Mass-to-light ratio

Definition

Mass-to-light ratio is a measurement used in astronomy to compare the total mass of an object, such as a galaxy, to its luminosity. It provides insights into the presence of dark matter and helps astronomers understand the composition and evolution of galaxies.

5 Must Know Facts For Your Next Test

1. A high mass-to-light ratio suggests the presence of dark matter in a galaxy.
2. The mass-to-light ratio is typically measured in solar units (M☉/L☉).
3. Spiral galaxies generally have lower mass-to-light ratios compared to elliptical galaxies.
4. Mass-to-light ratios can vary significantly within different regions of the same galaxy.
5. This ratio is crucial for determining whether visible matter alone can account for the gravitational effects observed in galaxies.

Review Questions

• What does a high mass-to-light ratio indicate about a galaxy?
• In what units is the mass-to-light ratio usually measured?
• How do spiral and elliptical galaxies differ in terms of their typical mass-to-light ratios?

Related terms

Dark Matter: A form of matter that does not emit light or energy, detectable only through its gravitational effects.

Luminosity: The total amount of light emitted by an object, often measured in watts or solar luminosities.

Gravitational Lensing: The bending of light from a distant source due to the gravitational field of an intervening massive object.