million years as the remaining gas, dust and stars that haven’t escaped the galaxy begin to infall back towards the center. It is likely that the galaxy will regain a spiral shape after the infall process completes and spiral density waves have a chance to reform. This is only possible if companions G1, G2 and G3 remain distant and do not undergo an additional collision with the cartwheel. X-ray sources The unusual shape of the Cartwheel Galaxy may be due to a collision with a smaller galaxy such as one of those in the lower left of the image. The most recent star burst (star formation due to compression waves) has lit up the Cartwheel rim, which has a diameter larger than that of the Milky Way. Star formation via starburst galaxies, such as the Cartwheel Galaxy, results in the formation of large and extremely luminous stars. When massive stars explode as supernovas, they leave behind neutron stars and black holes. Some of these neutron stars and black holes have nearby companion stars, and become powerful sources of X-rays as they pull matter off their companions (also known as ultra and hyperluminous X-ray sources). The brightest X-ray sources are likely black holes with companion stars, and appear as the white dots that lie along the rim of the X-ray image. The Cartwheel contains an exceptionally large number of these black hole binary X-ray sources, because many massive stars formed in the ring. References External links Galaxy Evolution Simulation:The Cartwheel Galaxy Cartwheel Galaxy at Constellation Guide Webb Captures Stellar Gymnastics in The Cartwheel Galaxy nasa.gov Lenticular galaxies Peculiar galaxies Ring galaxies Sculptor (constellation) 02248 Astronomical objects discovered in 1941