- Hubble Space Telescope captures a new active asteroid named 6478 Gault.
- The asteroid ejected matter into space (between October and December 2018), leaving behind two long tails.
- The debris from the long tail was captured earlier in December 2018.
Gault was first discovered in 1988 in the inner regions of the asteroid belt. This S-shape asteroid is about 3.7 kilometers in diameters.
Recently, a grand collaboration brought together data from all-sky surveys, ground- and space-based telescopes, including the Hubble Space Telescope (HST). It revealed the 6478 Gault, a scarce self-destructing asteroid.
The new data from HST enabled astronomers to closely look into the asteroid’s strange past. The two narrow, comet-like tails of the asteroid show that the celestial body is gradually undergoing self-destruction. Each tail represents an active event that ejected matter into space.
Gault: A New Active Asteroid
Gault is continuously disintegrating due to a process called YORP effect. When an asteroid receives enough heat from sunlight, it ejects infrared radiation from its surface. This radiation carries heat as well as momentum, which produces a significant force, causing the asteroid to spin faster.
Once the centrifugal force overcomes gravitational force, the asteroid becomes unstable. Avalanches on the body eject dust and rubble into space, which leaves behind a tail of debris. This is what we are seeing in Gault.
There are approximately 800,000 known asteroids in the Asteroid Belt (located between the orbits of Mars and Jupiter), and as per estimates, YORP events take place once a year. Studying such events could help astronomers understand more about the evolution of planets in the early Solar System.
6478 Gault asteroid | Source: NASA, ESA
In the case of Gault, two tails might be formed due to sudden dust ejections between October and December 2018. Debris of longer tail was observed earlier in December 2018, and one month later, the shorter tail was captured by several ground-based telescopes. The larger tail has been estimated to be more than 800,000 kilometers long.
What Did They Conclude?
The follow-up observations revealed the rotation period of Gault: 2 hours. The is very close to the limit of stability for an asteroid: after this point, materials on the asteroid start tumbling and sliding across the body’s surface and eventually they drift off into space.
The sharp and clear images obtained via HST provided valuable insights into Gault’s activity. Since both tails were quite narrow in width, materials from the asteroid would have released in short episodes lasting up to a couple of days. And since there was no sign of excess dust in the Gault’s immediate vicinity, this asteroid activity wasn’t a result of a collision with other massive object(s).
So far, no rotational lightcurve of Gault has been recorded, and its precise pole and shape remain unspecified. Astronomers believed that further observations will uncover more details about this unusual and curious asteroid.