Question

Provide a description of our home galaxy, the Milky Way. Include in your description the location and stellar populations (new stars/ old stars) of the central bulge, disk, and halo. Also provide details such as the Hubble classification, disk structure, location of star forming regions, and the best estimate of the number of spiral arms.

Answer 1

Milky way is the galaxy in which our solar system falls. From earth it appears as a band in night sky. It has a disk like structure with a diameter of around 200,000 light years. It contains around 100-400 billion stars and many planets also. It is located at a distance of 27,000 light years from the center. In the inner parts of milky way (around 10,000 light years radius) lies most of the old stars in an approximately spheroidal shape called bulge. Stars in milky way are distributed in four arms. A spherical population of stars surrounds the milky way. This spherical region is called Halo.

Hubble classification : Under Hubble classification Milky way closely resembles type Sbc which means that spiral arms in galaxy ware loosely wound. .

Disk structure : Disk of milky ways contains along with stars, gas and dust which is called the interstellar medium. There is no sharp edge of milky way disk, beyond which there are no stars. Concentration of stars in disk decreases with distance from center.

Star formation : It occurs in the central part of the milky way. Roughly in the region with a radius of 640 light years star formation happens.

Number of spiral arms : There are four spiral arms in milky way