Astro Bob A look at celestial happenings in the Northland and beyond Bob King View my profile Click here to view previous posts or additional resources

A very nice morning sky comet

Look northeast around the start of dawn to see Comet McNaught. For Duluth and vicinity that would be 2:30-3 a.m. In the coming week, it's one-and-a-half "Cassiopeia lengths" below the left side of the famous W. Tomorrow morning you can also use Gamma in Andromeda to help you find it. On the 13th and 14th, the comet passes not far below Alpha Persei. Created with Chris Marriott's SkyMap software

I tried, I tried. Last night the sky was so clear the stars seemed especially close. I set up the telescope and poked around a little then went to bed in anticipation of seeing Comet C/2009 R1 McNaught at the start of dawn. Nights are so short now in the northern states, that if you opt to observe in the evening you'll soon discover you only have an hour left till dawn.

I awoke at 2:15 a.m. in a woozy, half-conscious state and peered out the front window. Time for a look at that comet, right? Forget it. The sky was overcast, and after a half-hour of lost sleep divining cloud patterns, I returned to bed. Darn! The joys of astronomy. Hopefully the sky will clear soon - this is a comet not to miss.

A beautiful wide-angle shot of Comet McNaught taken on June 6 at dawn. The time exposure shows the bright coma or head and long, skinny tail made of carbon monoxide gas fluorescing in sunlight. The orange star at top left is Gamma Andromedae. Credit: Michael Jaeger

Robert McNaught discovered his comet from Siding Spring Observatory in Australia as a faint blip of light on a CCD camera last September. This is the same McNaught who first spotted the Great Comet of 2007 that became visible in daylight and put on a magnificent show for southern hemisphere observers in the winter of that year.

His current fuzzball is now at its best and brightest in the morning sky as it travels from Andromeda through Perseus and into Auriga over the next two weeks. To see it, you'll need to surmount two challenges: the early hour and its low elevation. Comet McNaught is best seen during a brief window from around 2 a.m. until it fades away in dawn's light. Around here that's about 3:30. Secondly, the comet is very low in the northeastern sky so you'll need a good, open view in that direction. For viewers in mid-northern latitudes the comet will only get as high as two outstretched fists (15-20 degrees) above the horizon at best.

If you live in the northern U.S. and southern Canada, McNaught becomes a circumpolar object starting Wednesday; it never sets and remains visible during both evening and morning. With one caveat. The comet will only be a few degrees above the northern horizon during evening hours. Until June 23, the best time for spotting it will still be just before and at the start of dawn.

McNaught has steadily brightened since its discovery and now stands at magnitude 5.4, right around the limit for naked eye viewing. As comets go, that's bright, and it's easily visible in binoculars as a small patch of concentrated, fuzzy light. What you'll see is the comet's head or coma and perhaps a stub of a tail pointing upward. Inside the coma, a telescope will show a tiny bright spot called the nucleus. The westward-pointing tail should be more obvious than through binoculars.

A closeup of the comet shows streamers in the tail created when cometary gases interact with the solar wind. The comet's head or coma glows green from cyanogen gas. Credit: Michael Jaeger

Deep within the nucleus and invisible in almost all telescopes is the comet itself, an irregular shaped body maybe a mile or two across composed of ice and dust. Astronomers call them icy dustballs. When a comet like McNaught enters the inner solar system, the sun's heat causes the ice to vaporize and carry the dust along with it, giving the newly-formed head a fuzzy or soft appearance. Pressure and radiation from sunlight push the material into a tail. Depending on the speed and direction of the sun's "wind" of particles called the solar wind, tails grow and linger or snap off like a lizard's and grow again. McNaught lost its tail last week and grew a new one in just a couple days.

Mars and Regulus together make a striking duo in last night's western sky. If you missed them, they'll be out again tonight, not quite as close, but close enough. Details: 35mm lens at f/2.8, ISO 800 and 30-second exposure. Photo: Bob King

I promise you I'll be out looking for the comet again as soon as weather allows. I hope you will be, too. McNaught jumped nearly a full magnitude in the past few days and should continue to brighten as it makes it closest approach to the sun early next month. Good luck and happy comet hunting!

Posted by: rking@duluthnews.com on 6/7/2010 at 9:29 AM | Comments (0) | Permalink | Edit

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