AST201H1 Chapter Notes - Chapter 23: Elliptical Galaxy, Gravitational Lens, Spiral Galaxy

• School: UTSG
• Department: Astronomy & Astrophysics
• Course: AST201H1
• Professor: Michael Reid

Document Summary

Chapter 23: dark matter, dark energy, and the fate of the universe (23. 1 . Dark matter: matter that we infer to exist from its gravitational effects but from which we have not detected any light (hence dark") it appears to dominate the total mass of the universe. Studies of the mw"s rotation suggest that most of our galaxy"s mass is distributed throughout its halo while most of its light comes from stars/gas clouds in the thin galactic disk. Dark energy: name given to energy that could be causing the expansion of the universe to accelerate. Dark matter/energy were each proposed to exist because they seemed the simplest ways to explain observed motions in the universe. Mw by performing the above calculation for stars at every different distance from the galactic center. Radio waves penetrate dust, and clouds of atomic hydrogen gas emit a spectral line at the radio wavelength of 21cm.