Close brush with comet

Washington: The National Aeronautics and Space Administration’s (Nasa) asteroid- and comet-hunting NEOWISE project has detected a mysterious object hurtling towards the Earth.

The object has been named C/2016 U1 NEOWISE. Nasa has pinpointed it as a comet, but the other, dubbed 2016 WF9, has left it slightly more baffled, according to The Sun. The comet is set to fly close to Earth this week, but the mystery object isn’t expected to make an appearance till February.

On 25 February, WF9 will approach Earth's orbit at a distance of nearly 51 million kilometres from our home planet. The object is “not a threat to Earth for the foreseeable future”, Nasa said. Nasa says chances are that it could be visible using a good pair of binoculars. However, the visibility isn’t guaranteed because the space agency isn’t able to predict the comet’s brightness.

“2016 WF9 could have cometary origins,” said deputy principal investigator James ‘Gerbs’ Bauer at Nasa’s JPL. “This object illustrates that the boundary between asteroids and comets is a blurry one; perhaps, over time this object has lost the majority of the volatiles that linger on or just under its surface.”

While 2016 WF9 is dark like a comet, it appears to lack the characteristic dust and gas cloud that defines a comet. The comet is moving farther away in the south with each passing day and once it reaches its closest point to the Sun on January 14 it will start an outward journey that will take it beyond the outer solar system and won’t be visible for thousands of years to come.

At its farthest distance from the Sun, WF9 it approaches Jupiter’s orbit. Over the course of 4.9 Earth-years, it travels inward, passing under the main asteroid belt and the orbit of Mars until it swings just inside Earth’s own orbit. After that, it heads back toward the outer solar system. Nasa explains that objects similar to WF9 have multiple possible origins; it might once have been a comet, or it could have strayed from a population of dark objects in the main asteroid belt.

At a distance of nearly 51 million kilometres from Earth, this pass will not bring it particularly close. The trajectory of WF9 is well understood, and the object is not a threat to Earth for the foreseeable future. WF9 is relatively large: roughly 0.5 to 1 kilometre across. It is also rather dark, reflecting only a few percent of the light that falls on its surface. This body resembles a comet in its reflectivity and orbit, but appears to lack the characteristic dust and gas cloud that defines a comet.