Friday, June 22, 2012

NGC galaxies and a supernova

Last weekend after a period of cloudy weather and moonlit nights, it was finally possible to observe my favorite objects, galaxies and nebulae. Wasting no time, I brought both the 10 and 15-inch Dob to the airstrip with the goal of finding the supernova SN2012cg and to draw Virgo and Coma Berenice's galaxies. SN2012cg is underway right now in the Virgo galaxy NGC-4424 and is plainly visible in the nuclear bulge. It is definitely a type 1A event, which can occur anywhere in all galaxies as well as globular clusters. What causes them is matter streaming from a normal star to a nearby white dwarf, a dead and collapsed star that no longer generated internal energy by nuclear fusion. Only electrons mutual aversion to each other supports the star against further collapse, and left to itself a white dwarf can last almost forever. If hydrogen gas rains down onto the dwarf at a high rate, it starts to fuse into helium at a steady rate on the surface instead of building up until it all ignites and gets blasted off the star during a nova outburst. This increases the mass of the white dwarf until mutual repulsion between electrons can no longer oppose the star's own gravity. The star immediately collapses, runaway nuclear fusion of carbon and oxygen starts in the center then rapidly consumes the entire star, which then blows the star completely apart. In the nuclear hellfire of the blast, massive amounts of elements ranging from neon to nickel are generated then hurled into space where they subsequently become incorporated into new stars, planets and presumably, life elsewhere in the Universe. These immensely powerful blasts can be seen for billions of light years, and because they are all more or less equally powerful are useful yardsticks to measure vast distances across the Universe.
Once I located NGC-4424 with the 10-inch, I used higher and higher powered eyepieces until the 4.7mm Explore Scientific 82 degree eyepiece revealed it's presence at 280X. It appeared as a pip of light very close to NGC-4424's inner core the flitted in an out visibility due to the average seeing that night. This supernova had an apparent magnitude of 12 or so, whereas the galaxy itself is small, fairly bright and elongated with an intense inner core. I would rate this galaxy as fairly bright and easy for an 8 or 10-inch telescope, and under good skies in range of smaller telescopes too with an apparent magnitude of 11.5 or so. Once I found and observed NGC-4424 and it's ongoing supernova, I turned my attention next to the galaxies of Coma Berenice's, whose name actually comes from a queen by the same name who lived in what is now Tripoli Libya. She was the wife of Ptolemy III and famous for her beauty, which included long blond hair. When he was off fighting a war, legend has it she sacrificed her hair to the goddess Aphrodite to ensure he would return alive and well. When he did come back, he was very surprised to see his wife sporting the short look, but an astronomer showed the royal couple Coma Berenice's and told them Aphrodite placed her hair in the sky.
Coma Berenice's is dominated by a large open cluster that does resemble a woman's disheveled long hair, but it also harbors huge numbers of galaxies. The first to be observed was the oval, small and bright elliptical galaxy NGC-4494. It rapidly brightens to an intense, and bright inner core at 227X. It's actually a good galaxy for a much smaller telescope than my 15-inch, I've seen it a number of times with my 6-inch.
Nearby is probably the most famous galaxy in Coma Berenice's, NGC-4565. Also known as "Bernice's Hair Clip" this galaxy is quite possibly the best edge-on galaxy in the northern skies for smaller telescopes. In photos it's over 20 arc-minute long, but the rather poor skies limited that to perhaps half that night. Nevertheless, the bright inner core, the dust lane that runs along most of the length of the disk and the thin, fried egg like cross section were at least hinted at if not glaring evident at 227X through the 15-inch. Despite the poor skies, it was still impressive even through the 24mm 82 degree Explore Scientific eyepiece at 83X.
Not far from NGC-4469 and NGC-4565 is the Coma Cluster, a galaxy cluster about 350 million light years away. It's brightest galaxies are NGC-4889 and NGC-4874, surrounded by dozens and dozens of dimmer NGC, UGC and PGC galaxies. At 227 and 298X, indeed there were other galaxies visible though some were very hard to spot in the less than ideal skies. A check of my star chart program shows they are NGC-4898, NGC-4886, NGC-4876, NGC-4869, and NGC-4872, all of which range in magnitude from 13.5 to 15.0, little NGC-4898 being the dimmest and smallest of the lot, although I am not quite sure why I spotted it and others nearby of the same magnitude went undetected. Undoubtedly, from a truly dark site, there would be 20 or 30 dimmer galaxies visible where NGC-4889 and 4874 are located through the 15-inch.
Heading back into Virgo, I visited the pair of galaxies NGC-5363 and 5364. This consists of a tenth magnitude elliptical galaxy and a much fainter 10th magnitude spiral galaxy which is more elongated and spread across a much larger area of sky. In the poor sky conditions I was able only to see the inner region of this nearly face-on spiral. Both made a nice pair at 142X.
Nearby, I stopped by another pair of Virgo galaxies, NGC-5426 and NGC-5426 was bare visible with a weak central brightening, and it was clearly not round like NGC-5427. This pair is worthy of a return visit from a truly dark site where the 15-inch will show both far better than it ever could from the club's light polluted observing site.

Other objects I observed that night included the planets Mercury, Mars and Saturn. All suffered the effects of the rather poor seeing, so I concentrated on galaxies and nebulae. Other objects I visited included the Ursa Minor galaxy NGC-6217, which is an oval glow marked by patches of greater brightness than the surrounding disk, no doubt star forming regions in this galaxy. The nebulae M-57, M-8, M-20 and M-17 were also visited. The dark lanes in M-20 were stunningly apparent, and the dark lanes and bright steaks in M-8 made it look almost three dimensional through the 15-inch. M-17 looked like the chaotic cloud of hot gas it is, with a vast outer halo visible. The Veil Nebula also showed it's striations too, and the structure of the Ring and Dumbbell nebulae were also clearly apparent. M-27 also showed it's central star, whereas the rather poor seeing hid M-57's central star from view. Finally, I looked at Omega Centauri, but the thick haze near the horizon made its stars merge into a fuzzy blob. It was a most rewarding night despite the hazy skies and the passing clouds.

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