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The Virgo Supercluster

Virgo Supercluster The Milky Way is a member of the Local Group of galaxies, which in turn is a part of the Virgo supercluster (see Figure 03-06a). It is centered on the Virgo cluster and extends some 150 million light years across. The Virgo cluster itself contains thousands of galaxies including M87, which is known to surround a gigantic black hole. Virgo's gravity affects the movement of its neighbors, including the Local Group. The supercluster is the last outpost before a space traveler would enter a nearly galaxy-free region called a cosmic void. Actually, even the supercluster has a mass equaling some thousand trillion suns, virtually all its volume is empty in such a vast space. The Local Group of galaxies extends some 4 million light years across. Most galaxies in the group are considered dwarfs, but the two largest - the Milky Way and the Andromeda galaxy - are giant spirals moving toward each other at a speed of about 100 km/sec. All the galaxies of the Local Group are traveling together through space - indicating a common origin.

Figure 03-06a Virgo Supercluster
[view large image]

Figure 03-06b is the NASA/ESA vision of the galactic encounter between the Andromeda galaxy and the Milky Way ending with the formation of a giant elliptical galaxy some 7 billion years in the future. As the Sun evolves toward its dying phase, The Earth would become inhabitable about 1.2 billion years from now, and it will melt under the expanding Sun in another 6.5 billion years.

Galactic Encounter

Figure 03-06b Galactic Encounter [view large image]

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