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4 years ago in Cosmology , Particle Physics By Rassika Jain
What is the concept of dark matter in astronomy and cosmology?
I'm familiar with galaxy rotation curves as the classic evidence, but I know MOND was designed to fit those. In recent years, what observation or dataset has been most decisive in the community's consensus that dark matter is a particle? I'm thinking of instances where gravity and visible matter are clearly separated, like in colliding galaxy clusters.
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By Seema Answered 4 years ago
For many, the most persuasive single observation is the Bullet Cluster. Here, two galaxy clusters collided. The hot, X-ray emitting gas (the bulk of the normal matter) was slowed by friction and sits in the center. However, the total mass map, reconstructed via gravitational lensing, shows the peaks of mass are with the galaxies, which passed through each other. This demonstrates that most of the mass is collisionless and separate from the baryonic gasa direct visualization of "dark matter." Modified gravity theories, which tie force to visible mass, struggle immensely to explain this spatial separation without invoking some unseen, particle-like component.
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