Star

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

Open cluster NGC 290

imaging using ultraviolet light

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

Diagram illustrating how astronomers calculate the distance to a star using parallax: Earth is shown in two positions on opposite sides of its orbit around the Sun, with lines extending to a nearby star X and further to distant background stars. The apparent shift in star X's position, measured as angle A, is used to determine its distance, with the baseline labeled as 186,000,000 miles.

Night sky view of the constellation Orion, with three bright stars in a straight line forming Orion's Belt and a faint pink glow of the Orion Nebula below the belt.

illustration depicting the light curve of Algol

extrasolar planet Kepler-16b

Fomalhaut and dust belt

At a Glance

Cepheid variables

Star: Media

astronomy

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

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

Overview of several types of stars, notably the red dwarf, red giant, supergiant,...

Video: © Open University (A Britannica Publishing Partner)

$Understand how diffraction of light affects stellar images$

Understand how diffraction of light affects stellar images

Learn how diffraction affects stellar images.

Video: © MinutePhysics (A Britannica Publishing Partner)

Learn about Subrahmanyan Chandrasekhar's elucidation in understanding black holes

Learn about Subrahmanyan Chandrasekhar's elucidation in understanding black holes

An overview of Subrahmanyan Chandrasekhar's contribution to the understanding of...

Video: © Open University (A Britannica Publishing Partner)

Know about the various methods used to discover numerous exoplanets

Know about the various methods used to discover numerous exoplanets

Learn about the techniques used to detect extrasolar planets.

Video: © MinutePhysics (A Britannica Publishing Partner)

Know about the various historical supernovae - GRB 111209A, V838 Monocerotis, N 63A, and SN 1006

Know about the various historical supernovae - GRB 111209A, V838 Monocerotis, N 63A, and SN 1006

A discussion of various historical supernovae.

Video: © Open University (A Britannica Publishing Partner)

Explore exoplanets and the techniques used to detect them

Explore exoplanets and the techniques used to detect them

Learn about extrasolar planets (exoplanets) and the techniques used to detect them.

Video: © Massachusetts Institute of Technology (A Britannica Publishing Partner)

Discover how the Gaia satellite helps map the stars in space

Discover how the Gaia satellite helps map the stars in space

Overview of a plan for the Gaia satellite to take a “census” of stars, film 2013.

Video: © Open University (A Britannica Publishing Partner)

What are the three types of galaxies?

What are the three types of galaxies?

Learn about the three general types of galaxies: spiral, elliptical, and irregular.

Video: © Open University (A Britannica Publishing Partner)

Simple chalk-style diagram showing a person standing on Earth, surrounded by stars and arrows pointing outward, illustrating why the night sky appears dark.

Why Is It Dark at Night?

Infrared energy from stars causes space and the night sky to appear dark.

Video: © MinutePhysics (A Britannica Publishing Partner)

Listen to astrophysicist Neil deGrasse Tyson narrate a brief history of the formation of the universe, from the big bang to the present

Listen to astrophysicist Neil deGrasse Tyson narrate a brief history of the formation of the universe, from the big bang to the present

Astrophysicist Neil deGrasse Tyson narrating a brief history of the universe, from...

Video: © MinutePhysics (A Britannica Publishing Partner)

View an animation to understand the difference between supernovae and neutron stars

View an animation to understand the difference between supernovae and neutron stars

An overview of supernovae and neutron stars.

Video: © Open University (A Britannica Publishing Partner)

Diagram of the Milky Way galaxy showing labeled locations of the Sun, Milky Way center, Sagittarius dwarf elliptical, and Canis Major dwarf, with axes marking 80,000 light-years.

The Scale of the Universe: Earth's Solar System and Beyond

How big is our world?

Video: Encyclopædia Britannica, Inc.

Images

Open cluster NGC 290

Open cluster NGC 290

Stars in the open cluster NGC 290, as seen by the Hubble Space Telescope.

European Space Agency and NASA

imaging using ultraviolet light

imaging using ultraviolet light

The Sun as imaged in extreme ultraviolet light by the Earth-orbiting Solar and Heliospheric...

NASA

solar flare

solar flare

One of the strongest solar flares ever detected, in an extreme ultraviolet (false-colour)...

SOHO/ESA/NASA

Diagram illustrating how astronomers calculate the distance to a star using parallax: Earth is shown in two positions on opposite sides of its orbit around the Sun, with lines extending to a nearby star X and further to distant background stars. The apparent shift in star X's position, measured as angle A, is used to determine its distance, with the baseline labeled as 186,000,000 miles.

stellar distances

Calculating stellar distances.

Encyclopædia Britannica, Inc.

Sirius

Sirius

Sirius A and B (lower left) photographed by the Hubble Space Telescope. Sirius A...

NASA, ESA, H. Bond (STScI), and M. Barstow (University of Leicester)

Night sky view of the constellation Orion, with three bright stars in a straight line forming Orion's Belt and a faint pink glow of the Orion Nebula below the belt.

Orion

The constellation Orion is one of the easiest to recognize because of a group of...

peresanz/Shutterstock.com

illustration depicting the light curve of Algol

illustration depicting the light curve of Algol

Light curve of Algol (Beta Persei), an eclipsing variable, or eclipsing binary, star...

