Tully-Fisher relation

Definition

The Tully-Fisher relation is an empirical relationship between the luminosity of a spiral galaxy and its rotational velocity. It serves as a key tool in measuring the distances to spiral galaxies.

5 Must Know Facts For Your Next Test

1. The Tully-Fisher relation only applies to spiral galaxies.
2. The rotational velocity of a galaxy can be measured using Doppler shifts of spectral lines.
3. Brighter spiral galaxies tend to have higher rotational velocities.
4. It is often used in conjunction with redshift measurements to estimate distances in the universe.
5. The Tully-Fisher relation helps astronomers determine the Hubble constant and understand the expansion rate of the universe.

Related terms

Redshift:

The increase in wavelength (and corresponding decrease in frequency) of light from objects moving away from an observer, commonly used to measure distances to far-away galaxies.

Hubble Law: The observation that more distant galaxies are receding faster, leading to the conclusion that the universe is expanding.

Doppler Effect:

A change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source, crucial for measuring galactic velocities.