dust, creating a starburst around the galaxy's center portion that went unscathed as it expanded outwards. This explains the bluish ring around the center, brighter portion. It can be noted that the galaxy is beginning to retake the form of a normal spiral galaxy, with arms spreading out from a central core. These arms are often referred to as the cartwheel's “spokes”. Alternatively, a model based on the gravitational Jeans instability of both axisymmetric (radial) and nonaxisymmetric (spiral) small-amplitude gravity perturbations allows an association between growing clumps of matter and the gravitationally unstable axisymmetric and nonaxisymmetric waves which take on the appearance of a ring and spokes. Based on observational data, however, this theory of ring galaxy evolution does not appear to apply to this specific galaxy. While most images of the Cartwheel display three galaxies close together, a fourth physically associated companion (also known as G3) is known to be associated with the group through an HI tail that connects G3 to the cartwheel. Due to the presence of the HI tail, it is widely believed that G3 is the “bullet” galaxy that plunged through the disk of the cartwheel, creating its current shape, not G1 or G2. This hypothesis makes sense given the size and predicted age of the current structure (~300 million years old as mentioned before). Considering how close G1 and G2 are to the Cartwheel still, it is much more widely believed that the roughly 88 kpc (~287,000 light years) distant G3 is the intruding galaxy. Neutral hydrogen tail mapping is extremely useful in determining “culprit” galaxies in similar cases where the answer is relatively unclear. Hydrogen gas, being the lightest and most abundant gas in galaxies, is easily torn away from parent galaxies through gravitational forces. Evidence of this can be seen in the Jellyfish Galaxy and the Comet Galaxy, which are undergoing a type of gravitational effect called ram pressure stripping, and other galaxies with tidal tails and star forming stellar streams associated with collisions and mergers. Ram pressure stripping will almost always cause trailing-dominant tails of HI gas as a galaxy infalls into a galaxy cluster, while mergers and collisions like the cartwheel often create leading-dominant tails as the culprit galaxy’s gravity attracts and pulls on the victim galaxy’s gas in the direction of the culprit's motion. The existing structure of the cartwheel is expected to disintegrate over the next few hundred