Encyclopædia Britannica, Inc.

extrasolar planet Kepler-16b

extrasolar planet Kepler-16b

The first planet found to orbit two stars, Kepler-16b (artist's conception).

T. Pyle—JPL-Caltech/NASA

Fomalhaut and dust belt

Fomalhaut and dust belt

The infrared emission from the young star Fomalhaut and the dust belt surrounding...

ESA/Herschel/PACS/Bram Acke, KU Leuven, Belgium

brown dwarf 2MASSWJ 1207334−393254

brown dwarf 2MASSWJ 1207334−393254

The brown dwarf 2MASSWJ 1207334−393254 (centre) as seen in a photo taken by the Very...

ESO

A Hertzsprung-Russell diagram plotting stars by absolute magnitude and spectral type, showing regions for main sequence stars, white dwarfs, giants, and supergiants, with color gradients from blue (hot and bright) to red (cool and dim). The Sun is marked along the main sequence.

Hertzprung-Russell diagram

The Hertzsprung-Russell diagram plots stars by absolute magnitude and spectral type....

Encyclopædia Britannica, Inc.

A Hertzsprung-Russell diagram plots absolute visual magnitude against color index for Population II stars in a globular cluster, highlighting regions for horizontal branch, red giants, lower main sequence, blue stragglers, and the RR Lyrae gap. Spectral classes B through M are marked along the top axis.

Hertzsprung-Russell diagram

Colour-magnitude (Hertzsprung-Russell) diagram for an old globular cluster made up...

Encyclopædia Britannica, Inc.

Small Magellanic Cloud

Small Magellanic Cloud

Infant stars in the Small Magellanic Cloud.

A. Nota–ESA/NASA

Pleiades

Pleiades

Bright nebulosity in the Pleiades (M45, NGC 1432), distance 490 light-years. Cluster...

Courtesy of Palomar Observatory/California Institute of Technology

Cepheid variables

Cepheid variables

Cepheid variables, as seen by the Hubble Space Telescope.

NASA-HQ-GRIN

supernova 1987A

supernova 1987A

Supernova 1987A in the Large Magellanic Cloud.

Jason Pun (NOAO) and SINS Collaboration

supernova

supernova

Three distant Type Ia supernovas, as observed by the Hubble Space Telescope in 1997....

P. Garnavich (Harvard-Smithsonian Center for Astrophysics) and NASA

Eta Carinae

Eta Carinae

The hourglass and disk shapes of the gas and dust clouds, as well as various smaller...

Photo AURA/STScI/NASA/JPL (NASA photo # STScI-PRC96-23a)

limb darkening in the Sun

limb darkening in the Sun

Limb darkening on the disk of the Sun. The planet Mercury can be seen as a small...

Mila Zinkova

Diagram illustrating stellar evolution, showing how stars form from a nebula, then follow different paths based on mass: low- and medium-mass stars become red giants, then planetary nebulae, and end as white dwarfs; high-mass stars become red supergiants, explode as supernovae, and end as either neutron stars or black holes.

stellar evolution

Stellar evolution.

Encyclopædia Britannica, Inc.

Orion Nebula (M42)

Orion Nebula (M42)

Centre of the Orion Nebula (M42). Astronomers have identified some 700 young stars...

NASA, C.R. O'Dell and S.K. Wong (Rice University)

W5 Star Formation Region

W5 Star Formation Region

The W5 Star Formation Region in an image taken by the Spitzer Space Telescope.

L. Allen and X. Koenig (Harvard Smithsonian CfA)—JPL-Caltech/NASA

A timeline diagram illustrates the life cycle of a medium-sized star, showing its progression from a cloud of hydrogen and dust, to a main-phase star like the Sun, then to a red giant, and finally collapsing into a white dwarf, with each stage labeled and depicted by a glowing sphere.

evolution of a Sun-like star

Evolution of a Sun-like star.

Encyclopædia Britannica, Inc.

Crab pulsar

Crab pulsar

Crab pulsar (NP 0532), as observed by the Hubble Space Telescope. The pulsar is the...

Photo AURA/STScI/NASA/JPL (NASA photo # STScI-PRC96-22a)

pulsar

A pulsar emits two beams of electromagnetic radiation along its magnetic axis. If...

© Merriam-Webster Inc.

black hole in M87

black hole in M87

Black hole at the center of the massive galaxy M87, about 55 million light-years...

Event Horizon Telescope collaboration et al.

Photosphere of the Sun with limb darkening, image taken by the Solar and Heliospheric Observatory satellite, Oct. 29, 2003.

Photosphere of the Sun with limb darkening, image taken by the Solar and Heliospheric...

SOHO/NASA

The star-formation history of the Milky Way Galaxy.

The star-formation history of the Milky Way Galaxy.

Encyclopædia Britannica, Inc.

The habitable zones (green) for stars that are like the Sun (middle), hotter than the Sun (top), and cooler than the Sun (bottom). The red areas are those in which liquid surface water would be lost as a result of a runaway greenhouse effect, and the blue areas are those in which liquid surface water would be completely frozen.

The habitable zones (green) for stars that are like the Sun (middle), hotter than...

Kepler mission/Ames Research Center/NASA

Diagram illustrating stellar parallax, showing Earth at two points in its orbit around the Sun, with lines connecting each position to a distant star and forming an angle labeled p to represent the parallax shift.

Stellar parallax.

Encyclopædia Britannica, Inc.

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