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 considered his discovery to be "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 [change]

The galaxy was once a normal spiral galaxy before it had a head-on collision with a smaller companion about 200 million years ago.[3][7][8] When the nearby galaxy passed through the Cartwheel Galaxy, the force of the collision caused a powerful shock wave through the galaxy. Moving at high speed, the shock wave swept up gas and dust, creating a starburst around the galaxy's centre (which was undisturbed). This explains the bluish ring around the center, brighter portion.[9] It can be seen that the galaxy is beginning to retake the form of a normal spiral galaxy, with arms spreading out from a central core.[8]

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

References [change]

  1. ↑ Moore, Patrick 2000. The data book of Astronomy. CRC Press, 318. ISBN 0-7503-0620-3
  2. ↑ "Amazing Space - fast facts: Cartwheel Galaxy". Amazing Space. 2008. http://amazing-space.stsci.edu/resources/fastfacts/cartwheel_galaxy.php.p=Astronomy+basics@,eds,astronomy-basics.php&a=,eds. Retrieved 2009-07-03.
  3. ↑ 3.0 3.1 Amram P. et al (1998). "The Hα kinematic of the Cartwheel galaxy". Astron Astrophys. 330: 881–93.
  4. ↑ 4.0 4.1 Zwicky F (1941). Theodore van Karman Anniversary volume: contribution to applied mechanics and related subjects. Pasadena, California: California Institute of Technology. p. 137.
  5. ↑ 5.0 5.1 Griv E (2005). "Origin of the Cartwheel Galaxy: disk instability?". Astrophys Space Sci. 299 (4): 371–85. doi:10.1007/s10509-005-3423-5.
  6. ↑ Mayya YD et al. (2005). "The discovery of spiral arms in the starburst galaxy M82". Ap J. 628 (1): L33. 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 Galaxy". College of Southern Nevada. http://sites.csn.edu/planetarium/galaxy.html. Retrieved 2009-07-03.
  9. ↑ Platt, Jane (2006). "Cartwheel galaxy makes waves in new NASA image". NASA. http://www.nasa.gov/mission_pages/galex/galex-20060111.html. Retrieved 2009-05-15.

Other websites [change]

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