Pinwheel Galaxy's SN2011FE supernova causes stir
Brian Vastag, Washington Post
Monday, September 5, 2011

Twenty-one million years ago in the Pinwheel Galaxy - an elegant, spiral-armed neighbor of our own Milky Way - an old, dim star had a very bad day. It exploded and began to blaze like a billion suns.
On Aug. 24, Peter Nugent had a very good day. The Lawrence Berkeley National Laboratory astrophysicist was about to grab lunch when he checked to see if a robotic telescope had spied anything of interest the night before. Bingo. Boom. Supernova.
And not just any supernova. Every night, astronomers spot several exploding stars across the universe. But this one was so close - in cosmic terms - and seen so soon after its light reached Earth that astronomers are calling it the supernova of a generation.
An automated sky survey that searches for new nighttime objects with a telescope at the Palomar Observatory in San Diego County first flagged the supernova.
Soon, telescopes around the world - and beyond, including the Hubble Space Telescope - swiveled to take a peek.
"This is a special event," said Ken Sembach of the Space Telescope Science Institute in Baltimore. "Everyone wants a piece of it."
Nugent said the blaze will continue to brighten until Wednesday or Thursday, visible just above the handle of the Big Dipper to backyard astronomers wielding binoculars.
The last supernova to generate such buzz flared into view in 1972. Before that, a 1937 explosion caught everyone's attention.
Three hours after Nugent's discovery, the Grand Canary Telescope off the coast of Africa - where the sun had just set - took a look. The jackpot grew bigger when that scope's data poured in. The Pinwheel supernova - technically known as SN2011FE - was a Type 1a, of special interest to astronomers.
Type 1a's all blaze with nearly the same brightness. That makes them the perfect yardsticks for measuring cosmic distances. Their apparent brightness tells us how far away they are.
In the 1990s, Robert Kirshner, a veteran Harvard University supernova hunter, led a team that leveraged this property to make one of the biggest discoveries of the past century: The universe is flying apart, rapidly accelerating.
To explain this, cosmologists were forced into an uncomfortable conclusion. Either gravity does not work the way it is supposed to, or a mysterious force is pushing galaxies apart at a quickening pace. They called this unknown force "dark energy" and still have little idea what it is, even though they are able to calculate that it constitutes an astounding 73 percent of all mass and energy in the universe.
Cosmologists hope the new supernova will help refine estimates of the universe's acceleration. The data might even hint at the nature of dark energy.

More Technical Description below:

Supernova Erupts in Pinwheel Galaxy


The supernova was up to magnitude 13.8 on The American evening of August 25th and 12.4 on The evening of The 27th. by The evening of The 29th it was up to 11.5 and easier to spot than The galaxy itself in moderately light-polluted skies. On The evening of The 30th, S&T's Tony Flanders put it at 11.2. On The evening of September 4th it was around 10.3 and still brightening, though much less fast now.


Good news for those of you who missed out on
June's supernova in The Whirlpool Galaxy, M51: You can slew just across to The other side of The Big Dipper's handle to track another stellar explosion.

Supernova in M101, August 22-24
Supernova PTF 11kly brightens up from nothing in images taken with The 48-inch (1.2-m) Schmidt telescope at Palomar Observatory on The nights of August 22쭯24. Click here for larger views of The individual images. Peter Nugent / Palomar Transient Factory
This one's located in The face-on spiral M101, The Pinwheel Galaxy. It was discovered on August 24th at magnitude 17.2 by The Palomar Transient Factory (PTF), an automated supernova search being conducted with The 1.2-m Oschin Schmidt Telescope at Palomar Observatory in southern California.

Since The same telescope saw nothing at The same location one day earlier (limiting magnitude = 20.6), The stellar explosion must have been caught mere hours after its onset. According to PTF participant Andy Howell (University of California, Santa Barbara),
never before has a Type Ia supernova been discovered so early in its brightening. "As soon as I saw The discovery image I knew we were onto something big," he says.

Designated SN 2011fe (though dubbed "PTF 11kly" initially), The supernova is brightening rapidly. It had already climbed to 13.8 by 20h Universal Time on August 25th, as noted by KrisztiÐn SÐrneczky at Konkoly Observatory in Hungary. Spectra taken earlier that day at Lick Observatory show broad, blueshifted absorption lines from ionized calcium and silicon blasting outward at 14,500 to 16,500 km per second ― and no hydrogen lines. These are characteristics of a
Type Ia supernova: The complete thermonuclear destruction of a carbon-oxygen white dwarf star that had been collecting mass in a binary system.

The supernova was up to magnitude 13.8 on The American evening of The 25th and 12.4 on The evening of The 27th. S&T's Alan MacRobert estimated it at 11.5 on The American evening of The 29th (August 30.1 UT) using a 12.5-inch scope at 75≠ and an AAVSO comparison-star chart. by The evening of September 4th it was magnitude 10.3 by AAVSO measurements.

Supernova in M101
Early on August 25th Universal Time, Australian observer Joseph Brimacombe used a robotic 20-inch telescope at New Mexico Skies to record The brightening supernova in an outer arm of The Pinwheel Galaxy, Messier 101. North is up and east to The left. Click here for a larger view. Joseph Brimacombe

The early detection, combined with The relative closeness of M101 (23 million light-years), makes this a spectacular find for professional researchers. A normal Type Ia supernova at this distance should reach magnitude 10.0 at its peak, if none of its light is absorbed by interstellar matter in M101. That's well within visual reach in a 4-inch telescope ― and much brighter than The galaxy appears visually! In a light-polluted sky you'll be using The supernova to find The galaxy rather than vice versa.

If you haven't yet tracked down this fleeting fireball, do it soon. The Dipper's handle is getting lower after dark, and moonlight will return to The evening sky by about September 3rd or 4th.

Relatively bright at 8th magnitude but large and diffuse, The Pinwheel Galaxy sits north of The last two stars in The Big Dipper's handle, forming a roughly equilateral triangle with them 6▲ on a side. The supernova is located about 4.4 arcminutes south (and a bit west) of M101's center at right ascension 14h 03m 05.8s, declination +54▲ 16▽ 25▼. Click
here for a finder chart.

Here's The American Association of Variable Star Observers'
Special Alert that went out August 24th with a link to comparison-star charts and other observing info.

Here's a
light curve of magnitude measurements (visual, R, V, and B) that The AAVSO has received.

Posted by Kelly Beatty, August 25, 2011
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