Sunday, February 6, 2011

Supernova underway in NGC-2655

Last night I had the rare chance to observe the aftermath of one of the most powerful explosions the Universe ever sees, the total destruction of a star from a supernova explosion. Stars explode as supernovae all the time in galaxies other than our own, but most are very faint and at best are visible through large amatuer telescopes, if not large professional telescopes only. However, on occassion one goes off in a nearby galaxy and become easily visible in modest amateur telescope, or even binoculars. Such was the case with supernova SN2011b, a type IA supernova that occured in the spiral galaxy NGC-2655, which is in the constellation Camelopardalis the giraffe. Type 1A supernovae occur when a white dwarf gathers so much matter from another star that mutal repulsion between electrons can no longer support it against it's own gravity. These do not occur only in star forming regions within spiral and irregular galaxies, they go off in all galaxies and even globular clusters. White dwarfs that explode as supernovae are not young stars, they are usually hundreds of millions if not billions of years old before they finally reach the tipping point. The star's core collapses, runaway carbon and oxygen fusion starts, then the entire star blows apart in a blast that outshines all the other stars in the host galaxy put together. The violent shockwaves that are started often take the outer envelope of the other star with them as the wreckage is hurled into space at speeds of 10,000 kilometers a second or more. In the fury of the runaway nuclear fusion that consumes the entire star which acts like a nuclear reactor out of control, the carbon and oxygen gets turned into everything from sodium to iron and nickel. Radioactive decay is making the supernova shine at about 13th magnitude,  and thus visible in an 8 or 10-inch telescope. It peaked at magnitude 12.8, and now it's fading as the radioactive nickel-56 generated in the blast decays into stable iron-56. Currently SN2011b shines at magnitude 13.1, but soon it will fade enough to be out of reach of most amateur telescopes. It will of course remain in the grasp of CCD cameras for much longer.

Other objects examined last night included the interacting galaxy pair NGC-1531 and 1532 in the constellation Eridanus, the river. NGC-1532 is a large nearly edge-on spiral galaxy that is drawing in the much smaller elliptical galaxy NGC-1531. At a magnitude of 10.6, it's bright enough but is low in the sky even from the Alabama Gulf Coast. NGC-1531 is much dimmer and harder to see, but averted vision reveals the magnitude 12.3 galaxy at 188X.

Another galaxy I observed was the diminutive spiral galaxy NGC-691 in Aires. Nestled among a group of foreground stars, this small galaxy was only visible as a round glow with a brighter core.
Two more galaxies in Pisces the fishes also were observed, NGC-718 and NGC-741. NGC-718  was the brighter of the two, with an oval outline and a brighter core. It's a barred spiral galaxy that was quite easy to locate and is moderately bright.

NGC-741 is a dimmer elliptical galaxy that has a smaller companion near it, NGC-742. Small and round with a brighter core, NGC-741 was barely visible even though it's magnitude was 11.6. The sky conditions might be why that was the case, because fog and frost was forming everywhere at the landing strip by nine p.m. The smaller companion galaxy NGC-742 was not visible, not that at a magnitude of 14.4 would it be visible through a 10-inch telescope from a light polluted site.
Although the fogging up of my eyepieces and the sky becomming very milky cut short observing last night, it was well worth the trip to the airstrip to observe these galaxies as well as favorites such as the Double Cluster, Crab Nebula and the Messier galaxies M-31, M-32 and M-74.


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