How to Find the New Supernova!

by trg

This week, while the moon is still not overly bright, you have a chance to see a supernova. Unfortunately, this event is taking place not in our own galaxy — where it would be readily visible to the naked eye — but in the galaxy M101.

The supernova was first observed on Aug. 23 with the 48-inch Oschin Schmidt telescope at Palomar Mountain Observatory in California. First called PTF 11kly and now designated SN2011fe, the supernova was discovered shining at a magnitude of +17.2, but has been brightening rapidly ever since.

Within the next week, it might reach 11th magnitude — appearing to shine some 300 times brighter than when it was first seen (remember, the lower the figure of magnitude, the brighter the object). The threshold of naked-eye visibility is magnitude 6.5.

The galaxy in which this supernova is located, M101, has a linear diameter of more than 170,000 light-years, making it among the biggest disk galaxies known. And it is located at a distance of about 24 million light-years, meaning that the explosion actually took place 24 million years ago. It’s taken that long for the light to get to us.

How can you find it? Easy. It’s at a very convenient location, forming an equilateral triangle with the two end stars of the Big Dipper’s handle, in the direction away from the Dipper’s bowl. It’s just 5 degrees east from the double star in the middle of the handle of the Big Dipper, and about the same distance east-northeast from the star that marks the end of the handle. Remember that your clenched fist held at arm’s length measures roughly 10 degrees.

As darkness falls this week, the Big Dipper can be seen about halfway up in the northwest sky, with its handle pointing upward. By around 3 a.m. local daylight time, the handle is very low above the northern horizon. So if you want to see M101, your best bet is to try looking during the early evening hours while it’s still reasonably high in the sky.

M101′s magnitude is listed as +7.7, which is only about three times dimmer than the threshold of naked-eye visibility. But while it may seem that this galaxy would be relatively easy to see in a telescope or even binoculars, it should be stressed that it’s a rather challenging object to spot because of its great size and relatively low surface brightness. It is best seen under a very dark sky.

Inexperienced observers should be careful not to use too high a magnification with their telescopes. Faint and extended luminous objects are often evident only because of their contrast against the sky background.

The arrow marks the location of PTF11kly in images taken at the Palomar Observatory the nights of Aug 22,23, and 24. Credit Peter Nugent and the Palomar Transient Factory.

The supernova is located in the southwest (lower left) quadrant of M101. If you can find the galaxy’s hazy patch, you just might also be able to discern the supernova as a tiny starlike speck of light within that area.

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