Rare asteroid-comet hybrid space rock with 720000 km-long tail baffles astronomers

A rare space body discovered recently has left astronomers in splits. The space rock exhibits properties of both asteroids and comets.

The space rock belongs to the main asteroid belt which has over 5 lakh asteroids. The unique space rock has been seen active on a few occasions. The main-belt asteroids don’t change structure but the hybrid rock 2005 QN173 is shedding dust in a long tail of 7,20,000 kilometers.

This suggests that the rare body is covered with icy matter and sheds the vapourised material as it actively travels through the solar system. The discovery was made a few months ago in July during the Asteroid Terrestrial-Impact Last Alert System (ATLAS) survey.

In a recent paper unveiled at the American Astronomical Society’s Division for Planetary Sciences 53rd annual meeting, the space rock can be categorized both as an asteroid and a comet.

First detected in 2005, the main-belt asteroid travels encircled by a dust cloud spanning 3.2 kilometers across. In July 2021, its tail’s length was estimated to be longer than 7,20,000 kilometers, nearly double of the distance between the Earth and the Moon. However, the tail’s width is notably small at just 1,400 kilometers across.

Why the space rock is a rare discovery?

Unlike other comets which have an icy tail due to the fact that they arrive from the cold environment of the outer solar system beyond Neptune’s orbit, 2005 QN173 is a main-belt asteroid. Main-belt asteroids lose their icy matter as they are close to the sun.

But 2005 QN173 has a long tail of ice and dust even when it is spotted in the main asteroid belt between Jupiter and Mars. This contradicts its existence in the main belt.