Comet Catalina Sails Into Northern Skies

Comet Catalina returns this month with naked-eye potential. Follow its every move with our guide and finder charts.

Blue Q-tip

Comet Catalina (C/2013 US10) on October 1, 2015, shines near 7th magnitude and shows a greenish coma due to emissions from diatomic carbon (C2). The tail stretched 3° across the rich star fields of Centaurus and Lupus at the time.
José J. Chambó

Get ready to lose some sleep —  Comet Catalina (C/2013 US10) will be arriving soon! After making a hairpin turn around the Sun at perihelion on November 15th, the comet will surge into the dawn sky for Northern Hemisphere skywatchers and put on a great show by month's end. Early on, binoculars will show the comet's small, bright coma with a whisper of a tail. Naked-eye sightings may be possible by mid-December.

Humble Beginnings

Back on March 30th, when the comet first became accessible to amateur astronomers, it was a 13th-magnitude smudge.
Rob Kaufman

There's been a lot of buzz about the comet, since many of us expected Comet Catalina to depart the solar glare pumped up to magnitude 3, making it the brightest expected fuzzball of the year. Maybe it will still. But in September, the comet's rate of brightening began to flag. Revised estimates now call for it to top out between magnitude 5 and 6 by year's end.

From late March through mid-October, Catalina's path confined its visibility to southern eyes only. Chris Wyatt of New South Wales, Australia, made one of the last visual observations on October 16th before the comet disappeared in the solar glare. Using 10×70 binoculars, he estimated a magnitude of 7 with a 7′-wide, well-condensed, greenish coma, and short ion tail pointing southeast.

Through his 10-inch Dobsonian reflector, the coma expanded to 8.2′ with a longer 35′ tail. Wyatt noted that Catalina responded well to a Swan Band filter, a narrow bandpass filter tuned to oxygen and carbon emissions that enhances the view of  gassy (versus dusty) comets. With the filter in place he saw significant brightening in the inner coma.

Just Passing By

C/2013 US10 is an Oort Cloud comet with a steeply inclined orbit of 149°. It's spent much of its time lately below the plane of the solar system, out of view of Northern Hemisphere skywatchers. After solar conjunction at mid-month, it will transition to northern skies and arc over the inner planets. On January 12, 2016, the comet comes closest to Earth at 66.9 million miles (107.7 million km).

Discovered by the Catalina Sky Survey on Halloween 2013, the comet received the "US10" designation because it was initially thought to be an asteroid in a short period orbit. After more observations to refine its path and additional photographs that revealed telltale comet fuzz, astronomers realized they'd run into a denizen from the Oort Cloud, knocked our way by the close passage of some nameless star long ago. At the time of discovery, Catalina glowed at only 19th magnitude some 7.7 a.u. from Earth. Typical of new arrivals, it dove into the inner solar system on a steeply inclined orbit.

Virgin Comet in Virgo

C/2013 US10 spends its first few weeks after conjunction climbing northward through Virgo near Spica. Ticks mark its position at 0h Universal Time every three days. Stars are plotted to 6th magnitude. Click on the image for a large, color PDF map.
Sky & Telescope

The comet pursues a northerly track through Virgo when it returns at dawn around November 24th, appearing 8° high in the southeastern sky 70 minutes before sunrise. By the 28th, it will have climbed to 10° in a dark sky shortly before the start of dawn.

Now for the bad news. A bright Moon will put a temporary damper on the comet's rise to fame from November 24th through December 3rd. From there on out, though, it's smooth sailing until the Moon returns for Round 2 at the winter solstice.

Catalina glides northward at nearly 1° per day in late December as it crosses from Virgo into Boötes on a beeline for Arcturus. On the morning of January 1st, the comet skims ½° southwest of that orange luminary in a remarkable conjunction highlighting the arrival of the new year. Photo anyone?

