Star - Black Holes, Gravity, Mass

star

Table of Contents

Introduction & Top Questions
General considerations
- The Sun as a point of comparison
  - Variations in stellar size
  - Stellar activity and mass loss
- Distances to the stars
  - Determining stellar distances
  - Nearest stars
- Stellar positions
  - Basic measurements
  - Stellar motions
Light from the stars
- Stellar magnitudes
  - Measuring starlight intensity
  - Stellar colours
  - Magnitude systems
  - Bolometric magnitudes
- Stellar spectra
  - Line spectrum
  - Spectral analysis
  - Classification of spectral types
- Bulk stellar properties
  - Stellar temperatures
  - Stellar masses
    - Visual binaries
    - Spectroscopic binaries
    - Eclipsing binaries
    - Binaries and extrasolar planetary systems
    - Mass extremes
  - Stellar radii
  - Average stellar values
- Stellar statistics
  - Hertzsprung-Russell diagram
  - Estimates of stellar ages
  - Numbers of stars versus luminosity
  - Mass-luminosity correlations
- Variable stars
  - Classification
  - Pulsating stars
  - Explosive variables
  - Peculiar variables
Stellar structure
- Stellar atmospheres
- Stellar interiors
  - Distribution of matter
  - Source of stellar energy
Star formation and evolution
- Birth of stars and evolution to the main sequence
- Subsequent development on the main sequence
- Later stages of evolution
  - Evolution of low-mass stars
  - Origin of the chemical elements
  - Evolution of high-mass stars
- End states of stars
  - White dwarfs
  - Neutron stars
  - Black holes

References & Edit History Related Topics

Images & Videos

Learn about the different types of stars categorized according to their mass and temperature - red dwarfs, red giants, supergiants, white, and brown dwarf stars

illustration depicting the light curve of Algol

For Students

star summary

Black holes

instar inStar formation and evolution

Written by Kenneth Brecher, John Donald Fernie•All

Fact-checked by The Editors of Encyclopaedia Britannica

Last Updated: Nov 22, 2024 • Article History

Key People:: Frank Schlesinger; Herbert Hall Turner; Edward Emerson Barnard; Henry Draper; William Herschel

Related Topics:: Sun; quasar; Shaula; Gacrux; double star

See all related content

News •

First Close Up Picture of Star Outside Our Galaxy Shows a Giant About to Blow • Nov. 21, 2024, 6:41 AM ET (New York Times)

Winnipeg Jets achieve best start in NHL history at 14-1-0 after beating Stars - The Athletic • Nov. 9, 2024, 9:05 PM ET (New York Times)

Black Hole Tears Star to Shreds, Unleashing Cosmic Shockwaves • Nov. 8, 2024, 10:09 PM ET (SciTechDaily)

If the core remnant of a supernova exceeds about two solar masses, it continues to contract. The gravitational field of the collapsing star is predicted to be so powerful that neither matter nor light can escape it. The remnant then collapses to a black hole—a singularity, or point of zero volume and infinite density hidden by an event horizon at a distance called the Schwarzschild radius, or gravitational radius. Bodies crossing the event horizon, or a beam of light directed at such an object, would seemingly just disappear—pulled into a “bottomless pit.”

black hole in M87Black hole at the center of the massive galaxy M87, about 55 million light-years from Earth, as imaged by the Event Horizon Telescope (EHT). The black hole is 6.5 billion times more massive than the Sun. This picture was the first direct visual evidence of a supermassive black hole and its shadow. The ring is brighter on one side because the black hole is rotating, and thus material on the side of the black hole turning toward Earth has its emission boosted by the Doppler effect. The shadow of the black hole is about five and a half times larger than the event horizon, the boundary marking the black hole's limits, where the escape velocity is equal to the speed of light. Created from data collected in 2017, this picture was released in 2019.

The existence of black holes is well established, both on a stellar scale, such as exists in the binary system Cygnus X-1, and on a scale of millions or billions of solar masses at the centre of some galaxies, such as M87. (See quasar.)

Lawrence Hugh Aller Eric J. Chaisson John Donald Fernie Kenneth Brecher