An asteroid discovered decades ago may have become a comet in recent months, according to telescope observations that spotted a tail accompanying the space rock.

The newly intriguing object is named Asteroid (6478) Gault, and observations from December and early January show it has developed a tail. 

A notice sent to astronomers by the International Astronomical Union said that data from the observations is "consistent with the ejection of material or commencement of activity in early Nov. 2018."

British astronomer Alan Fitzsimmons noted on Twitter that the tail of dust extends over 400,000 km (249,000 miles).

"A possible scenario is that there was a collision between Gault and another object, releasing material into space, that we see like a tail/trail," astronomer Gianluca Masi said in a blog post for the Virtual Telescope Project, which managed to catch the object with its Italy-based telescope. 

Masi and other astronomers plan to keep a close eye on the asteroid to see whether it's beginning a new life as a comet or will revert back to being just a regular rock drifting around the asteroid belt. 

Although Gault is a rather large asteroid almost 2.3 miles (3.7 km) in diameter, it poses no threat to Earth, orbiting beyond Mars in the inner asteroid belt.