Wham! Planetary Impact Detected in Faraway Star System

Astronomers have spotted the wreckage of a mammoth collision around a distant young star, a landmark find that could shed light on how our own solar system's rocky planets took shape long ago.

The researchers detected a huge disk of dusty debris around a sunlike star called NGC 2547-ID8, which lies about 1,140 light-years from Earth in the constellation Vega. The cloud was probably spawned when two planetary building blocks slammed into each other just two years earlier, scientists said.

"This is the first detection of a planetary impact outside of our own solar system," study lead author Huan Meng of the University of Arizona in Tucson told [Video: Moon Made by Giant Impact with Earth: New Evidence]

Image: Infrared chart
Astronomers were surprised to see these data from NASA's Spitzer Space Telescope in January 2013, showing a huge eruption of dust around a star called NGC 2547-ID8. In this plot, infrared brightness is represented on the vertical axis, and time on the horizontal axis. NASA / JPL-Caltech / Univ. of Ariz.

Further, NGC 2547-ID8 is the same mass and size as our sun, and it's just 35 million years old — the same age the sun was when similar impacts were building Earth, Mars and the other rocky planets.

"This discovery really puts our own solar system into context," Meng said.

Meng and his colleagues studied NGC 2547-ID8 using NASA's Spitzer Space Telescope and ground-based instruments. They watched the star from May 2012 to August 2013, with a hiatus from mid-August 2012 to January 2013 when the object was too close to the sun to be observed.

When NGC 2547-ID8 came back into view in January 2013, Spitzer registered a brief flare-up of infrared light, indicative of emission from small dust particles.

Computer modeling work suggested that the surge was caused by the impact of two big, rocky objects —large asteroids or protoplanets, the progenitors of full-fledged rocky worlds such as Earth, in the "terrestrial planet zone" of the NGC 2547-ID8 system.

The collision probably occurred during or slightly before the 2012-13 observing gap, Meng said. It generated a mammoth cloud of vapor that condensed into small silicate spherules, which were in turn broken down into dust by subsequent collisions among themselves.

These dust particles are so small that they were quickly expelled from the NGC 2547-ID8 system by stellar radiation pressure, explaining why the infrared spike was so short-lived.

— Mike Wall,

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