See Comet PanSTARRS This Week

Hey Space Placers!

This week the western sky has a visitor from the deep depths of the outer solar system - Comet PanSTARRS. March 12-18 is prime time to view the comet as after this week it will start to fade. Officially known as Comet C/2011 L4 in order to distinguish it from the other comets discovered by the automated sky survey observatory Pan-STARRS http://pan-starrs.ifa.hawaii.edu/public/home.html
in Hawaii, the comet will finally be visible to observers in the Northern Hemisphere. 

Comets http://solarsystem.nasa.gov/planets/profile.cfm?Object=Comets
are named after their discoverers so Pan-STARRS gets the credit for finding this icy interloper from the outer solar system in June 2011. 

Comets are best described as dirty snowballs as they are frozen leftovers from the formation of our solar system 4.6 billion years ago. They are thought to have a rocky or rubble pile center a couple of kilometers in diameter known as the nucleus that is covered with frozen water and gases. 

Over a trillion comets are thought to form the Oort Cloud http://solarsystem.nasa.gov/planets/profile.cfm?Object=KBOs&Display=OverviewLong
a vast spherical reservoir of comets very distant from the Sun. A passing molecular cloud, a collision with another cometary body or other gravitational encounters can cause a cometary body to begin its long fall into the inner solar system. Comets such as these and PanSTARRS pass through the solar system only once and are known as long period comets.

Another reservoir of comets lies out in the area of Pluto and are known as short period comets. These comets can become regular visitors to the inner solar system with “Halley’s Comet”   https://www.astrosociety.org/edu/publications/tnl/01/01.html  being the most famous of our time.   

When a comet passes through the inner solar system the surface of the nucleus gets heated by the Sun which causes the water, gases and dust to form an atmosphere around the comet called the coma. The coma can grow in size to hundreds or thousands of kilometers in size. Solar wind and pressure from sunlight act upon the coma and can cause a tail to form flowing from the comet. These tails can be grand in their size and scope, sweeping across whole sections of the sky and be quite spectacular. 

You may recall seeing Comet Hyakutake in 1996 and Comet Hale-Bopp in 1997. These comets were wonderful and awe inspiring to see and had decidedly different and distinct tails. Comet PanSTARRS has a reported tail but it is rather small in the sky due to the large distance from us.

Comet PanSTARRS has been visible for observers down under for a few weeks now and has been spotted fairly easily in their western sky in twilight sporting a short but visible tail. The comet is over 105 million miles from Earth which is farther than the distance to the Sun and is pretty far when it comes to encounters with comets that can be seen.

To see the comet this week you need to have a clear western horizon that is free of trees, bright lights and buildings. You will likely need binoculars as well to find the comet which may be visible to your unaided eye once you have found it. The thin crescent Moon will be a guidepost to see the comet on March 12th and 13th as you can see in the accompanying diagram. 

Start looking 30-45 minutes after sunset. Slowly scan the sky with binoculars or your eyes. Comet PanSTARRS will look like a fuzzy star with a short tail. If you have a camera and tripod try taking some pictures of the comet. It truly will be a once in a lifetime shot. Read more about Comet PanSTARRS http://www.skyandtelescope.com/community/skyblog/observingblog/Spot-Comet-PanSTARRS-in-Twilight-196688441.html

I hope you will see this piece of solar system history. Your experience in hunting down Comet PanSTARRS will prove useful as in the fall we will be witnesses to what may be an historic flyby of Comet ISON
  http://science.nasa.gov/science-news/science-at-nasa/2013/18jan_cometison/. Some are speculating that this will be THE comet of the 21st century. We’ll have to wait on that claim to see how Comet ISON develops - it could be spectacular as a sight to behold or a dud to be forgotten. 

Look for Comet PanSTARRS low in the west in twilight. Don't expect it to appear as obvious as shown here.This chart is drawn for viewers in the world's mid-northern latitudes (U.S., Canada, Europe except far north, China, Korea, Japan). Feel free to reprint it, but include the credit line Sky & Telescope magazine, and online use must include a link to SkyandTelescope.com . Click for high quality version.

Sky & Telescope diagram

Good Hunting!

Sky Guy in VA