Thin Disk

The defining morphological component of disk galaxies in general and spiral galaxies in particular. The thin disk contains stars, starSelf-luminous object held together by its own self-gravity. Often refers to those objects which generate energy from nuclear reactions occurring at their cores, but may also be applied to stellar remnants such as neutron stars. clusters, gas and dust confined to the galaxy’s plane of rotation. There is much more information on the disk of the Milky Way than for spiral galaxies, but the disk of the Milky Way is considered typical.

Thin disks contain the majority of the baryonic material in spiral galaxies (on the order of 80% of the baryonic material in the Milky Way is in the thin disk). The thin disk of the Milky Way has a scale height of ~400 light years and scale length of ~10,000 light years and rotates about the galactic center at ~220 km/sec. Its outer regions appear to be warped, a phenomenon observed in ~50% of spiral galaxies. Although the origin of warps is uncertain, it is thought that they are probably the result of galaxyConcentration of 10⁶ to 10¹² stars, dust and gas, that are gravitationally bound. Our galaxy contains ~2 × 10¹¹ stars. There are four main types of galaxies: • Elliptical
• Lenticular
• Spiral
• Irregular
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The thin disks of spiral galaxies contain a lot of gas and dust, and an active site for ongoing star formation, especially in the spiral arms. For this reason, stars in the thin disk tend to be relatively young (average age ~6 Ga), although individual ages range from 0–10 Ga. This is evidence for secular evolution in thin disks. Thin disk stars also tend to be metal-rich compared to thick diskFeatures believed to exist in some, but not all disk galaxies; it clear whether the thick disk of the Milky Way Galaxy is typical of thick disks in other spiral galaxies. The thick disk contains about 10% of the stellar mass of the Milky Way and has a scale height and halo stars, and typically have similar metallicities to the SunOur parent star. The structure of Sun's interior is the result of the hydrostatic equilibrium between gravity and the pressure of the gas. The interior consists of three shells: the core, radiative region, and convective region. Image source: http://eclipse99.nasa.gov/pages/SunActiv.html. The core is the hot, dense central region in which the (a thin disk star).