Spiral Arms and Stars: The Milky Way is a barred spiral galaxy, characterized by its distinct spiral arms that contain billions of stars. Our Solar System is located within one of these spiral arms, known as the Orion Arm or Local Spur.
Galactic Size and Scale: The Milky Way is estimated to be about 100,000 light-years in diameter and contains over 200 billion stars. It’s just one of the estimated 2 trillion galaxies in the observable universe.
Galactic Speed: Despite its massive size, the Milky Way is not stationary. Our solar system orbits the center of the galaxy at a speed of about 514,000 miles per hour (828,000 kilometers per hour), completing a full rotation every 225-250 million years.
Black Hole at the Core: At the center of the Milky Way lies a supermassive black hole called Sagittarius A* (pronounced “Sagittarius A-star”). It has a mass roughly equivalent to 4.3 million suns and influences the motion of nearby stars.
Galactic Halo and Dark Matter: Surrounding the visible disk of the Milky Way is a halo of dark matter, a mysterious substance that exerts gravitational influence but doesn’t emit light. Dark matter is believed to account for a significant portion of the galaxy’s mass.
Galactic Cannibalism: The Milky Way has a history of interacting with and absorbing smaller satellite galaxies. The remnants of these galactic mergers can still be observed today in structures like the Magellanic Clouds, which are satellite galaxies orbiting the Milky Way.
Star Formation Regions: Within the spiral arms, regions known as stellar nurseries give birth to new stars. These nurseries are rich in gas and dust, which condense under gravity to form stars and planetary systems.
Galactic Recycling: Elements like carbon, oxygen, and iron are created in the cores of massive stars through nuclear fusion. When these stars eventually explode as supernovae, they release these elements into space, enriching the interstellar medium and providing the building blocks for new stars and planets.
Hubble’s Constant: The Milky Way is expanding along with the rest of the universe. The rate of this expansion is described by Hubble’s constant, which helps us determine the universe’s age and its past and future evolution.
Galactic Collision: The Andromeda Merger: In about 4.5 billion years, the Milky Way will experience a dramatic event: a collision with the neighboring Andromeda Galaxy. The merger will eventually lead to the formation of a new, larger galaxy dubbed “Milkomeda.”
