Solar System Explained: Planets, Moons, Asteroids, and More
Planets, moons, comets, asteroids, and everything in our neighbourhood
Our solar system formed about 4.6 billion years ago from a collapsing cloud of gas and dust. The sun contains 99.8% of all the mass in the solar system. The eight planets range from Mercury, smaller than some moons, to Jupiter, which is so large that all other planets could fit inside it with room to spare. Beyond Neptune lies the Kuiper Belt, home to Pluto and thousands of icy bodies — and beyond that, the Oort Cloud, a vast sphere of cometary material that extends to about two light-years from the sun.
Astronomy: Aurora Borealis
Aurora Borealis An aurora (pl. aurorae or auroras) is a natural light display in Earth’s upper atmosphere caused by charged particles from the Sun colliding with atoms in the atmosphere.
Read commentary →Astronomy: Callisto
Callisto Callisto ( kə-LIST-oh) is the second-largest moon of Jupiter, after Ganymede. It is also the third-largest moon in the Solar System, following Ganymede and Saturn's moon Titan, and nearly as large as the planet Mercury.
Read commentary →Astronomy: Ceres
Ceres Ceres (minor-planet designation: 1 Ceres) is a dwarf planet in the main asteroid belt between the orbits of Mars and Jupiter. It was the first known asteroid, discovered on 1 January 1801 by Giuseppe Piazzi at Palermo Astronomical Observatory in Sicily, and announced as a new planet.
Read commentary →Astronomy: Charon
Charon Charon ( KAIR-on, -ən or SHARR-ən), formal designation (134340) Pluto I, is the largest of the five known natural satellites of the dwarf planet Pluto. It has a mean radius of 606 km (377 mi).
Read commentary →Astronomy: Chicxulub Impact
Chicxulub Impact The Chicxulub crater is an impact crater buried underneath the Yucatán Peninsula in Mexico. Its center is offshore, but the crater is named after the onshore community of Chicxulub Pueblo (not to be confused with the larger coastal town of Chicxulub Puerto).
Read commentary →Astronomy: Comet Hale-Bopp
Comet Hale-Bopp Comet Hale–Bopp (formally designated C/1995 O1) is a long-period comet that was one of the most widely observed of the 20th century and one of the brightest seen for many decades. Alan Hale and Thomas Bopp discovered Comet Hale–Bopp separately on July 23, 1995, before it became visible to the naked eye.
Read commentary →Astronomy: Comet NEOWISE
Comet NEOWISE C/2020 F3 (NEOWISE) or Comet NEOWISE is a long period comet with a near-parabolic orbit discovered on March 27, 2020, by astronomers during the NEOWISE mission of the Wide-field Infrared Survey Explorer (WISE) space telescope. At that time, it was an 18th-magnitude object, located 2.0 AU (300 million km; 190 million mi) away from the Sun and 1.7 AU (250 million km; 160 million mi) a
Read commentary →Astronomy: Deimos
Deimos Deimos () is the smaller and outer of the two natural satellites of Mars, the other being Phobos. Deimos has a mean radius of 6.2 km (3.9 mi) and takes 30.3 hours to orbit Mars.
Read commentary →Astronomy: Earth
Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. This is made possible by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water.
Read commentary →Astronomy: Enceladus
Enceladus Enceladus is the sixth-largest moon of Saturn and the 18th largest in the Solar System. It is about 500 kilometres (310 miles) in diameter, about a tenth of that of Saturn's largest moon, Titan.
Read commentary →Astronomy: Eris
Eris Eris (minor-planet designation: 136199 Eris) is the most massive and second-largest known dwarf planet in the Solar System. It is a trans-Neptunian object (TNO) in the scattered disk and has a high-eccentricity orbit.
Read commentary →Astronomy: Europa
Europa Europa ( ) is the smallest and least massive of Jupiter's four Galilean moons. It is observable from Earth with common binoculars and is a planetary-mass moon, slightly smaller and less massive than Earth's Moon.
