Catch a falling star

Tom Feilden
Science correspondent, Today

Image source, Other
Image caption,
Supernova PTF11kly will be easily visible for just a few days

If you're the owner of a decent pair of binoculars train them on the handle of The Plough or Big Dipper a little after twilight tonight.

Weather permitting (and admittedly that's a big if) you could be in for something of a surprise as a single bright white dot has been added to this most familiar of astronomical constellations.

The result of a massive explosion some 21 million light years away in the Pinwheel Galaxy M101, the nearest supernova of its type to be discovered for 40 years should be at its brightest tonight.

Supernovae occur when stars reach the end of their life, collapsing in on themselves and triggering an explosion that can briefly outshine an entire galaxy, before fading away over a period of weeks or months.

This one was spotted by scientists from Oxford University and the Palomar Transient Factory collaboration on 24 August.

"The best view of this exploding star is likely to be on Thursday," says Dr Mark Sullivan who led the team.

"Whilst it looks more or less like just another bright star, unlike its companions this supernova will soon fade away, and after a few days it will only be visible with larger telescopes".

The discovery of this exploding star (somewhat prosaically named PTF11kly) is particularly exciting because it's a type 1a supernova - the kind used as "standard candles" by astronomers to measure distances and the expansion of the universe.

The last time one occurred so close was 1972. Before that you have to go back to 1937, 1898 and 1572.

"For many people it could be a once in a lifetime chance to see a supernova of this kind blossom and then fade before their eyes," says Dr Sullivan.

"We may not see another one like it for another 40 years, or perhaps over 100 years".

And if you are lucky enough to catch a glimpse of PTF11kly through a break in the clouds you'll be in good company. Both the Hubble Space Telescope and the giant Keck telescopes at Mauna Kea in Hawaii will be zeroing in on this cosmic firework display as it waxes and wanes.

The supernova's early detection, combined with its relative proximity, has presented scientists with a rare opportunity to study its development in greater detail.

Finding PTF11kly is fairly straightforward.

Look directly between the first two stars in the handle of the Plough (Alkaid and Mizar), then move upwards until you reach the apex of an imaginary equilateral triangle.

You are looking at the Pinwheel Galaxy M101, and with a good pair of binoculars, the supernova should be clearly visible as a bright white star.