NASA | GSFC | STScI | HubbleSite | 2019 Mar 28
A small asteroid has been caught in the process of spinning so fast it’s throwing off material, according to new data from NASA’s Hubble Space Telescope and other observatories.This Hubble Space Telescope image reveals the gradual self-destruction of an asteroid,
whose ejected dusty material has formed two long, thin, comet-like tails. The longer
tail stretches more than 500,000 miles (800,000 kilometers) and is roughly 3,000 miles
(4,800 kilometers) wide. The shorter tail is about a quarter as long. The streamers will
eventually disperse into space. Credits: NASA, ESA, K. Meech and J. Kleyna
(University of Hawaii), and O. Hainaut (European Southern Observatory)
Images from Hubble show two narrow, comet-like tails of dusty debris streaming from the asteroid (6478) Gault. Each tail represents an episode in which the asteroid gently shed its material — key evidence that Gault is beginning to come apart.
Discovered 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. Gault is located 214 million miles (344 million kilometers) from the Sun. 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.
Watching an asteroid become unglued gives astronomers the opportunity to study the makeup of these space rocks without sending a spacecraft to sample them. ...
Gault is only the second asteroid whose disintegration has been strongly linked to a process known as a YORP effect. (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. This process creates a tiny torque that can cause the asteroid to continually spin faster. 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. The researchers estimate that Gault could have been slowly spinning up for more than 100 million years. ...
Hubble Captures Rare Active Asteroid
ESA Hubble Science Release | 2019 Mar 28
Hawaiʻi Team Catches Asteroid As It Self-Destructs
Institute for Astronomy | University of Hawaii | 2019 Mar 28
The Sporadic Activity of (6478) Gault: A YORP-driven event? ~ Jan T. Kleyna et al