A massive new planet, nine times the size of Jupiter, is being formed in an intense and violent process, as recorded by NASA’s Hubble space telescope, challenging understandings about planetary formation.
Called AB Aurigae b, the planet is embedded in a disc of gas and dust spiraling around a young star that is about 2 million years old, according to estimates published in the journal Nature Astronomy. The star is of the age when our own solar system’s formation was underway, about 4.6 billion years ago.
“Nature is clever; it can produce planets in a range of different ways,” said Thayne Currie of the Subaru Telescope, who led the research appearing in Nature. “We could not detect this motion on the order of a year or two years,” Currie said. He added, “Hubble provided a time baseline, combined with Subaru data, of 13 years, which was sufficient to be able to detect orbital motion.”
Hubble’s resolution and length of time in space has provided clear photographic evidence of how large planets such as Jupiter are formed.
All planets are believed to be composed of material originating in a disc swirling around a central star in a process known as core accretion. This theory holds that planets embedded in such a disc grow gradually from objects ranging in size from grains of dust to boulders that collide and adhere together in orbit. A resulting core then pulls in gases from the disc.
(Subaru Telescope, Eureka Scientific Inc./Newsflash)
Huge planets such as Jupiter, which feature swirling gases have long sparked debate that challenged the dominant theory about planet formation. The disc instability theory contends that as a massive disc cools down around a central star within a swirling disc, gravity causes the disc to break into fragments that become planets.
AB Aurigae is about nine times bigger than Jupiter, which in turn is 1,300 times bigger than Earth. The nascent planet orbits its star approximately 8.6 billion miles away, or about twice the distance Pluto ranges from our Sun.
Over such distances, the astronomers believe, planets of Jupiter’s size might not ever develop by core accretion. Therefore, they concluded that disc instability formed the growing proto-planet at such a great distance from the star it orbits.
While Currie was initially skeptical that AB Aurigae was indeed a planet, images taken by the Subaru Telescope in Hawaii, when combined with archival data provided by Hubble, were decisive in leading him to his ultimate conclusions. “We could not detect this motion on the order of a year or two years,” Currie said.
He added, “Hubble provided a time baseline, combined with Subaru data, of 13 years, which was sufficient to be able to detect orbital motion.”
Co-author Olivier Guyon of the University of Arizona said, “AB Aurigae b has now been looked at in multiple wavelengths, and a consistent picture has emerged – one that’s very solid.”
“This new discovery is strong evidence that some gas giant planets can form by the disk instability mechanism,” said Alan Boss of the Carnegie Institution of Science. “In the end, gravity is all that counts, as the leftovers of the star-formation process will end up being pulled together by gravity to form planets, one way or the other,” he continued. While he was not directly involved in the published study, Boss is the author of a 1998 paper that was cited by the new study.
Future studies of AB Aurigae and similar planet-producing discs may reveal their chemical composition by using Hubble and Subaru, as well as NASA’s James Webb Space Telescope.
AB Aurigae is located in the Auriga constellation and is about 531 light years from the Sun. It has a mass about 2.4 times that of the Sun, and is radiating 38 times our star’s luminosity.
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Story By: Martin M Barillas, Sub-Editor: William McGee, Agency: Newsflash
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