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Astronomers using the powerful exoplanet imaging system at Subaru Telescope on Mauna Kea have revealed the first-ever look at the earliest stages of the formation of a Jupiter-like planet in a distant solar system.
The emerging planet’s location and surrounding patterns of matter in the dust and gas disk surrounding star AB Aurigae also suggest an alternative method of planet formation unlike the one thought to have been at work in our own solar system.
The findings are found in a scientific paper published this week in the journal Nature Astronomy.
When lead author Thayne Currie first made the detection in 2016, he didn’t quite believe it was a newly forming planet. So he sat on the discovery and waited for additional data for confirmation.
“It required a lot of patience,” Currie said.
Over time, with the quality of observations increasing, it became clear that it was indeed a rarely seen protoplanet, or newly forming planet. In 2020, he said, he could almost see the new planet without having to fill in the data gaps with additional calculations.
Meanwhile, two other astronomy teams, one in Arizona and the other in Chile, published papers about the disk around AB Aurigae. But they were unable to report the existence of the protoplanet.
Currie, a Subaru astronomer who also works for the NASA-Ames Research Center, credited the superior viewing conditions atop Mauna Kea and the state-of-the-art technology and staff support at the Subaru Telescope for allowing the discovery to happen.
Subaru’s extreme adaptive optics instrument, SCExAO, allows for sharper images as it eliminates the turbulence in our atmosphere while blocking out the starlight. The scientists also used images from the Hubble Space Telescope.
“One of SCExAO’s strengths is that it continues to evolve over the years to meet the needs of our observers. We were able to confirm this discovery thanks to recent upgrades to our instrument,” SCExAO scientist and co-author Julien Lozi said in a release.
Published Monday in the paper by Currie and an international group of 32 co- authors, the discovery could help to explain the histories and features of extrasolar planets seen around other stars and offers an alternative to the standard model of planet formation.
In the standard model, a large Jupiter-like gas planet starts as a rocky core in a disk around a young star. This core then gathers gas from the disk as it grows into a giant planet.
While this model fits with the creation of the planets in our neighborhood, it doesn’t exactly explain all the exoplanets that have been discovered at distances farther away from their stars. Many of them orbit their stars at distances greater than our solar system’s outermost planet, Neptune, orbits the sun.
That is the case for newly discovered protoplanet AB Aur b, which sits at a distance from AB Aurigae three times the distance between the sun and Neptune.
Nearby spiral structures in the disk match a planet- formation model in which the planet forms directly from the gravitational collapse of the surrounding matter, according to the paper.
Currie said this “disk instability” theory was proposed in the ’50s and ’60s but later discarded following more research into the formation of gas giants like Jupiter and Saturn. The evidence, he said, now suggests this model is once again a viable alternative to the standard model of planet formation.
The latest discovery is only the second protoplanet identified by astronomers and the youngest in its stages of development. The infant star AB Aurigae is only a few million years old, and the emerging protoplanet may be only a few thousand years old.