Read commentary →Astronomy: Ganymede
Ganymede Ganymede is a natural satellite of Jupiter and is the largest and most massive moon in the Solar System. Like Saturn's largest moon Titan, it is larger than the planet Mercury, but has somewhat less surface gravity than Mercury, Io, or the Moon due to its lower density compared to the three.
Read commentary →Astronomy: Halley's Comet
Halley's Comet Halley's Comet is the only known short-period comet that is consistently visible to the naked eye from Earth, appearing every 72–80 years, though with the majority of recorded apparitions (25 of 30) occurring after 75–77 years. It last appeared in the inner parts of the Solar System in 1986 and will next appear in mid-2061.
Read commentary →Astronomy: Haumea
Haumea Haumea (minor-planet designation: 136108 Haumea) is a dwarf planet located beyond Neptune's orbit. It was discovered in 2004 by a team headed by Mike Brown of Caltech at the Palomar Observatory, and formally announced in 2005 by a team headed by José Luis Ortiz Moreno at the Sierra Nevada Observatory in Spain, who had discovered it that year in precovery images taken by the team in 2003.
Read commentary →Astronomy: Iapetus
Iapetus Iapetus () is the outermost of Saturn's large moons. With an estimated diameter of 1,469 km (913 mi), it is the third-largest moon of Saturn and the eleventh-largest in the Solar System.
Read commentary →Astronomy: Io
Io Io () is the innermost and second-smallest of the four Galilean moons of Jupiter. Slightly larger than Earth's Moon, Io is the fourth-largest natural satellite in the Solar System, has the highest density and strongest surface gravity of any natural satellite, and the lowest amount of water by atomic ratio of any known astronomical object in the Solar System.
Read commentary →Astronomy: Jupiter
Jupiter Jupiter is the fifth planet from the Sun, and the largest in the Solar System. It is a gas giant with a mass nearly 2.5 times that of all the other planets in the Solar System combined and slightly less than one-thousandth the mass of the Sun.
Read commentary →Astronomy: Lunar Eclipse
Lunar Eclipse A lunar eclipse, also called a blood moon, is an astronomical event that occurs when the Moon orbits through Earth's shadow. Lunar eclipses occur during eclipse season, when the Moon's orbital plane is approximately in line with Earth and the Sun. The type and length of a lunar eclipse depend on the Moon's proximity to the lunar node. In contrast with elusive and short-lasting s
Read commentary →Astronomy: Makemake
Makemake Makemake (minor-planet designation: 136472 Makemake) is a dwarf planet in the Kuiper belt, a disk of icy bodies beyond the orbit of Neptune. It is the fourth largest trans-Neptunian object and the largest member of the classical Kuiper belt, having a diameter 60% that of Pluto.
Read commentary →Astronomy: Mars
Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", for its orange-red appearance.
Read commentary →Astronomy: Mercury
Mercury Mercury is the first planet from the Sun and the smallest in the Solar System. It is a rocky planet with a trace atmosphere and a surface gravity slightly higher than that of Mars.
Read commentary →Astronomy: Meteor Showers
Meteor Showers A meteor shower is a celestial event in which a number of meteors are observed to radiate, or originate, from one point in the night sky. These meteors are caused by streams of cosmic debris called meteoroids entering Earth's atmosphere at extremely high speeds on parallel trajectories.
Read commentary →Astronomy: Mimas
Mimas Mimas is the seventh-largest natural satellite of Saturn. With a mean diameter of 396.4 kilometres or 246.3 miles, Mimas is the smallest astronomical body known to be roughly rounded in shape due to its own gravity.
Read commentary →Astronomy: Neptune
Neptune Neptune is the eighth and farthest known planet orbiting the Sun. It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet.
Read commentary →Astronomy: Perseid Meteor Shower
Perseid Meteor Shower The Perseids are a prolific meteor shower associated with the comet Swift–Tuttle that are usually visible from mid-July to late-August. The meteors are called the Perseids because they appear from the general direction of the constellation Perseus and in more modern times have a radiant bordering on Cassiopeia and Camelopardalis.
