Comet U1 NEOWISE: A Possible Binocular Comet?

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

Preview: Comet 45P/Honda–Mrkos–Pajdušáková Brightens in December

Comet 45P/Honda-Mrkos-Pajdušáková From October 1st, 2011 taken with a 10"/3.8 Newtonian and CCD imager. Image credit and copyright: Michael Jäger.

Looking for a good binocular comet? Well, if luck is on our side, we should be getting our first looks at periodic Comet 45P/Honda-Mrkos-Pajdušáková as it tops +10th magnitude in dusk skies over the next few weeks. 

Image credit: Starry Night.
The swift path of Comet 45P/Honda-Mrkos-Pajdušáková on the nights of February 9th to February 12th. Image credit: Starry Night.

Comet 45P/Honda-Mrkos-Pajdušáková is expected to reach maximum brightness around late February 2017. Discovered independently by astronomers Minoru Honda, Antonin Mrkos and L’udmila Pajdušáková on December 3rd, 1948, Comet 45P/Honda-Mrkos-Pajdušáková orbits the Sun once every 5.25 years on a short period orbit. Comet 45P/Honda-Mrkos-Pajdušáková is set to break binocular +10th magnitude brightness in mid-December 2017, and may reach a maximum brightness of magnitude +7 from January through February 2017.

Slovak astronomer ?udmila Pajdušáková
Slovak astronomer ?udmila Pajdušáková, co-discoverer of 5 comets, including Comet 45P/Honda-Mrkos-Pajdušáková. Image credit: The Skalnaté Pleso Observatory.

Currently and through the end of 2016, the comet sits towards the center of the Milky Way Galaxy in Sagittarius at a faint +15th magnitude in the evening sky. The comet may break +10th magnitude and become very briefly visible in the first few weeks of December before getting too close to the Sun to observe in late 2016 and crossing into the morning sky in early 2017.

The path of Comet 45/P from mid-November through December 15th, 2016. Image credit: Starry Night.
The path of Comet 45/P from mid-November through December 15th, 2016. Image credit: Starry Night.

Visibility prospects: At its brightest, Comet 45P/Honda-Mrkos-Pajdušáková will be passing through the constellation Hercules during closest approach on February 11th. The comet then passes through the constellations of Corona Borealis, Boötes, Canes Venatici, Ursa Major into Leo through to the end of February as it recedes. In the second week of February, the comet is visible in the dawn sky 82 degrees west of the Sun at maximum brightness. This apparition favors the northern hemisphere. The comet will reach perihelion on December 29th, 2016 at 0.53 Astronomical Units (AU) from the Sun, and the comet passes just 0.08 AU (7.4 million miles) from the Earth on February 11th at 14:44 UT. The comet made a slightly closer pass in 2011, and was a fine binocular object that time around. At its closest, the comet will cross nine degrees of sky from one night to the next. Some notable dates for comet 45P/Honda-Mrkos-Pajdušáková are:

November 23rd: Venus passes 6′ from the comet.

December 12th: May break 10th magnitude.

December 14th: Passes near M75.

December 15th: Crosses into the constellation Capricornus.

January 4th: Passes near the +4th magnitude star Theta Capricorni

January 10th: Crosses the ecliptic northward.

January 16th: Passes into Aquarius.

January 22nd: Passes near NGC 7009, M72 and M73.

January 25th: Passes 8 degrees from the Sun and into the dawn sky.

January 28th: Crosses into Aquila.

February 3rd: Crosses the celestial equator northward.

February 4th: Passes 4′ from the star +3.3 magnitude star Delta Aquilae.

February 6th: Crosses the Galactic equator.

February 7th: Crosses into Ophiuchus.

February 9th: Crosses into Hercules.

February 16th: makes a wide pass near M3.

February 19th: Drops back below +10th magnitude.

Image credit: NASA/JPL.
The path of Comet 45P/Honda-Mrkos-Pajdušáková through the inner solar system. Image credit: NASA/JPL.

This is the final close (less than 0.1 AU) passage of Comet 45P/Honda-Mrkos-Pajdušáková near the Earth for this century.

On July 1st 1770, Comet D/1770 L1 Lexell passed 0.0151AU from the Earth; a comet in 1491 may have passed closer. Next year’s passage of 45P/Honda-Mrkos-Pajdušáková ranks as the 21st closest passage of a comet near the Earth.

