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