Astronomy 1021 Lecture Notes - Lecture 15: Density Wave Theory, Ultraviolet, Sagittarius A*
3 Apr 2016
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Document Summary
Our galaxy consists of a lat disk with spiral arms, a central bulge, and a roughly spherical halo surrounding everything. Clouds of interstellar gas and dust known as interstellar medium ill the galacic disk, obscuring most of the galaxy when we observe with visible light. The milky way is a large galaxy and several smaller galaxies orbit it. Each individual star follows its own orbital path around the centre of the galaxy. The nature of its orbital path depends primarily on whether the star resides in the disk, the halo, or the bulge. Disk stars orbit the galaxy"s centre in orderly circles that all go in the same direcion, bobbing slightly up and down as they orbit. Halo stars swoop high above and below the disks on randomly orientated orbits. Some bulge stars orbit like halo stars while others orbit like disk stars.
