A “Stretched” Spiral Galaxy

NGC-6872 as imaged with the 8.2 meter Antu reflector, a member telescope of the VLT (Very Large Telescope) array at Cerro Paranal in the Atacama Desert, northern Chile. Other, more distant galaxies can be seen in the background along with the bright star located below and to the right of center, a foreground star in our own galaxy.

Visible to our friends south of Belize in the constellation Pavo, the Peacock, is the beautiful barred-spiral galaxy NGC (New General Catalog)-6872. Originally featured for public access at Astronomy Picture of the Day for Tuesday, 26 April, this image shows the galaxy’s true extent of 700,000 light years, or 7 times that of our Milky Way galaxy! Known as the Condor galaxy, this is one of the most elongated barred spiral galaxies known.

In this futuristic scene, occurring eons from now, our Milky Way galaxy merges with the great spiral galaxy in Andromeda

Why, you may wonder, is the galaxy so stretched out? The most likely explanation is the ongoing gravitational merger/interaction with the smaller spiral galaxy, IC4970, just above center. Spiral galaxies generally exhibit prolific star forming regions in their spiral “arms” and peripheries, regions rich in the necessary gas and dust for star formation. Driven by pressure waves along the leading edges of the spiral arms, the cold gas and dust is compressed, self-gravitates, heats up to the point where nuclear fusion reactions can occur and voila, a star is born. Single and, in many cases, multiple stars, often clusters of stars, form. Many of these stars are massive, short-lived, hot, blue stars that eventually end their life in spectacular fashion as Type-II supernovae.  They form the typical blue cast exhibited so often seen in the arms of spiral galaxies. Often times, the star formation is so intense that clusters of these high-mass stars form at the same time, producing “galactic” or “0pen” clusters that eventually disperse, intermixing with the stellar population. Enhancing the star formation process in galaxies such as NGC-6872 is the merger with other galaxies. Such an event will occur with the Great Galaxy in Andromeda and our own Milky Way in about 2.5 billion years. Characteristic of most galaxies is the warmer color of their centers, a region devoid of gas and dust, the necessary raw materials for star formation. This warmer color, decidedly more yellow than the periphery and spiral arms, is indicative of the more mature, more evolved, older stellar population contained therein.

NGC-6872 was imaged with the 8.2 meter “Antu” telescope, a member telescope of the European Southern Observatory‘s VTL (Very Large Telescope) Array, located atop Cerro Paranal in the Atacama Desert, northern Chile.

Imagination is more important than knowledge 585px-Albert_Einstein_signature_1934(invert)
An index of all articles in this blog can be found here.


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