(a) Why is the sun considered to be located in the central disk of our galaxy? (b) What is thought to occupy the center of the disk?
(a) Milky Way photographs show a dark band running down the middle, with approximately equal numbers of stars on each side. That is the way it looks when the observer is near the central plane of the disc.
(b) A black hole has been inferred to be at the center of the Milky Way galaxy, based upon the the mass at the center as determined from velocity measurements of stars orbiting the center.
(a) The sun is considered to be located in the central disk of our galaxy because our galaxy, the Milky Way, is a flat, disk-shaped structure. When we look at the Milky Way from Earth, we see a bright band of stars stretching across the night sky, which is the edge-on view of the galactic disk. The sun resides in one of the spiral arms of this disk, about 26,000 light-years away from the center.
To understand why the sun is located in the central disk, you can follow these steps:
1. Learn about our galaxy: Gain a basic understanding of the Milky Way, its structure, and its different components.
2. Observe the night sky: Look up at the night sky to witness the band of stars that forms the Milky Way. Observe how it appears as a flat disk rather than a spheroidal shape.
3. Research galactic structure: Read about the structure of galaxies, particularly the disk-shaped structure seen in spiral galaxies like the Milky Way.
4. Explore our solar system: Understand where Earth and the sun are positioned within our solar system.
5. Locate the sun in the Milky Way: Realize that the sun is located in one of the arms of the galactic disk, which is why it is considered to be situated in the central disk of our galaxy.
(b) The center of the disk is thought to be occupied by a massive black hole called Sagittarius A* (Sgr A*). It is believed to be a supermassive black hole with a mass of around four million times that of our sun.
To learn about what occupies the center of the disk, you can follow these steps:
1. Study black holes: Understand the concept of black holes, their formation, and their characteristics.
2. Explore galactic centers: Read about the centers of galaxies and the role black holes play in them.
3. Focus on our galaxy: Research the center of the Milky Way and the specific black hole known as Sagittarius A*.
4. Learn about Sgr A*: Investigate the characteristics, observations, and scientific evidence supporting the existence of a supermassive black hole at the center of our galaxy.
5. Understand its significance: Realize that Sagittarius A* is thought to occupy the center of the disk in the Milky Way, influencing the dynamics and structure of our galaxy as a whole.