Astronomy: Quick Facts

Written and fact-checked by

The Information Architects of Encyclopaedia Britannica

Last updated

Nov. 13, 2026

News •

A distant exoplanet mysteriously vanished from sight. Astronomers just discovered why • Nov. 10, 2026, 4:00 PM ET (Space)

Scientists May Have Discovered a Massive Starless Galaxy • Nov. 9, 2026, 6:15 AM ET (WIRED)

What ended the 'Cosmic Dark Age'? Astronomers say they're closer than ever to an answer. • Oct. 31, 2026, 11:00 AM ET (Live Science)

Astronomers found a mysterious object beyond Neptune, and it could be a new dwarf planet • Oct. 28, 2026, 3:00 AM ET (Space)

Record breaker! Astronomers spot powerful cosmic explosion that lasted 27 days • Oct. 26, 2026, 1:00 PM ET (Space)

Photos and Videos

Hubble Space Telescope

Irregularly shaped nickel-iron meteorite from Canyon Diablo, Arizona, with a dark, metallic, and slightly rusty surface.

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.

Diagram illustrating the Doppler shift in astronomy, showing how absorption lines in a color spectrum move toward violet for approaching objects and toward red for receding objects, with labeled comparison spectra.

Diagram of the solar system showing planetary orbits with the distance from Earth to the Sun labeled as 1 astronomical unit (AU), equal to about 149.6 million kilometers. Other planets' distances from the Sun in AU are also marked, illustrating how the AU is used to measure distances within the solar system.

solar system to scale

Brian May: Queen guitarist and astrophysicist

Learn more about the Nice model of solar system evolution and how samples brought back from the Moon fit within it

Five facts about solar eclipses

Kepler's revolutionary laws of planetary motion

How the big-bang theory was developed

See All Videos and Images →

Topics

galactic archaeology astrogeology telescope radar astronomy space exploration Cosmology Celestial mechanics Solar system Universe 10 Women Scientists Who Should Be More Famous chemistry Earth sciences physics metrology mathematics principles of physical science chemical element subatomic particle atom time

Dig Deeper: More Articles That Discuss This Topic

Key People

default image

Fred L. Whipple

American astronomer

Galileo

Galileo

Italian natural philosopher, astronomer, and mathematician

Johannes Kepler

Johannes Kepler

German astronomer

Nicolaus Copernicus

Nicolaus Copernicus

Polish astronomer

Giordano Bruno

Giordano Bruno

Italian philosopher

Engraving of six astronomers, with Hipparchus seated at center and, from left to right, Galileo, Johannes Hevelius, Tycho Brahe, Nicolaus Copernicus, and Ptolemy standing, each holding scientific instruments.

Hipparchus

Greek astronomer

William Herschel

William Herschel

British-German astronomer

Arthur Stanley Eddington.

Arthur Eddington

British scientist

Al-Bīrūnī, Afghan commemorative stamp, 1973.

al-Bīrūnī

Persian scholar and scientist

Engraving portrait of Carl Friedrich Gauss wearing a cap and formal 19th-century clothing, with detailed shading around his face and upper body.

Carl Friedrich Gauss

German mathematician

default image

Henry Norris Russell

American astronomer

How did Ptolemy explain retrograde motion?

Ptolemy

Egyptian astronomer, mathematician, and geographer

Painting of Danish astronomer Tycho Brahe wearing a black robe with a white ruffled collar and a gold chain necklace with a large pendant.

Tycho Brahe

Danish astronomer

Edmond Halley

Edmond Halley

British scientist

Edwin Hubble

Edwin Hubble

American astronomer

Sima Qian

Sima Qian

Chinese historian and scientist

Vera Rubin

Vera Rubin

American astronomer

default image

Sir William Rowan Hamilton

Irish mathematician and astronomer

Christiaan Huygens

Christiaan Huygens

Dutch scientist and mathematician

Friedrich Wilhelm Bessel

Friedrich Wilhelm Bessel

German astronomer

This artist's concept illustrates Kepler-16b, the first planet known to definitively orbit two stars -- what's called a circumbinary planet. The planet, which can be seen in the foreground, was discovered by NASA's Kepler mission. The two orbiting stars r

Extrasolar Planets

constellation virgo, astronomy

Constellations of the Zodiac and Their Signs Quiz

27 True-or-False Questions from Britannica’s Most Difficult Science Quizzes

36 Questions from Britannica’s Most Popular Science Quizzes

Nicolaus Copernicus. Nicolas Copernicus (1473-1543) Polish astronomer. In 1543 he published, forward proof of a Heliocentric (sun centered) universe. Coloured stipple engraving published London 1802. De revolutionibus orbium coelestium libri vi.

All About Astronomy

View of the Andromeda Galaxy (Messier 31, M31).

Astronomy and Space Quiz

Michael Faraday (L) English physicist and chemist (electromagnetism) and John Frederic Daniell (R) British chemist and meteorologist who invented the Daniell cell.

Faces of Science

Nicolaus Copernicus. Nicolas Copernicus (1473-1543) Polish astronomer. In 1543 he published, forward proof of a Heliocentric (sun centered) universe. Coloured stipple engraving published London 1802. De revolutionibus orbium coelestium libri vi.

All About Astronomy

Ursa major constellation illustration art. (Big Dipper) stars, space, night sky)

Stars: Explosions in Space