This image captures a portion of the vast Virgo Galaxy Cluster. See the images of galaxies M84, M86, M87 and M105 for additional images of this cluster. All of the prominent galaxies in these images are members of this vast system of galaxies, and all are about 60 million light years away.
This image depicts over 20 galaxies. The brightest galaxy is the giant elliptical galaxy M60 (left edge of the image), and its close companion is the spiral galaxy NGC 4647. The bright galaxy in the bottom right is M59.
Whenever you see a pair of galaxies like M60 and NGC 4647 it is important to understand that they may be a true "physical pair" (meaning that they are close together, at about the same distance from Earth, and are gravitationally connected), or they may be a "line of sight" double (two galaxies that appear close together but in fact contain a foreground galaxy and a far more remote background galaxy). Astronomers can easily tell the difference by measuring the spectral redshifts of both galaxies in a pair since redshifts are associated with recessional velocity. Spectral lines are the black lines that appear in spectra of stars, and they correspond to the elements and molecules in a star. These spectral lines are shifted to the red end of the visible spectrum when an object is moving away from us, since the wavelengths of light are being stretched from our perspective. This is due to the "Doppler effect." While this effect is most commonly associated with sound waves, it also applies to electromagnetic radiation (light). Distance can be correlated to the intensity of redshifted spectral lines in a star or galaxy. The greater the redshift, the faster the recessional velocity of the object.
Astronomers have determined that M60 and NGC 4647 are a physical double. Upon close examination you can detect subtle distortions in the spiral arms of NGC 4647 caused by the gravitational force exerted by M60. In January of 2004, a Type IA supernova (supernova 2004W) appeared in M60 (just to the left of the two stars at the bottom of its halo). Astronomers believe that the supernova occurred several months earlier, but had gone undetected. One of the exciting aspects of imaging galaxies is the ever present possibility of detecting a supernova explosion.
Supernovae are cataclysmic explosions of massive stars at the end of their burning cycle. A Type IA supernova occurs in binary star systems containing a white dwarf star. If the white dwarf is able to absorb sufficient mass from its companion, its mass will be sufficient to trigger runaway fusion of carbon and oxygen in the core because of the enormous temperatures achieved by the gravitational contraction of the star produced by the accumulation of additional mass. This condition causes an explosion of almost unimaginable force. The white dwarf star (with a radius approximately the size of Earth) suddenly attains a luminosity equal to 10 billion or more stars! But, this prodigious energy output cannot last long, and the supernova quickly fades over several weeks and months. As you look at the images of galaxies on this website, you may be able to find a supernova. After all, the 2004 supernova was not observed for several months after it occurred.
M60 and the Virgo Galaxy Cluster
Date Taken:May 4, 2005
Location Taken: Conditions of Location:FWHM 2.5
Equipment Used:Takahashi TOA-130 5" apochromat refractor telescope, SBIG ST-10XME CCD camera, Optec TCF-S focuser, Astrodon RGB filters.
Processing Used:6x10 minutes H-alpha, and 6x90 sec RGB, guided, processed in Maxim DL and Photoshop
Distance from Location:60 million light years
Constellation:Virgo (the "virgin")
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