5, 2019, by the NASA-funded Asteroid Terrestrial-Impact Last Alert System (ATLAS) telescope in Hawaii. The initial clue was the fortuitous detection of the first debris tail, observed on Jan.
All-sky surveys, ground-based telescopes, and space-based facilities like the Hubble Space Telescope pooled their efforts to make this discovery possible. Piecing together Gault's recent activity is an astronomical forensics investigation involving telescopes and astronomers around the world. The researchers estimate that Gault could have been slowly spinning up for more than 100 million years. When the resulting centrifugal force starts to overcome gravity, the asteroid's surface becomes unstable, and landslides may send dust and rubble drifting into space at a couple miles per hour, or the speed of a strolling human. This process creates a tiny torque that can cause the asteroid to continually spin faster. (YORP stands for "Yarkovsky-O'Keefe-Radzievskii-Paddack," the names of four scientists who contributed to the concept.) When sunlight heats an asteroid, infrared radiation escaping from its warmed surface carries off angular momentum as well as heat. Gault is only the second asteroid whose disintegration has been strongly linked to a process known as a YORP effect. All the large grains (about the size of sand particles) are close to the object and the smallest grains (about the size of flour grains) are the farthest away because they are being pushed fastest by pressure from sunlight." "We just had to look at the image of the streamers, and we can see all of the dust grains well-sorted by size. "We didn't have to go to Gault," explained Olivier Hainaut of the European Southern Observatory in Germany, a member of the Gault observing team. Watching an asteroid become unglued gives astronomers the opportunity to study the makeup of these space rocks without sending a spacecraft to sample them. Of the roughly 800,000 known asteroids between Mars and Jupiter, astronomers estimate that this type of event in the asteroid belt is rare, occurring roughly once a year. Gault is located 214 million miles (344 million kilometers) from the Sun. Each tail represents an episode in which the asteroid gently shed its material - key evidence that Gault is beginning to come apart.ĭiscovered in 1988, the 2.5-mile-wide (4-kilometer-wide) asteroid has been observed repeatedly, but the debris tails are the first evidence of disintegration.
Images from Hubble show two narrow, comet-like tails of dusty debris streaming from the asteroid (6478) Gault.
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