A strange asteroid behaving like a comet that was first discovered more than 10 years ago has turned out to be stranger than scientists had initially thought. They have learned that it actually consists of two asteroids that are orbiting each other.
In a study published in the journal Nature, a team led by Jessica Agarwal of the Max Planck Institute for Solar System Research in Germany, confirm that the pair of asteroids are the first known binary asteroid which can also be classified as a comet.
The binary asteroid, called 2006 VW139/288P, was initially spotted by the University of Arizona’s Spacewatch program back in 2006. The kilometer-wide object was seen in the main asteroid belt between Mars and Jupiter.
Scientists noticed its comet-like features through the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) at Hawaii’s Haleakala Observatory in 2011 as it was about to approach perihelion – its closest orbital position to the Sun.
As it was making its closest approach to the Sun, the astronomers looked in further with the use of the Hubble Space Telescope. The new images it generated showed that the 2006 VW139/288P is actually made up of two asteroids that are almost similar in mass and size. In addition, they orbit each other at a distance of around 100 kilometers.
The images from the Hubble Telescope also confirmed its activity in the binary system, including a bright comet-like coma of material which surrounds the asteroid and streams into a long tail. However, a few days after, the tail started pointing away from the Sun and the particle size has been reduced to only 10 microns. This is similar to how a comet would behave.
“We detected strong indications for the sublimation of water ice due to the increased solar heating — similar to how the tail of a comet is created,” explained team leader Jessica Agarwal of the Max Planck Institute for Solar System Research, Germany.
There have been about 20 asteroids similar to the 288P discovered, but this is so far the only one considered to be a binary system.