The nearest supernova of its type to be discovered for more than 40 years is expected to reach its maximum brightness around the 8th and 9th of September 2011.

The supernova (named PTF11kly) was discovered by British astronomers on the 24th August 2011 using the famous 48-inch Schmidt telescope at Mount Palomar. Operating the telescope remotely they found a "new" 17th mag. star lying within one of the spiral arms of M101 in Ursa Major. It has now brightened significantly and as of the 8th September the supernova hovers around magnitude 10, which is bright enough to be seen with an 80mm (3.1 inch) telescope under dark skies or even with good binoculars.

Discovery image of supernova PTF11kly (Peter Nugent/PTF collaboration)

But here comes the warning, although M101 has a relatively bright mag of +7.9, it is orientated almost exactly face on to Earth. As a result it has a low surface brightness and is therefore much more difficult to observe than its magnitude suggests. Even with just a small amount of light pollution, M101 is a notoriously difficult object to locate. This is especially true for binocular and small telescope observers and such is the case that it is often not even included in some beginners observing guides. So unless you live under exceptional dark skies, well away from any light pollution, spotting M101 and its supernova with a small instrument will be challenging if not impossible.

The chart below shows how to find M101. It is easy to locate the general area where M101 lies as it forms one corner of a triangle with well-known Plough stars Mizar and Alkaid.

M101 Supernova Star Chart

M101 Supernova Star Chart - pdf format

PTF11kly is located 22 Million light-years from Earth and the spectrum suggests it to be a Type 1a supernova, which occurs when a white dwarf star in a binary system explodes. For comparison, Tycho's Supernova of 1572 was of the same type and supernova 1987a in the Large Magellanic Cloud was of the much rarer Type II-P.

M101 Data

ConstellationUrsa Major
Type Spiral Galaxy SAB(rs)cd
RA (J2000)14h 03m 12s
DEC (J2000)+54d 20m 55s
Apparent Dimensions 29' × 27'
Apparent Magnitude7.9
Distance (light-years)22 Million
Diameter (light-years)180,000

M101 Supernova Data

RA14h 03m 5.81s
Dec+54h 16m 25.4s

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