Chapter 26

These flashcards cover key terms and concepts discussed in the lecture on galaxies, including types of galaxies, significant astronomical discoveries, and fundamental laws of astrophysics.

Spiral Galaxy

A type of galaxy characterized by a flattened, rotating structure with pinwheel-like arms of interstellar material and young stars, such as the Milky Way.

Andromeda Galaxy (M31)

The nearest spiral galaxy to the Milky Way, located about 2.5 million light-years away.

Hubble Space Telescope

A space telescope that has provided significant insights into the existence and properties of galaxies.

Cepheid Variable Stars

A type of star used as a standard candle for measuring astronomical distances based on its brightness and periodic variations.

Hubble's Law

A law stating that the radial velocities of remote galaxies are proportional to their distances from us.

Elliptical Galaxy

A type of galaxy that is elliptical in shape and contains predominantly old stars with little interstellar matter.

Irregular Galaxy

A galaxy without a distinct regular shape, which often undergoes intense star formation.

Redshift

The displacement of spectral lines toward longer wavelengths, indicating that an object is moving away.

Hubble Constant

The proportionality constant in Hubble's law, representing the rate of expansion of the universe, expressed in kilometers per second per million light-years.

Mass-to-Light Ratio

A measure that compares the mass of a galaxy to its luminosity; it indicates the types of stars within the galaxy and the presence of dark matter.

Type Ia Supernova

A supernova occurring in a binary system, which serves as a standard bulb for measuring cosmic distances due to its consistent peak brightness.