What may be the brightest comet of the year is currently making a sweep across the evening sky. Before you get too excited, the object, named C/2018 Y1 Iwamoto, is only bright relative to the other comets we’re expecting this year. None of those are predicted to breach the naked-eye limit and it’s unlikely C/2018 Y1 will either. In truth, we’re talking another fuzzball similar to 46P/Wirtanen that passed by the Seven Sisters cluster last December. Just like that comet, this one is also visible in binoculars.
I like fuzzballs just fine and hope you will too. While we’re due for a comet to make us cower like the ones depicted in woodcuts from the Middle Ages, none are on the radar. Our last knock-your-socks-off cometary visitor was Hale-Bopp in 1997.
Japanese amateur Masayuki Iwamoto discovered the object on images taken December 18 last year. It has since brightened and moved from low in the morning sky to a more convenient altitude in the evening sky. I pulled into a dark, off-road spot Sunday night and found the comet in 10×50 binoculars in the constellation Virgo. It wasn’t particularly bright, but I had no trouble seeing it — a small, softly-glowing hazy spot about two-thirds the size of the full moon.
Through a 10-inch telescope at 57x it was a giant blob with a faint aqua tinge like it had just stepped out of the Caribbean. The blob part is called a coma, and Iwamoto’s coma became denser as my gaze worked its way from edge to core. Other observers have reported seeing a short tail pointing to the northwest but as hard as I tried I couldn’t make it out.
C/2018 Y1 is currently magnitude 7, definitely within binocular range from a dark, non-light polluted sky. I suspect you’d see it in the outer suburbs of a medium-sized city as well, but it’s very diffuse, making the object a tough catch from a city.
Here’s the good news. Iwamoto passes closest to the sun today (Feb. 6) and will buzz just 28 million miles from the Earth on Feb. 12, growing a little brighter over the coming week. It also climbs quickly in altitude. Right now, you have to wait until 10:30-11 p.m. local time for it rise high enough for a good look. But by Sunday (Feb. 10), it’s already some 25° (2.5 “fists”) by 9 p.m. and just keeps getting higher after that.
When near the Earth it will appear to move fast, covering 7.5° per day on Feb. 10-11. Even a small telescope will show the comet creeping along through the star field at the rate of nearly one-and-a-half “full moons” every 90 minutes. To find Comet Iwamoto use the map provided which shows the sky facing east-southeast around 10:30 p.m. Central Time. For the next few nights, the comet won’t be close to any bright stars but will soon cross into Leo the lion, a constellation with some easy sky-marks. From Feb. 9-12 you’ll find Iwamoto near or within the bright asterism called the Sickle of Leo, which also looks like a backwards question mark.
Catch the comet soon before the moon scuttles your dark skies. It’s a crescent now but waxing toward half (Feb. 12), so we have till about next Wednesday for good views unless you go out late after moonset. For more details including a very special conjunction the comet will have with a bright galaxy, please see my additional article and map in Sky and Telescope.
Crossing my fingers you’ll all be able to see this tuft of cosmic fluff.