A Stellar Census - Astronomy 121

Flashcards covering key concepts from the Astronomy 121 lecture on stellar characteristics, measurements, and relationships.

What is a light-year?

The distance that light travels in one year, approximately 9.5 trillion kilometers.

Why are only a few of the brightest stars close to the Sun?

Most bright stars are high-luminosity but are not necessarily close; there are many more low-luminosity stars.

What is the mass-luminosity relation?

A relationship stating that luminosity (L) is proportional to mass (M) raised to the power of approximately 3.9.

How does the mass of a star influence its lifetime?

A star's lifetime is inversely proportional to the mass cubed (lifetime ∝ 1/M^3).

What types of binaries can be used to study star masses?

Visual binaries (both stars visible) and spectroscopic binaries (one star appears single but is actually double).

What technique allows astronomers to measure the diameter of eclipsing binaries?

By examining the light curve during eclipses to determine how long one star blocks the other.

Define what an H-R diagram illustrates.

A graph that plots the absolute magnitude (luminosity) of stars against their temperature or spectral type.

What characterizes white dwarf stars?

White dwarfs are small, hot stars with low luminosity, thought to be the end stage of most star life cycles.

Who discovered that the brightest visible star, Sirius, is a binary system?

Sirius is known to be a binary system where Sirius B is a white dwarf.

What percentage of stars are main sequence stars?

Approximately 90% of all stars observed lie along the main sequence on the H-R diagram.