Hubble Finds a Planet Forming in an Unconventional Way | NASA

 Hubble Finds a Planet Forming in an Unconventional Way | NASA

NASA's Hubble Space Telescope has directly photographed evidence of a Jupiter-like protoplanet forming through what researchers describe as an "intense and violent process." This discovery supports a long-debated theory for how planets like Jupiter form, called "disk instability."

"Interpreting this system is extremely challenging. This is one of the reasons why we needed Hubble for this project—a clean image to better separate the light from the disk and any planet."

Thayne Currie, lead researcher on the study

The new world under construction is embedded in a protoplanetary disk of dust and gas with distinct spiral structure swirling around surrounding a young star that’s estimated to be around 2 million years old. That's about the age of our solar system when planet formation was underway. (The solar system's age is currently 4.6 billion years.)

"Nature is clever; it can produce planets in a range of different ways," said Thayne Currie of the Subaru Telescope and Eureka Scientific, lead researcher on the study.

All planets are made from material that originated in a circumstellar disk. The dominant theory for jovian planet formation is called "core accretion," a bottom-up approach where planets embedded in the disk grow from small objects—with sizes ranging from dust grains to boulders—colliding and sticking together as they orbit a star. This core then slowly accumulates gas from the disk. In contrast, the disk instability approach is a top-down model where as a massive disk around a star cools, gravity causes the disk to rapidly break up into one or more planet-mass fragments.

The newly forming planet, called AB Aurigae b, is probably about nine times more massive than Jupiter and orbits its host star at a whopping distance of 8.6 billion miles—over two times farther than Pluto is from our Sun. At that distance it would take a very long time, if ever, for a Jupiter-sized planet to form by core accretion. This leads researchers to conclude that the disk instability has enabled this planet to form at such a great distance. And, it is in a striking contrast to expectations of planet formation by the widely accepted core accretion model.

The new analysis combines data from two Hubble instruments: the Space Telescope Imaging Spectrograph and the Near Infrared Camera and Multi-Object Spectrograph. These data were compared to those from a state-of-the-art planet imaging instrument called SCExAO on Japan's 8.2-meter Subaru Telescope located at the summit of Mauna Kea, Hawaii. The wealth of data from space and ground-based telescopes proved critical, because distinguishing between infant planets and complex disk features unrelated to planets is very difficult.

The research team's results are published in the April 4 issue of Nature Astronomy: https://www.nature.com/natastron/

The Hubble Space Telescope is a project of international cooperation between NASA and European Space Agency (ESA). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, in Washington, D.C.

Credit: NASA/European Space Agency (ESA)

Image Credits: Science: NASA, ESA, Thayne Currie (Subaru Telescope, Eureka Scientific Inc.); Image Processing: Thayne Currie (Subaru Telescope, Eureka Scientific Inc.), Alyssa Pagan (STScI)

Illustration Credit: NASA, ESA, Joseph Olmsted (STScI)

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