The Bullet Cluster

The Bullet Cluster is a pair of colliding galaxy clusters, observed in space, that provides strong evidence for dark matter. During the collision, hot gas from the clusters interacts and slows down, emitting X-rays. However, most of the mass, inferred from gravitational effects, remains slightly ahead, indicating the presence of unseen matter—dark matter—that doesn't interact strongly with regular matter. This separation between normal matter and total mass helps scientists confirm that dark matter exists, making the Bullet Cluster a crucial piece of evidence in understanding the universe's unseen components.