Images taken by NASA's Hubble Space Telescope revealed that an unusual object in the asteroid belt previously believed to be a comet is, in fact, a pair of asteroids orbiting each other.
Initially Thought To Be An Asteroid
The two asteroids, collectively called 2006 VW139/288P, were discovered in November 2006 by the Spacewatch astronomical survey and was initially thought to be an asteroid. It was dubbed Asteroid 300163 (2006VW139). It was renamed 288P after the Pan-STARRS telescope observed cometary activity in 2011.
Young Binary System
Although the peculiar space rocks were initially thought of as a single object, follow-up observation showed that it consists of two asteroids, each estimated to be about 1 km wide, and orbiting each other.
Astronomers also think that the pair has existed as a binary system for only about 5,000 years. The most feasible explanation for the setup is a breakup caused by fast rotation.
Unusual Pair In The Asteroid Belt
The pair of space rocks do not behave like anything earlier observed in the asteroid belt between Jupiter and Mars.
The two asteroids have comet-like features such as a bright coma and a long tail but unlike many asteroids in the region which can either orbit another space rock, or release water vapor, 2006 VW139/288P has both these features.
Another thing that made the pair different from other objects of their size in the region is that they orbit much farther apart. They circle each other at a distance of about 100 km, which is at least 10 times farther apart than how models predict they should be.
"288P is a binary main-belt comet. It is different from the known asteroid binaries for its combination of wide separation, near-equal component size, high eccentricity, and comet- like activity," the researchers reported in the journal Nature.
Bizarre Orbital Characteristics
The rocks' orbits are also eccentric in that these are very elongated instead of being closer to a perfect circle. Scientists said that the pair's orbital characteristics are different from all other known asteroid binaries.
The bizarre orbital characteristics of the system suggest that multiple factors may have contributed to the motion of these objects.
"The uniqueness of 288P is the combination [of factors]," said study researcher Jessica Agarwal, from the Max Planck Institute for Solar System Research.
Implications On Our Understanding Of Solar System And Earth
Researchers said that the origin and evolution of the binary asteroid may offer more insights about the formation of the solar system and the planet Earth.
"Understanding its origin and evolution may provide new insights into the early days of the solar system. Main-belt comets may help to answer how water came to a bone-dry Earth billions of years ago," NASA said.