Galaxy season continues. May was a mixed bag for imaging for the Hubble Challenge. Some targets proved quite challenging, and it was difficult to get any decent amount of exposure time to produce something that wasn’t a bleary smudge. The best of the rest are featured here. More information on the challenge can be found on the Pennsylvania Night Sky page.
Our first subject is the Whirlpool Galaxy, also known as Messier 51a (M51a) or NGC 5194, an interacting grand-design spiral galaxy. It lies in the constellation Canes Venatici, and was the first galaxy to be classified as a spiral galaxy. It is 31 million lightyears (9.5 megaparsecs/Mpc) away and 23.58 kiloparsecs (76,900 ly) in diameter.
The galaxy and its companion, the dwarf galaxy NGC 5195, are interacting with each other. They are easily observed, and the two galaxies may even be seen with binoculars under the right conditions. The Whirlpool Galaxy has been extensively observed by professional astronomers, who study it and its pair with dwarf galaxy NGC 5195 to understand galaxy structure (particularly structure associated with the spiral arms) and galaxy interactions. Its pair with NGC 5195 is among the most famous and relatively close interacting systems, and thus is a favorite subject of galaxy interaction models.
I had a lot more integration time for this shot (about 4 hours). Although it won’t be winning any awards, I am pretty please with this image at this stage of my learning process. Compare the distinct spiral arms of M51 with the other galaxies featured below.
Caldwell 21, also known as NGC 4449, is an irregular Magellanic type galaxy in the constellation Canes Venatici, being located about 13 million light-years away. It was discovered by German-British astronomer William Herschel on 27 April 1788. It is part of the M94 Group or Canes Venatici I Group that is relatively close to the Local Group hosting our Milky Way galaxy. This galaxy is similar in nature to the Milky Way’s satellite galaxy, the Large Magellanic Cloud, though is not as bright nor as large. C21 has a general bar shape, also characteristic of the LMC, with scattered young blue star clusters. The bar shape can be seen in the image.
Caldwell 52 (NGC 4697) is an elliptical galaxy some 40 to 50 million light-years away in the constellation Virgo. It is a member of the NGC 4697 Group, a group of galaxies also containing NGC 4731 and several generally much smaller galaxies. This group is about 55 million light-years away; it is one of the many Virgo II Groups, which form a southern extension of the Virgo Supercluster of galaxies. The distance to NGC 4697 is not known with high precision: measurements vary from 28 to 76 million light-years. According to the NASA Extra-galactic Database, the average is about 38 million light-years; according to SIMBAD, about 50 million light-years.
Messier 87 (also known as NGC 4486) is a supergiant elliptical galaxy in the constellation Virgo that contains several trillion stars. One of the largest and most massive galaxies in the local universe it has a large population of globular clusters, about 15,000 compared with the 150–200 orbiting the Milky Way, and a jet of energetic plasma that originates at the core and extends at least 1,500 parsecs (4,900 light-years). It is one of the brightest radio sources in the sky and a popular target for both amateur and professional astronomers.
The French astronomer Charles Messier discovered M87 in 1781, and cataloged it as a nebula. M87 is about 16.4 million parsecs (53 million light-years) from Earth and is the second-brightest galaxy within the northern Virgo Cluster, having many satellite galaxies. Unlike a disk-shaped spiral galaxy, M87 has no distinctive dust lanes. Instead, it has an almost featureless, ellipsoidal shape (evident below) typical of most giant elliptical galaxies, diminishing in luminosity with distance from the center.
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