NASA’s NEOWISE Missions Spots New Comets

NASA’s Wide-field Infrared Survey Explorer (WISE) accomplished much during its first mission, which ran from December of 2009 to September of 2010. During the many months that it was active, the orbital telescope conducted an all-sky astronomical survey in the infrared band and discovered thousands of minor planets and numerous star clusters.

The extension of its mission, NEOWISE, has brought new life to the telescope as a comet and asteroid hunter. And since its re-activation in December of 2013, the orbiting telescope has spotted hundreds of Near Earth Objects (NEOs) and thousands of Main Belt asteroids. Most recently, it has detected two new objects (both possibly comets) which could be observable from Earth very soon.

The most recent object to be detected – 2016 WF9 – was first observed by NEOWISE on November 27th, 2016. This comet’s path through the Solar System takes it on a circuitous route, taking it from Jupiter to just inside the orbit of Earth over the course of 4.9 years. Much like other objects of its kind, 2016 WF9 may have once been a comet, or part of a  population of dark objects in the Main Asteroid Belt.

Artist’s rendition of the comet 2016 WF9 as it passes Jupiter’s orbit and moves toward the sun. Credit: NASA/JPL-Caltech

In any case, 2016 WF9 will approach Earth’s orbit on February 25th, 2017, passing Earth at a minimum distance of almost 51 million km (32 million mi). This will place it well outside the orbit of the Moon, so the odds of it threatening Earth are negligible. But for those keen observers hoping to catch sight of the object, it will be close enough that it might be visible with just a pair of binoculars.

Since its discovery, 2016 WF9 has been of interest to astronomers, mainly because it straddles the already blurry line between asteroids and comets. While its proportions are known – roughly 0.5 to 1 kilometer in diameter (0.3 to 0.6 miles) – its other characteristics have led to some confusion as to where it came from. For one, its appearance (which is quite dark) and its orbit are consistent with what one expects from a comet.

But on the other hand, it lacks the characteristic cloud of dust and gas that comets are known for. As James Bauer, NEOWISE’s Deputy Principal Investigator at JPL, said in a NASA press release:

“2016 WF9 could have cometary origins. 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.”

Graphic showing the asteroids and comets observed by NASA’s Near-Earth Object Wide-field Survey Explorer (NEOWISE) mission. Credit: NASA/JPL-Caltech/UCLA/JHU

The other object, C/2016 U1 NEOWISE, was discovered about a month prior to 2016 WF9. Its orbit, which can you see by checking out the 3D Solar System Simulator, takes it from the outer Solar System to within Mercury’s orbit over the course of thousands of years. According to NASA scientists, this object is very clearly a comet, as evidenced by the dust it has been releasing as it gets closer to our Sun.

During the first week of 2017, comet C/2016 U1 NEOWISE is also likely to be visible in the night sky – in this case, in the southeastern sky shortly before dawn (for those looking from the northern hemisphere). It will reach its closest point to the Sun on January 14th (where it will be passing within Mercury’s orbit) before heading back out towards the outer Solar System.

Once again, it is believed that comet-hunters should be able to see it, though that is open to question. Paul Chodas, the manager of NASA’s Center for Near-Earth Object (NEO) Studies at the Jet Propulsion Laboratory, thinks that this object “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.”

A mosaic of the images covering the entire sky as observed by the Wide-field Infrared Survey Explorer (WISE), part of its All-Sky Data Release. Credit: NASA/JPL

In any case, NASA will be continuing to monitor 2016 WF9 to see if they can’t sort out what it is. Should it prove to be a comet, it would be the tenth discovered by NEOWISE since it was reactivated in December of 2013. If it turns out to be an asteroid, it would be the one-hundredth discovered since its reactivation.

As of November 2016, the orbital telescope has conducted over 562,000 infrared measurements have been made of 24,024 different solar system objects, including 613 NEOs and 110 comets. It has also been responsible for discovering 249 new near-Earth objects and comets, as well as more than 34,000 asteroids during its original mission.

At present, NEOWISE’s science team is currently reprocessing all its primary mission data to extend the search for asteroids and comets. It is hoped that by taking advantage of the latest in photometric and astrometric calibrations, they will be able to push the limits of what the telescope can detect, thereby adding many more minor planets and objects to its suite of discoveries.

And be sure to enjoy this video, detailing the first two years of asteroid data collected by the NEOWISE mission:

Further Reading: NASA

Comet U1 NEOWISE: A Possible Binocular Comet?

