NASA’s Chandra observatory, in unison with ground-based optical telescopes, has relased details of a supernova from last September which is the brightest ever recorded. SN 2006gy exploded in galaxy NGC 1260 and was the brightest such event ever seen. NGC 1260 is 240 million light years away and the supernoa appeared to outshine the entries galaxy in both optical and x-ray wavelengths.
This event is believed to be a Type II supernova, which occur at the end of a large stars life. When a star is larger than about nine solar masses it will go through a different set of fusion reactions at the end if its life. As the hydrogen runs out, having all been converted to other elements, the stars begins to grow unstable at its centre as the heavier elements grow more and more dense and the gravitational pressure becomes unsustainable by the star’s newlty formed iron core. When the core reaches a mass known as the Chandrasekhar limit, a catastrophic collapse ensues during which the stars outer layers fall inward at a speed nearly one quarter that of light.
In just a few seconds 1040 joules (one hundred billion trillion trillion trillion) of gravitational energy are crushing down on the core which becomes as desne as an atomic nuceus and so the collapse bounces. Bounce is a very gentle word for what happens but since the core has taken all the pressue it possible can, the falling material has no choice but to rebound and it blows outward, destroying the star with it and showering the universe in neutrinos and everything else.
In the above image, taken from NASA’s press release, the top section shows an artists impression of the event close-up. The lower left panel is an infrared image and the lower-right an x-ray image from Chandra. both the lower panels show the nucelus of NGC 1260 on the left and SN 2006gy on the right.
SN 2006gy is thought to be the largest such event witnessed and even more interestingly, it bore a striking resemblance to a star in our own galaxy just before it died. Eta Carinae was the star which appeared in Hubble’s 17th Anniversary image. SN 2006gy is thought to have beren a lot like ETa Carinae; both were enormous stars which had begun spewing out material. If Eta Carinae follows the same path as SN 2006gy then we could be in for more than just a bright light in Chandra’s field of view. Whereas SN 2006gy is 240 million light years away, Eta Carinae is only 7,500. If it did go supernova then it would be visible during the day and at night would cast shadows almost as well as the full moon.
Hopefully more information and more images will follow and with any luck Eta Carinae will give us a repeat, close-up discussion someday in the future. If it did then it would be the most fantastic event in all of modern civilisation.