Northern Dash

After a relatively slow start in Virgo, the comet races across the sky, becoming a circumpolar object in Ursa Major by mid-January and visible all night long from mid-northern latitudes. Click on the image for a large black-and- white PDF chart.
Sky & Telescope

The comet passes closest to Earth at 0.72 a.u. on January 12th, then buzzes Mizar in the Big Dipper's handle on January 14–15, hurrying along at the rate of 2° per day or 5′ an hour — fast enough to easily detect motion in 30 minutes or less. After mid-month, it's expected to fade quickly.

In this dark time of year, when the Sun bows low in the south, we welcome a potentially bright comet to lift our spirits and add celestial pizzazz to the seasonal holidays of Thanksgiving, Christmas, and New Year's.

Who really knows how bright Comet Catalina will get? Will it break into multiple comets after perihelion? First-time visitors from the Oort Cloud often do surprising things. No matter what Catalina has up its sleeve, its tour will be be a brief one.

After several million years of inbound travel, perturbations induced by the planets will boot it out of the solar system and into interstellar space. We're glad for the chance to share our table with a visitor who spent so much time getting here but can only stay a short while.

Comet Catalina highlights:

* November 24 — Approximate date of first visibility in the dawn sky
* December 7 — Catalina gets company! The comet pairs up with the planet Venus and the waning crescent Moon this morning. From the central United States, Venus shines 4° southwest and the Moon 5° southwest of the comet.
* December 23–24 — Comet crosses into Boötes
* January 1, 2016 — Close pass (0.5°) of Arcturus on the first day of 2016
* January 9 — Comet crosses into Canes Venatici
* January 12 — Closest to Earth at 66.9 million miles
* January 14 — Comet crosses into Ursa Major
* January 14–15 — Passes just 1° north of Alkaid, the star at the end of the Big Dipper's handle
* January 16 — Passes 2° southwest of the 8th-magnitude galaxy, M101
* January 17 — Passes 3.4° northeast of the double star Mizar in the bend of the Big Dipper's handle
* January 21 — Comet crosses into Draco
* January 25 — Comet crosses into Camelopardalis

Plan your observing year with SkyWatch 2016 from Sky & Telescope, available in print and digital editions!

10 thoughts on “Comet Catalina Sails Into Northern Skies

  1. JL

    It would be great if S&T could include maps color-switchable to black-on-white. Some of us print maps for use at the eyepiece!

    1. Anthony BarreiroAnthony Barreiro

      By clicking on the second chart in this article you will get a printable black-on-white chart.

      Thanks Bob for a very informative article and for the printable chart. I’m looking forward to seeing this comet, even though I’ll need to walk up a nearby hill before dawn.

    2. Bob KingBob King Post author

      As per what Anthony wrote, if you click on the large vertical map, you’ll go to a nice, beefy B&W pdf file you can print out to use at the telescope.

  2. Brad Young

    Saw a glimpse (70% certainty) this morning from Tulsa at 12:20 UT with 20 x 80 binocs on bridge near house. Right at chart position, about 6-7 degrees above horizon. Star BSC 5332 (mag 5.4) and BSC 5301 (mag 4.9) clearly visible. Conditions excellent clarity, avg seeing, with stiff N breeze. Could not have been brighter than 6th mag, no tail, only non stellar tiny haze barely brighter than twilight. Hopefully, I underestimated it or it will brighten as it comes up out of the dawn.

    Brad Young

  3. SNH

    Another good article Bob King. I was able to spot Catalina without a whole lot of trouble in my handheld 8×56 binoculars right at the start of astronomical twilight on the 22nd. It was only about 4 degrees above the eastern horizon and showing only a nearly stellar core. With a nearby star being a tad brighter, I placed the comet at about magnitude +6.8 (that’s with atmospheric extinction). I hope that it will continue to get better and better because it certainly didn’t look comet-like!

    1. Bob KingBob King Post author

      Thanks SNH and we appreciate you sharing your observation. Sounds like you got a better view than I. I was out that same morning with 7×50 binoculars and saw the comet only faintly about 3 degrees high. Your mag estimate is in line with others I’ve seen, though a few observers are reporting +6.1.

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