A Relation between Distance and Radial Velocity among Extra-Galactic Nebulae
Edwin Hubble
Summary
Hubble combined distances to roughly two dozen extra-galactic nebulae (galaxies), estimated largely from Cepheid variables and other stellar indicators, with their measured radial velocities to test for a systematic relationship. He found an approximately linear correlation in which the radial velocity of a nebula increases with its distance, with a proportionality constant of about 500 km/s per megaparsec. This velocity–distance relation, now known as Hubble's law, provided the first observational evidence that the universe is expanding and became a cornerstone of modern cosmology.
Key findings
- Established an approximately linear relation between the distances of extra-galactic nebulae and their radial velocities (Hubble's law).
- Derived a proportionality constant (Hubble constant) of roughly 500 km/s/Mpc from the available data.
- Provided the first observational evidence for the recession of galaxies, supporting an expanding universe.
Subjects & keywords
Cite this paper
Edwin Hubble (1929). A Relation between Distance and Radial Velocity among Extra-Galactic Nebulae. Proceedings of the National Academy of Sciences. https://doi.org/10.1073/pnas.15.3.168
@article{hubble1929relation,
author = {Edwin Hubble},
title = {A Relation between Distance and Radial Velocity among Extra-Galactic Nebulae},
journal = {Proceedings of the National Academy of Sciences},
year = {1929},
doi = {10.1073/pnas.15.3.168},
url = {https://doi.org/10.1073/pnas.15.3.168}
}