Cartwheel galaxy

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]


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. Spiral arms are spreading out from a central core.[8]

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


  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. 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. Bibcode:1998A&A...330..881A.
  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. Bibcode:2005Ap&SS.299..371G. 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. arXiv:astro-ph/0506275. Bibcode:2005ApJ...628L..33M. 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. Retrieved 2009-07-03.
  9. Platt, Jane (2006). "Cartwheel galaxy makes waves in new NASA image". NASA. Retrieved 2009-05-15.

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