Hubble: Giant Stellar Debris Disk Reveals a Violent Planet Nursery

New Hubble images have revealed an exploded field of dust around young star HR 4796A that could be debris from colliding infant planets in an evolving exoplanetary system.   

Intense light from the eight-million-year-old star forced the huge dusty swath out across billions of miles of space from a previously known bright inner ring, researchers suggest in a study recently published in the Astronomical Journal.

Field of dust scattered by starlight

3_7_Stellar Dust System A huge complex dust system surrounds young star HR 4796A. G Schneider/University of Arizona/ESA/NASA

This inner ring of debris shines seven billion miles from the star. Astronomers think it may be have been gathered together by the gravitational force of a huge unseen planet nearby.

The Hubble images reveal the ring is surrounded by a mysterious field of dust exploding in all directions. It stretches an enormous 150 billion miles across. This dust, researchers think, has been expelled by starlight from HR 4796A, which is 23 times brighter than the sun. 

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The dynamics of the system get even weirder. The catapulted dust is skewed in one direction. Researchers think this could be caused by the host star careering through the field, creating waves in the dust like a boat through water. Or the young star’s binary partner, HR 4796B, might be tugging at the debris.

"The dust distribution is a telltale sign of how dynamically interactive the inner system containing the ring is," said Glenn Schneider of the University of Arizona, Tucson, in a statement. Schneider, one of the study authors, used Hubble's Space Telescope Imaging Spectrograph to investigate the small dust particles enveloping HR 4796A. He added: “The gross asymmetries of the outer dust field are telling us there are a lot of forces in play (beyond just host-star radiation pressure) that are moving the material around. We've seen effects like this in a few other systems, but here's a case where we see a bunch of things going on at once."

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Dusty disks are thought to be common around stars, with some 40 imaged so far. Probing them sheds light on the mysterious dynamics of systems in the throes of planetary formation.

"We cannot treat exoplanetary debris systems as simply being in isolation," Schneider explained. "Environmental effects, such as interactions with the interstellar medium and forces due to stellar companions, may have long-term implications for the evolution of such systems.” 

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