An exploding star has suddenly appeared in the night sky, dazzling astronomers who haven't seen a new supernova so close to our solar system in more than 20 years.

In just the last few days, a the supernova emerged as a bright light in Messier 82 - also known as the Cigar Galaxy - about 12 million light-years away in the constellation Ursa Major, or the Great Bear. The supernova, which one astronomer described as a potential "Holy Grail" for scientists, was first discovered by students at the University College London.

Positioned between the Big Dipper and the Little Dipper, the new supernova should be easy for skywatchers in the Northern Hemisphere to spot; it may even brighten enough to be visible through a small pair of binoculars, said astronomer Brad Tucker, of the Australian National University and the University of California, Berkeley. [Supernova Photos: Great Images of Star Explosions]

New supernova in the sky

But beyond creating a skywatching spectacle, the cosmic event also affords astronomers a rare opportunity to study an object that might help them understand dark energy.

The supernova was first observed Tuesday (Jan. 21) at 7:20 p.m. local time (19:20 UTC) by a group of students led by Steve Fossey at the University College London. (The comparison image to the right shows the supernova suddenly appearing in M82). The object may be the nearest supernova to be observed since the intense Supernova 1987A was spotted in February 1987 in the Large Magellanic Cloud, a dwarf galaxy companion of the Milky Way about 168,000 light-years from Earth, according to UCL.

"It was a surreal and exciting experience taking images of the unidentified object as Steve ran around the observatory verifying the result," UCL student Guy Pollack said in a statement.

Astronomers from Caltech have confirmed the supernova and classified it as a young, reddened Type Ia supernova. These kinds of objects are thought to originate in a close binary system where at least one star is a white dwarf, or a small, dense core of a star that has ceased undergoing nuclear reactions. If the white dwarf siphons off too much mass from its companion star, a runaway nuclear reaction begins inside the dead star, leading to a brilliant supernova

Because Type Ia supernovas are believed to shine with equal brightness at their peaks, they are used as "standard candles" to measure distances across the universe. In fact, careful measurement of Ia supernovas led to the Nobel Prize-winning discovery that the expansion of the universe is actually accelerating.

A supernova "Holy Grail"

But in order to learn more about the cause of the acceleration (what scientists call dark energy), Tucker said astronomers need more precise measurements.

"The two large problems with using Ia for distance measurements, are the progenitors, what the star that explodes actually is, and how dust affects these measurements," Tucker explained in an email. "So the fact that this [supernova] is a Type Ia, caught young, means we have a good chance of finding clues to the explosion."

The Hubble Space Telescope also captured detailed images of the Cigar Galaxy from before the star would have blown up, which means astronomers might be able to directly see the star in past observations, Tucker explained.

What's more, this is a "reddened" supernova, meaning it occurred a dusty environment.

"By knowing there is lots of dust, we can analyze out how the dust is impacting the colors of the [supernova] and therefore the distance measurements, and use this to calibrate other [supernovas]," Tucker said in an email. "In short, this is the Holy Grail."

The International Astronomical Union's Central Bureau for Astronomical Telegrams has listed some of the supernova sightings under the temporary designation PSN J09554214+6940260, starting with a Jan. 22 observation by a group of amateur astronomers in Russia.

Images from the supernova-hunting KAIT robotic telescope at the Lick Observatory in California confirm the object was not present as recently as 15 January, meaning the supernova is a few days old, Tucker said.

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