Comet C/2016 U1 NEOWISE on December 23rd as seen from Jauerling, Austria. Image credit: Michael Jäger.

Well, it looks like we’ll close out 2016 without a great ‘Comet of the Century.’ One of the final discoveries of the year did, however, grab our attention, and may present a challenging target through early 2017: Comet U1 NEOWISE.

Comet C/2016 U1 NEOWISE is expected to reach maximum brightness during the second week on January. Discovered by the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) space observatory on its extended mission on October 21st, 2016, Comet U1 NEOWISE orbits the Sun on an undefined hyperbolic orbit that is perhaps millions on years long. This also means that this could be Comet C/2016 U1 NEOWISE’s first venture through the inner solar system. Comet C/2016 U1 NEOWISE is set to break binocular +10th magnitude brightness this week, and may just top +6th magnitude (naked eye brightness) in mid-January near perihelion.

The orbit of Comet U1 NEOWISE. Credit: NASA/JPL.

Visibility prospects: At its brightest, Comet C/2016 U1 NEOWISE will pass through the constellations Ophiuchus to Serpens Cauda and Sagittarius, and is best visible in the dawn sky 12 degrees from the Sun at maximum brightness. This apparition favors the northern hemisphere. Perihelion for Comet C/2016 U1 NEOWISE occurs on January 13th, 2017 at 0.319 AU from the Sun, and the comet passed 0.709 AU from the Earth on December 13th.

This is the ninth comet discovered by the extended NEOWISE mission since 2014.

The pre-dawn view on the morning of December 28th. Image credit: Starry Night.

Comet C/2016 U1 NEOWISE ends 2016 and early January 2017 as a difficult early dawn target, sitting 25 degrees above the eastern horizon as seen from latitude 30 degrees north about 30 minutes before dawn. Things will get much more difficult from there, as the comet passes just 12 degrees from the Sun as seen from our Earthly vantage point during the final week of January. The comet sits 16 degrees from the Sun in the southern hemisphere constellation of Microscopium on the final day of January, though it is expected to shine at only +10th magnitude at this point, favoring observers in the southern hemisphere.

The time to try to catch a brief sight of Comet C/2016 U1 NEOWISE is now. Recent discussions among comet observers suggest that the comet may be slowing down in terms of brightness, possibly as a prelude to a pre-perihelion breakup. Keep a eye on the Comet Observer’s database (COBS) for the latest in cometary action as reported and seen by actual observers in the field.

Finding C/2016 U1 NEOWISE will be a battle between spying an elusive fuzzy low-contrast coma against a brightening twilight sky. Sweep the suspect area with binoculars or a wide-field telescopic view if possible.

The path of Comet U1 NEOWISE through perihelion on January 13th. Credit: Starry Night.

Here are some key dates to watch out for in your quest:


25-Crosses in to Ophiuchus.

26-Passes near +3 mag Kappa Ophiuchi.


1-Crosses the celestial equator southward.

3-Passes near M14.

7-Passes near the +3 mag star Nu Ophiuchi.

8-Crosses into the constellation Serpens Cauda.

10-Passes near M16, the Eagle Nebula.

11-Passes near M17 the Omega Nebula, crosses the galactic equator southward.

12-Crosses into the constellation Sagittarius.

13-Passes near M25.

16-Crosses the ecliptic southward.

27-Crosses into the constellation Microscopium.

28-Passes near +4.8 mag star Alpha Microscopii.


1-May drop back below +10 magnitude.

C/2016 U1 NEOWISE (23.nov.2016) from Oleg Milantiev on Vimeo.

A rundown on comets in 2016, a look ahead at 2017

C/2016 U1 NEOWISE was one of 50 comets discovered in 2016. Notables for the year included C/2013 X1 PanSTARRS, 252/P LINEAR and C/2013 US10 Catalina. What comets are we keeping an eye on in 2017? Well, Comet 2/P Encke, 41P/Tuttle-Giacobini-Kresak, C/2015 ER61 PanSTARRS, C/2015 V2 Johnson are all expected to reach +10 magnitude brightness in the coming year… and Comet 45P/Honda-Mrkos-Pajdušáková has already done so, a bit ahead of schedule. These are all broken down in our forthcoming guide to the top 101 Astronomical Events for 2017. Again, there’s no great naked eye comet on the horizon (yet), but that all could change… 2017 owes us one!