Cartwheel galaxy

The Cartwheel galaxy (also known as ESO 350-40) is a lenticular galaxy about 500 million light-years away in the constellation Sculptor.Moore, Patrick 2000. The data book of Astronomy. CRC Press, 318. 

It is about 150,000 light years across, slightly larger than the Milky Way. It has a mass of about  solar masses, and rotates at .

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

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

 Evolution 
The galaxy was a normal spiral galaxy before it had a collision with a smaller galaxy about 200 million years ago.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. 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. 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.

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

References

Other websites
Galaxy evolution simulation: the Cartwheel Galaxy 

Category:Lenticular galaxies
Category:Starburst galaxies
Category:Ring galaxies

de:Ringgalaxie#Wagenradgalaxie