The light curve of Comet 45/P
The light curve of Comet 45/P Honda-Mrkos-Pajdušáková. Credit: Seiichi Yoshida’s Weekly Information About Bright Comets.

Why do comets end up with such cumbersome names? Well, comets derive their names from the first three discovers that submit the find within a 24 hour period to the Minor Planet Center’s Central Bereau for Astronomical Telegrams, which, in fact, received its last ‘telegram’ during the discovery of Comet Hale-Bopp around two decades ago. Increasingly, comets are receiving names of all sky surveys such as LINEAR and PanSTARRS from robotic competition against amateur hunters. It does seem like you need an umlaut or the chemical symbol for boron to in your moniker to qualify these days… rare is the ‘Comet Smith.’ But hey, it’s still fun to watch science journalists try and spell the Icelandic volcano Eyjafjallajökull and comet Churyumov-Gerasimenko over and over… Perhaps, we should insist that our first comet discovery is actually spelled Comet Dîckînsðn…

And Comet 45/P is just one of the fine binocular comets on deck for 2017. We’re also expecting Comet 41P/Tuttle-Giacobini-Kresák, 2/P Encke, C/2015 ER61 PanSTARRS Comet C/2015 V2 Johnson to break +10th magnitude next year… and the next great naked eye ‘Comet of the Century’ could light up the skies at any time.

Goldstone radar pings comet 45/P back in 2011. Image credit: NASA.
Goldstone radar pings comet 45/P back in 2011. Image credit: NASA.

Binoculars are the best tool to observe bright comets, as they allow you to simply sweep the star field and admire the full beauty of a comet, coma, tail(s) and all. Keep in mind, a comet will often appear visually fainter than its quoted brightness… this is because, like nebulae, that intrinsic magnitude is ‘smeared out’ over an extended area. To my eye, a binocular comet often looks like a fuzzy, unresolved globular cluster that stubbornly refuses to snap into focus.

Don’t miss your first looks at Comet 45/P 45P/Honda-Mrkos-Pajdušáková, as it spans 2016 into 2017.

A Summer Comet: Our Guide to Observing X1 PanSTARRS

Comet X1 PanSTARRS
Comet C/2013 X1 PanSTARRS from early January 2016, shortly after a reported outburst. Image credit and copyright: Hisayoshi Kato.

Ready for one of the better binocular comets of 2016? Emerging from behind the Sun and a surprise outburst in January, Comet C/2013 X1 PanSTARRS is about to put on its summer show. The waning crescent Moon just crossed paths with the comet in the dawn sky on its way to New on May 6th, and the time to start tracking it is now as it plunges southward across the ecliptic this weekend. Continue reading “A Summer Comet: Our Guide to Observing X1 PanSTARRS”

Comet US10 Catalina: The Final Act

Comet US10 Catalina passes near the bright star Arcturus on January 1st. Image credit and copyright: Alan Tough

Have you seen it? 2016 has kicked off with a fine apparition of a binocular comet: C/2013 US10 Catalina. We’ve been following this icy visitor to the inner solar system the first few mornings of the year, a welcome addition to the morning planetary line-up. Continue reading “Comet US10 Catalina: The Final Act”

Catch This Season’s ‘Other’ Comet: S2 PanSTARRS

Comet C/2014 S2 PanSTARRS, imaged on October 10th, 2015. Image credit and copyright: Tom Wildoner

Now is the time to catch binocular Comet C/2014 S2 PanSTARRS, as it tops +8 magnitude ahead of predictions this month and crosses circumpolar northern skies. Will this Christmas comet stay bright post-perihelion, rivaling other comets into early 2016?  Continue reading “Catch This Season’s ‘Other’ Comet: S2 PanSTARRS”

Comet US10 Catalina: Our Guide to Act II

Image credit and copyright:

Itching for some cometary action? After a fine winter’s performance from Comet C/2014 Q2 Lovejoy, 2015 has seen a dearth of good northern hemisphere comets. That’s about to change, however, as Comet C/2013 US10 Catalina joins the planetary lineup currently gracing the dawn sky in early November. Currently located in the constellation Centaurus and shining at magnitude +6, Comet US10 Catalina has already put on a fine show for southern hemisphere observers over the last few months during Act I

Currently buried in the dusk sky, Comet US10 Catalina is bashful right now, as it shares nearly the same right ascension with the Sun over the next few weeks, passing just eight degrees from our nearest star as seen from our Earthly vantage point on November 7th — and perhaps passing juuusst inside of the field of view for SOHO’s LASCO C3 camera — and into the dawn sky.

