Cartwheel galaxy

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A spectacular head-on collision between two galaxies is seen in this NASA Hubble Space Telescope true-color image of the Cartwheel Galaxy.
The Cartwheel galaxy in different spectra (X-ray, ultraviolet, visible light, and infrared). The image combines data from four different space-based observatories: the Chandra X-ray Observatory (purple), the Galaxy Evolution Explorer (ultraviolet/blue), the Hubble Space Telescope (visible/green), and the Spitzer Space Telescope (infrared/red).

The Cartwheel galaxy (also known as ESO 350-40) is a lenticular galaxy about 500 million light-years away in the constellation Sculptor.[1]

It is about 150,000 light years across, slightly larger than the Milky Way.[2] It has a mass of about 2.9–4.8 × 109 solar masses, and rotates at 217 km/s.[3]

It was discovered by Fritz Zwicky in 1941.[4] Zwicky said his discovery was "one of the most complicated structures awaiting its explanation on the basis of stellar dynamics".[4][5]

The Cartwheel galaxy shows radio and optical spokes, but they are not the same spokes.[6]

Evolution

The galaxy was a normal spiral galaxy before it had a collision with a smaller galaxy about 200 million years ago.[3][7][8] When the nearby galaxy passed through the Cartwheel Galaxy, the power of the collision sent a strong shock wave through the galaxy. Moving at high speed, the shock wave moved gas and dust. This made a starburst around the galaxy's center. This explains the blue colored ring around the center, bright section.[9] It can be seen that the galaxy is beginning to take the shape of a normal spiral galaxy again, as spiral arms (The spokes) are spreading out from a central core.[8]

There are other possible explanations of the ring-like appearance.[5]

References

  1. ↑ Moore, Patrick 2000. The data book of Astronomy. CRC Press, 318. ISBN 0-7503-0620-3
  2. ↑ Amazing Space - fast facts: Cartwheel Galaxy (2008)Amazing Space. Retrieved 2009-07-03.[dead link]
  3. ↑ 3.0 3.1 Amram P.. The Hα kinematic of the Cartwheel galaxy. Astron Astrophys. 330 (1998). p. 881–93.
  4. ↑ 4.0 4.1 Zwicky F. Theodore van Karman Anniversary volume: contribution to applied mechanics and related subjects (1941). Pasadena, California: California Institute of Technology. p. 137.
  5. ↑ 5.0 5.1 Griv E. Origin of the Cartwheel Galaxy: disk instability?. Astrophys Space Sci. 299 (4) (2005). p. 371–85. doi:10.1007/s10509-005-3423-5.
  6. ↑ Mayya YD. The discovery of spiral arms in the starburst galaxy M82. Ap J. 628 (1) (2005). p. L33–L36. doi:10.1086/432644.
  7. ↑ That is, 200 million years before the image. We see the galaxy as it was 500 million years ago, and the collision took place 700 million years ago.
  8. ↑ 8.0 8.1 Cartwheel GalaxyCollege of Southern Nevada. Retrieved 2009-07-03.
  9. ↑ Platt, Jane. Cartwheel galaxy makes waves in new NASA image (2006)NASA. Retrieved 2009-05-15.

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