A New Planet Is Forming in an Earth-Like Orbit Around a Young Star

April 5, 2016 | Joanne Kennell

Proto-planetary disk
Photo credit: Sean Andrews/ALMA

Could this be an infant version of our home planet?

New images from the Atacama Large Millimeter/submillimeter Array (ALMA) have revealed never-before-seen details in the planet-forming disk around a nearby sun-like star. What is shows is disks of dust and gas — the formation sites of planets — at the same distance from the star as Earth is from the sun. This structure may mean there is an infant version of our home planet, or possibly a “super-Earth” beginning to form there.

Other features such as this are located 3 and 6 billion kilometers from the central star, similar to the distances from the sun to Uranus and Pluto in our own solar system.

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The star, TW Hydrae, is often studied by astronomers because of its proximity to Earth and its status. It is approximately 175 light-years away and is just 10 million years old. This gives astronomers a rare, undistorted view of the complete disk.

“Previous studies with optical and radio telescopes confirm that this star hosts a prominent disk with features that strongly suggest planets are beginning to coalesce,” Sean Andrews with the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and lead author on the paper published in Astrophysical Journal Letters, explained in a press release.

“The new ALMA images show the disk in unprecedented detail, revealing a series of concentric dusty bright rings and dark gaps, including intriguing features that suggest a planet with an Earth-like orbit is forming there,” Andrews continued.

To develop the image, astronomers used faint radio emissions from millimeter-size dust grains in the disk, revealing details on the order of one astronomical unit, which is about 150 million kilometers (93 million miles), or the distance between the Earth and the sun. “This is the highest spatial resolution image ever of a protoplanetary disk from ALMA, and that won't be easily beaten going forward,” said Andrews in the release.

“TW Hydrae is quite special. It is the nearest known protoplanetary disk to Earth and it may closely resemble our Solar System when it was only 10 million years old,” co-author David Wilner, also with the Harvard-Smithsonian Center for Astrophysics, said in the press release.

Earlier ALMA observations of another system, HL Tau with a younger protoplanetary disk just one million years old, can display similar signatures of planet formation. By studying the older TW Hydrae disk, as well as earlier ALMA observations of another system, HL Tau, a younger protoplanetary disk just one million years old, astronomers hope to better understand the evolution of our own planet.

The astronomers next phase of research is to investigate how common these kinds of features are in disks around other young stars, and how they change with time and their environment.

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