The Cartwheel Galaxy And Its Companion Galaxies. Key Ring

The Cartwheel Galaxy and its companion galaxies. This galaxy formed as the result of a high-speed collision that occurred about 400 million years ago. The Cartwheel is composed of two rings, a bright inner ring and a colourful outer ring. Both rings expand outward from the centre of the collision like shockwaves. Despite the impact, much of the character of the large, spiral galaxy that existed before the collision remains, including its rotating arms. This leads to the spokes that inspired the name of the Cartwheel Galaxy, which are the bright red streaks seen between the inner and outer rings. These brilliant red hues, located not only throughout the Cartwheel, but also the companion spiral galaxy at the top left, are caused by glowing, hydrocarbon-rich dust. Amidst the red swirls of dust, there are many individual blue dots, which represent individual stars or pockets of star formation.