Image credit:
The altitude of Comet US10 Catalina in November and December at dawn as seen from latitude 30 degrees north. Image credit: Starry Night Education software.

The hunt is on come early November, as Comet US 10 Catalina vaults into the dawn sky. From 30 degrees north latitude here in Central Florida, the comet breaks 10 degrees elevation an hour prior to local sunrise right around November 20th. This should see the comet peaking in brightness right around magnitude +5 near perihelion the same week on November 16th.

Image credit:
The projected light curve of Comet US10 Catalina, with observations thus far (black dots) Image credit: Adapted from Seiichi Yoshida’s Weekly Information About Bright Comets

The angle of the comet’s orbit is favorable for northern hemisphere viewers in mid-November, as viewers start getting good looks in the early morning from latitude 30 degrees northward and the comet gains about a degree of elevation per day. This will bring it up out of the murk of twilight and into binocular view.

Mark your calendar for the morning of December 7th, as the crescent Moon, Venus and a (hopefully!) +5 magnitude comet US10 Catalina will all fit within a five degree circle.

Image credit:
The view on the morning of December 7th. Image credit: Starry Night Education software

Here are some key dates with celestial destiny for Comet US10 Catalina for the remainder of 2015:


20-Crosses into the constellation Hydra.


2-Crosses into the constellation Libra.

16-Crosses into the constellation Virgo.

16-Reaches perihelion at 0.823 AU (127.6 million kilometers) from Sun.

26-Crosses the ecliptic plane northward.

27-Passes less than one degree from the +4.5 magnitude star Lambda Virginis.

Image Credit:
The celestial path of Comet US 10 Catalina through the end of 2015. Image Credit: Starry Night Education software


7-Fits inside a five degree circle with Venus and the waning crescent Moon.

8-Passes less than one degree from the +4 magnitude star Syrma (Iota Virginis).

17-Crosses the celestial equator northward.

24-Crosses into the constellation Boötes.

In January, Comet US10 Catalina starts the New Year passing less than a degree from the -0.05 magnitude star Arcturus. From there, the comet may drop below +6 magnitude and naked eye visibility by mid-month, just prior to its closest approach to the Earth at 0.725 AU (112.3 million kilometers) on January 17th. By February 1st, the comet may drop below +10th magnitude and binocular visibility, into the sole visual domain of large light bucket telescopes under dark skies.

Image credit:
Comet US10 Catalina imaged from Australia on July 21st, 2015. Image credit: Alan Tough

Or not. Comets and predictions of comet brightness are always notoriously fickle, and rely mainly on just how the comet performs near perihelion. Then there’s twilight extinction to contend with, and the fact that the precious magnitude of the comet is diffused over its extended surface area, often causing the comet to appear fainter visually than the quoted magnitude.

But do not despair. Comets frequently under-perform pre-perihelion passage, only to put on brilliant shows after. Astronomers discovered Comet US10 Catalina on Halloween 2013 from the Catalina Sky Survey based just outside of Tucson, Arizona. On a several million year orbit, all indications are that Comet US10 Catalina is a dynamically new Oort Cloud visitor and will probably get ejected from the solar system after this all-too brief fling with the Sun. Its max velocity at perihelion will be 46.4 kilometers per second, three times faster than the New Horizons spacecraft currently on an escape trajectory out of the solar system.

The odd ‘US10’ designation comes from the comet’s initial identification as an asteroidal object, later upgraded to cometary status.  The comet’s high orbital inclination of 149 degrees assured two separate showings, as the comet approached the Sun as seen from the Earth’s southern hemisphere, only to then vault up over the northern hemisphere post-perihelion. As is often the case, the comet was closest to the Sun at exactly the wrong time: had perihelion occurred around May, the comet would’ve passed the Earth just 0.17 AU (15.8 million miles or 26.3 million kilometers) distant! That might’ve placed the comet in the negative magnitudes and perhaps earned it the title of ‘the Great Comet of 2015…’

Image credit:
The orbit of Comet US10 Catalina and the view during closest Earth approach. Image credit: NASA/JPL

But such was not to be.

Ah, but the next ‘big one’ could come at any time. In 2016, we’re tracking comet C/2013 X1 PanSTARRS, which will ‘perhaps’ become a fine binocular comet next summer…

More to come. Perhaps we’ll draft up an Act III for US10 Catalina in early January if it’s a top performer.