Galaxies

• Galaxies are made of stars, gas, dust, and other celestial bodies.
• Galaxies form the universe's building blocks.
• The 3 types of galaxies are spiral, elliptical, and irregular.
• Elliptical galaxies are circular to elongated, with little gas and dust, containing older stars.
• Spiral galaxies have flat disks with central bulges, actively forming stars.
• Spiral galaxies are divided into normal and barred. Barred spiral galaxies have elongated central bulges and the normal ones have arms originating from the center. Normal ones are more spherical.
• Both the Milky Way and Andromeda galaxies are barred spirals.
• Irregular galaxies lack a defined shape.
• 2/3 of spiral galaxies are barred.
• Galaxies formed due to the change of densities after the Big Bang. Clouds of dusts collapse due to gravity, forming stars in it, making a galaxy.
• Many galaxies are formed through collisions of matter with other existing galaxies.
• The cosmic evolution states that galaxies form and evolve through interactions with stars groups and other galaxies.
• Edwin Hubble supports the expanding universe theory, which states that galaxies formed after the Big Bang.
• Galaxies can interact and collide, leading to star formation, supernovas, and black holes.
• Collisions can distort galaxies’ shapes and may lead to ellipticals.
• Milky Way and Andromeda are on a collision course, which is a part of galactic evolution.
• Milky Way is set to collide with Andromeda which is currently 2.5 million light years away. The Triangulum galaxy might also join this collision.
• Galaxies can pass through each other without stars colliding due to immense interstellar distances.
• Vera Rubin’s studies in the 1970s led to the discovery of dark matter, which constitutes about 84% of the universe’s material.
• Vera Rubin discovered dark matter due to the Bullet Cluster’s collision that provided insights into dark matter’s gravitational effects, separating it from normal matter.
• Galaxies can be starbursting, have black holes at their

  centers, and are part of larger structures like clusters and superclusters.
• Galaxies can be starbursting, have black holes at their centers, and are part of larger structures like clusters and superclusters.