SN 2005gy

SN 2006gy was an extremely energetic supernova, sometimes referred to as a hypernova or quark-nova,[2] that was discovered on September 18, 2006. It was first observed by Robert Quimby and P. Mondol,[1][3] and then studied by several teams of astronomers using facilities that included the Chandra, Lick, and Keck Observatories.[4][5] On May 7, 2007, NASA and several of the astronomers announced the first detailed analyses of the supernova, describing it as the "brightest stellar explosion ever recorded".[6] In October 2007 Quimby announced that SN 2005ap had broken SN 2006gy's record as the brightest ever recorded supernova.[7] Time magazine listed the discovery of SN 2006gy as third in its Top 10 Scientific Discoveries for 2007.[8]

Characteristics
NASA artist's impression of the explosion of SN 2006gy.

SN 2006gy occurred in a distant galaxy (NGC 1260), approximately 238 million[citation needed] light years (72 megaparsecs) away. Therefore, due to the time it took light from the supernova to reach Earth, the event occurred about 238 million years ago. Preliminary indications are that it was an unusually high-energy supernova of a very large star, around 150 solar masses (M⊙), possibly of a type referred to as a pair-instability supernova. The kinetic energy released by the explosion has been estimated at 1052 ergs (1045 J)[5].
This diagram illustrates the pair production process that astronomers think triggered the explosion in SN 2006gy. A sufficiently massive star can produce gamma rays of such high energy that some of the photons convert into pairs of electrons and positrons causing a runaway reaction which destroys the star.

A pair instability supernova can only happen in stars that are very massive— having a range of around 130 to 250 solar masses. At a certain point in such a massive star's life its core begins to produce high energy gamma rays which have a greater energy than the rest mass of two electrons (mass-energy equivalence). These high energy gamma rays strike atomic nuclei and are converted from energy (or heat) to matter, disrupting the equilibrium between thermodynamic pressure and gravity in the star's core. The sudden drop in thermodynamic pressure causes the core to collapse. As the core collapses it gets hotter and hotter until a runaway thermonuclear reaction begins. In a few seconds, all of the fuel in the core undergoes a cataclysmic thermonuclear fusion, blowing the star completely apart while leaving nothing behind. [9]
Light curve of SN 2006gy (uppermost intermittent squares) compared with other types of supernovae.

Although the SN 2006gy supernova was intrinsically about one hundred times as luminous as SN 1987A, which was bright enough to be seen by the naked eye, SN 2006gy was more than 1,400 times as far away as SN 1987A, and too far away to be seen without a telescope.[10]

Denis Leahy and Rachid Ouyed, Canadian scientists from the University of Calgary have proposed that SN 2006gy was the birth of a quark star[11].

Another possibility is that SN 2006gy is not actually a pair-instability supernova but instead is powered by interaction with a dense circumstellar medium – a Type IIn supernova.[12].
Similarity to Eta Carinæ

Eta Carinæ (η Carinæ or η Car) is a highly luminous hypergiant star located approximately 7,500 light years from Earth in the Milky Way galaxy. Since Eta Carinæ is 32,000 times closer than SN2006gy, the light from it will be about a billion-fold brighter. It is estimated to be similar in size to the star which became SN2006gy. Dave Pooley, one of the discoverers of SN2006gy, says that if Eta Carinæ exploded in a similar fashion, it would be bright enough that one could read by its light here on Earth nights, and would even be visible during the day time. SN2006gy's Apparent magnitude (m) is 15,[1] so a similar event at Eta Carinæ will have an m of about -7.5. According to astrophysicist Mario Livio, this could happen at any time, but the risk to life on Earth would be low.[13]
References

^ a b c d "List of Supernovae". Retrieved 2011-01-08.
^ Superluminous Supernovae SN2006gy, SN2005gj and SN2005ap: Signs for a New Explosion Mechanism
^ IAU Circular No. 8754, accessed May 8, 2007
^ SN 2006gy: An extremely luminous supernova in the galaxy NGC 1260 Ofek et al., Accessed May 8 2007, arxiv.org
^ a b Discovery of the most luminous supernova ever recorded, powered by the death of an extremely massive star like Eta Carinae, Smith et al. (PDF)
^ NASA's Chandra Sees Brightest Supernova Ever, NASA Press Release on the Discovery, May 7, 2007
^ "Enigmatic supernova smashes brightness record", New Scientist, October 12, 2007
^ "Top 10 Scientific Discoveries: #3. Brightest Supernova Recorded", Time, 2007
^ Pair Instability Supernovae and Hypernovae, Nicolay J. Hammer, 2003, accessed May 7, 2007
^ Universe Today:Chandra Sees the Brightest Supernova, accessed May 7, 2007 Archived May 10, 2007 at the Wayback Machine.
^ NewScientistSpace:Was the brightest supernova the birth of a quark star?, accessed August 21, 2007
^ Smith, N.; Chornock, R.; Silverman, J. M.; Filippenko, A. V.; Foley, R. J. (2010). "SPECTRAL EVOLUTION OF THE EXTRAORDINARY TYPE IIn SUPERNOVA 2006gy". The Astrophysical Journal 709: 856. Bibcode 2010ApJ...709..856S. doi:10.1088/0004-637X/709/2/856. edit
^ "Megastar explodes in brightest supernova ever seen". Reuters. 2007. Retrieved 2007-05-07.

SIMBAD data

External links
Astronomy Picture of the Day 10 May 2007
NASA's Chandra Sees Brightest Supernova Ever
Workshop on First Stars III website (upcoming conference, links to prior papers)
Giant exploding star outshines previous supernovas (CNN.com)
Space.com article on SN 2006gy.
Star dies in brightest supernova, BBC, Tuesday, 8 May 2007, 03:35 GMT
The Greatest Show in Space, Time magazine Thursday, May 21st, 2007 Pages 56-57
Supernova may offer new view of early universe
Lick Observatory Laser Guide Star Adaptive Optics
PAIRITEL (telescope) website
Image SN 2006gy

List of supernovae