NASA's NEOWISE mission has recently detected two celestial objects approaching Earth, one of which is the 2016 WF9, which is in a blurry line between a comet and an asteroid.

NEOWISE first observed 2016 WF9 on Nov. 27, 2016. The object follows a path that takes it from Jupiter to inside the Earth's orbit over a course of 4.9 years.

It is expected to approach the Earth's orbit on Feb. 25, when it will fly by at a distance of almost 32 million miles or 51 million kilometers from the planet. The proximity is not particularly close to pose any threat of collission with Earth.

Astronomers have been curious about the object since its discovery because its characteristics make it straddle between being identified as distinctly asteroid or comet.

Characteristics Of Comets

NASA describes comets as cosmic snowballs made of frozen gases, rock, and dust that are typically the size of a small town. When they get close to the sun, comets heat up and release dust and gases.

In 2015, the European Space Agency's (ESA) Rosetta probe caught comet 67P producing a cosmic burp of gas and dust, which was attributed to the warming of the body as it got closer to the sun.

2016 WF9 Not Distinctly A Comet

The object 2016 WF9 is believed to be about 0.5 to 1 kilometer in diameter, or 0.3 to 0.6 miles. It has dark appearance and reflects only a small amount of the light that hits its surface. Its reflectivity and orbit are consistent with those observed in other comets but it lacks the distinct cloud of dust and gas that comets are known for.

Astronomers said that bodies in the type of orbit that 2016 WF9 follows have multiple origins, which means that 2016 WF9 may have once been a comet. It may have also strayed from a group of dark objects in the main asteroid belt.

James Bauer, from Jet Propulsion Laboratory in Pasadena, California, said that the object may have cometary origins.

"Perhaps over time this object has lost the majority of the volatiles that linger on or just under its surface," Bauer said.

If scientists confirm that 2016 WF9 is a comet, it would be the 10th comet to be discovered by NEOWISE since December 2013, after the mission was brought out of hibernation to find and learn more about near-Earth objects that may possibly pose impact hazards to Earth.

If the object turns out to be an asteroid, it will be the 100th asteroid discovered by NEOWISE since its reactivation.