Astronomy Picture of the Day
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2002 November 11 
Posted on 11/11/2002 12:44:41 AM PST by petuniasevan
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2002 November 11
Explanation: What causes the surrounding shells in peculiar galaxy Cen A? Last month a fascinating image of peculiar galaxy Centaurus A was released, processed to highlight a faint blue arc indicating an ongoing collision with a smaller galaxy. Another interesting feature of Cen A, however, is the surrounding system of shells, better visible here in this recently released wider pan from the four meter Blanco telescope at Cerro Tololo Inter-American Observatory. Faint shells around galaxies are not unusual and considered by themselves as evidence of a previous galaxy merger, analogous to water ripples on a pond. An unexpected attribute of these shells is the abundance of gas, which should become separated from existing stars during the collision.
It's worth repeating the montage of images I put up on 10-17-02.
10-17-02 Young blue star stream in Centaurus A.
It's a close-up of today's image.
8-12-02 composite image radio, optical light, x-rays
4-21-02 mosaic of Hubble images in red, green, blue light
2-02-02 composite optical, infrared, and radio lobe outlines traced
8-16-01 Chandra false-color x-ray image - see the jet?
10-28-99 composite optical and x-ray image (Chandra)
3-30-97 optical image Cerro Tololo Observatory
Some of these images were repeated over the years; the Hubble mosaic from 4-21 had been featured 3 times previously!
Notice that the narrow part of the electromagnetic spectrum we call "light" is only a part of the story!
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