Read commentary →Astronomy: Phobos
Phobos Phobos () is the innermost and larger of the two natural satellites of Mars, the other being Deimos. The two moons were discovered in 1877 by American astronomer Asaph Hall.
Read commentary →Astronomy: Pluto
Pluto Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the Sun.
Read commentary →Astronomy: Saturn
Saturn Saturn is the sixth planet from the Sun and the second largest in the Solar System, after Jupiter. It is a gas giant, with an average radius of about 9 times that of Earth.
Read commentary →Astronomy: Solar Eclipse
Solar Eclipse A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring the view of the Sun from a small part of Earth, totally or partially. Such an alignment occurs approximately every six months, during the eclipse season in its new moon phase, when the Moon's orbital plane is closest to the plane of Earth's orbit.
Read commentary →Astronomy: Solar Wind
Solar Wind The solar wind is a stream of charged particles released from the Sun's outermost atmospheric layer, the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between 0.5 and 10 keV.
Read commentary →Astronomy: The Asteroid Belt
The Asteroid Belt The asteroid belt is a torus-shaped region in the Solar System, centered on the Sun and roughly spanning the space between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies called asteroids or minor planets.
Read commentary →Astronomy: The Kuiper Belt
The Kuiper Belt The Kuiper belt ( ) is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger—20 times as wide and 20–200 times as massive.
Read commentary →Astronomy: The Moon
The Moon The Moon is the only natural satellite of Earth. It orbits around Earth at an average distance of 384,399 kilometres (238,854 mi), a distance roughly 30 times the width of Earth.
Read commentary →Astronomy: The Oort Cloud
The Oort Cloud The Oort cloud (pronounced ORT or OORT), sometimes called the Öpik–Oort cloud, is theorized to be a cloud of billions of icy planetesimals surrounding the Sun at distances ranging from 2,000 to 200,000 AU (0.03 to 3.2 light-years). Its existence was proposed in 1950 by the Dutch astronomer Jan Oort, in whose honor the idea was later named.
Read commentary →Astronomy: The Sun
The Sun The Sun is the star located at the centre of the Solar System. It is a massive sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light and infrared radiation with 10% at ultraviolet energies.
Read commentary →Astronomy: The Tunguska Event
The Tunguska Event The Tunguska event was a large explosion of between three and 50 megatons TNT equivalent that occurred near the Podkamennaya Tunguska River in Yeniseysk Governorate (now Krasnoyarsk Krai), Russia, on the morning of 30 June 1908. The explosion over the sparsely populated East Siberian taiga felled a large number of trees, over an area of 2,150 km2 (830 sq mi) of forest, and eyew
Read commentary →Astronomy: Titan
Titan Titan is the largest moon of Saturn and the second-largest in the Solar System. It is the only moon known to have a dense atmosphere—denser than Earth's—and is the only known object in the Solar System besides Earth with clear evidence of stable bodies of surface liquid.
Read commentary →Astronomy: Triton
Triton Triton is the largest natural satellite of the planet Neptune. It is the only moon of Neptune massive enough to be rounded under its own gravity and hosts a thin, hazy atmosphere.
Read commentary →Astronomy: Uranus
Uranus Uranus is the seventh planet from the Sun. It is a gaseous cyan-coloured ice giant.
Read commentary →Astronomy: Venus
Venus Venus is the second planet from the Sun. Similar in size and mass to Earth, Venus has no liquid water, and its atmosphere is far thicker and denser than that of any other rocky body in the Solar System.
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How many planets are in the solar system?
There are eight recognized planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Pluto was reclassified as a dwarf planet in 2006 when the International Astronomical Union defined a planet as an object that has cleared its orbital neighborhood — which Pluto, sharing the Kuiper Belt with thousands of similar bodies, has not done. There are currently five recognized dwarf planets and astronomers believe there may be a ninth large planet in the outer solar system, though it has not yet been observed directly.