Published : Monday, January 2, 2017 | 7:45 PM
JPL’s NEOWISE mission has detected two celestial objects approaching Earth, one of which will approach Earth’s orbit in February. The good news is, at a distance of nearly 32 million miles from Earth, this pass will not bring it particularly close. The object, JPL says, is not a threat to Earth for the foreseeable future.
NEOWISE (Near-Earth Object, Wide-Field Infrared Survey Explorer) first observed the object, which is in a blurry line between a comet and an asteroid, on November 27. The object follows a path that takes it from Jupiter to inside the Earth’s orbit over a course of 4.9 years.
The object, called 2016 WF9, is expected to approach the Earth’s orbit on February 25, 2017.
Astronomers have been curious about 2016 WF9 since November because its characteristics make it straddle between being identified as distinctly asteroid or comet. The object is believed to be about 0.5 to 1 kilometer in diameter, or 0.3 to 0.6 miles.
The object 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.
“2016 WF9 could have cometary origins,” said Deputy Principal Investigator James Bauer at 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.”
If scientists confirm that 2016 WF9 is a comet, it would be the 10th comet to be discovered by NEOWISE since December 2013 when the program was reactivated. If the object turns out to be an asteroid, it will be the 100th asteroid discovered by NEOWISE.
A different object, C/2016 U1 NEOWISE, discovered a month earlier, is more clearly a comet, releasing dust as it nears the sun.
The comet “has a good chance of becoming visible through a good pair of binoculars, although we can’t be sure because a comet’s brightness is notoriously unpredictable,” says Paul Chodas, who manages NASA’s Center for Near-Earth Object (NEO) Studies at JPL.
As seen from the northern hemisphere during the first week of 2017, comet C/2016 U1 NEOWISE will be in the southeastern sky shortly before dawn. It is moving farther south each day and it will reach its closest point to the sun, inside the orbit of Mercury, on January 14. It will then head back out to the outer reaches of the solar system for an orbit lasting thousands of years.
While it will be visible to skywatchers on Earth, C/2016 U1 NEOWISE is not considered a threat to the planet either.
NEOWISE is the asteroid-and-comet-hunting portion of the WISE mission. After discovering more than 34,000 asteroids during its original mission, NEOWISE was brought out of hibernation to find and learn more about asteroids and comets that could pose an impact hazard to Earth.