These types of spirals around young stars are indicative of newly forming planets and are created as these planets give the gas a "kick," which in turn creates a disturbance of the swirling disc and forms a wave. The twists observed are in a kind of s-shape as gas swirls around the planet.

We do not see the planet yet, but we do see the material that is forming the planet, and we do see the mechanism at play for the formation of the planet.- Emmanuel Di Folco, astronomer and paper's co-author

"These twists must be produced by a baby planet, which we don't see directly, but we see the influence of the planet onto the spiral," said Emmanuel Di Folco, co-author of the paper published in the journal Astronomy & Astrophysics and an astronomer at the Astrophysics Laboratory of Bordeaux in Bordeaux, France.

"We do not see the planet yet, but we do see the material that is forming the planet, and we do see the mechanism at play for the formation of the planet. And this was very exciting because the structure — the shape of this structure that we have detected — was exactly the shape that was predicted by theoretical models of planet formation."

Astronomers hypothesize that stars and planets form after they're given a different sort of kick, perhaps by a relatively nearby supernova explosion. Gas and dust first form the star and what remains forms the planets.

Origin story

While more than 4,000 exoplanets — planets orbiting a distant star — have been discovered, it's rare to see one so early on in its formation.

And Di Folco said that it's likely this planet might have some company.

"In the [below] image on the right-hand panel there is a small red dot, which we believe is also a planet, and what you're really seeing is that this planet is at the outer edge of what we call a cavity in this disc," Di Folco said. 

The cavity is a region where there is much less gas and dust, potentially created by another planet. It's similar to the mechanism that creates gaps in Saturn's rings.

"There may be other planets somewhere hidden behind the structure that we see here that we will detect later on, but we cannot yet interpret all the structure of that we see."

The developing planet is roughly the same distance from its star as Neptune is from the sun, but it's not Earth-like.

"It's going to be a giant planet. It's not going to be a terrestrial planet," said Anthony Boccaletti, lead author and an astronomer at the Laboratory for Space Science and Astrophysical Instrumentation at the Paris Observatory in Meudon, France. "It's really a massive one … probably something like Jupiter or even more massive than Jupiter."

'That would be amazing'

The image of this nascent planet is yet another step in better understanding how planetary systems form, including our own.

"This is part of our origin," said Di Folco. "Here we have a snapshot of what could have been the formation of Neptune or or Saturn or Jupiter — our giant planets in the solar system."

Di Folco said that they hope to conduct further observations, perhaps even capturing the suspected other planets in the system. But he's also hoping that in the not-too-distant future, astronomers will be able to capture an image of an even younger planet.

"We are coming into a new era in astronomy where we'll be able really to see — in a few years or maybe even 10 years from now — the direct formation of those planets around young stars," Di Folco said.

"That would be amazing."