This is the big week so many of us in the northern hemisphere have been waiting for. Comet C/2011 L4 PANSTARRS, which has put on a splendid show in the southern hemisphere, finally comes to a sky near you.
Sky watchers in Australia report it looks like a fuzzy star as bright as those in the Big Dipper with a short stub of a tail visible to the naked eye. The comet should brighten further as it wings its way sunward. Closest approach to the sun happens on March 10 at a distance of 28 million miles or about 8 million miles closer than the planet Mercury.
If you live near the equator you can already hunt for PANSTARRS. It will be out tonight March 4 very low in the west-southwest sky 25 minutes after sundown. Depending on your latitude, the comet will make its first appearance over the U.S. March 6-8 assuming the sky at your location is transparent and haze-free.
As described in an earlier blog, PANSTARRS’ low altitude presents a few challenges. Approaching clouds and general haziness near the horizon can make it a tricky to find. The maps should help as will a pair of binoculars. Use them to sweep just above the western horizon later this week to find the comet.
As the nights pass, PANSTARRS rises higher in the sky and becomes easier to spot for northern hemisphere observers while disappearing from view in the south. On the 12th, a thin lunar crescent will shine just to the right of the comet. Not only will it make finding this fuzzy visitor easy-peasy, but you’ll have the opportunity to make a beautiful photograph.
The maps shows the arc of the comet across the western sky in the coming two weeks for three different latitudes. Along the bottom of each map is the comet’s altitude in degrees for the four labeled dates. The sun, which is below the horizon, but whose bright glow you’ll see above its setting point, will help you determine exactly in what direction to look.
A word about altitude. Astronomers measure it in degrees. One degree is the width of your little finger held at arm’s length against the sky. Believe it or not, this covers two full moon’s worth of sky. Three fingers at arm’s length equals 5 degrees or the separation between the two stars at the end of the bowl of the Big Dipper. A fist is 10 degrees.
To find PANSTARRS, locate it on the map for a particular date, note its approximate altitude and relation to where the sun set and look in that direction. Assuming your sky to the west is wide open and clear, you should see a comet staring back. If not, sweep back and forth in the area with binoculars. Sound good? Great – now have at it!