Astrophysics (Index)About

asteroid

(minor planet without comet characteristics)

The term asteroid is used for minor planets in the asteroid belt, out to Jupiter's orbit. It is also used more generally: often to include minor planets closer to the Sun, such as those that are near-Earth objects, and sometimes to include centaurs, i.e., minor planets further out. Vulcanoids are a theoretical population of asteroids within the orbit of Mercury (which would be difficult to detect).

The first discovered asteroids were Ceres and Pallas (now designated 1 Ceres and 2 Pallas) in 1801, with the 15th discovered in 1851. The term asteroid means star-like: they appeared as points (unresolved) though they move like planets. Now a million have been identified, many by computer, and the population is estimated to be multiple millions. Among the largest are Juno (3 Juno), Vesta (4 Vesta) and Hygiea (10 Hygiea).

A diameter of 10 meters is often (but not always) used as the threshold between asteroid and meteoroid. Ceres, the largest in the asteroid belt, is near 1,000 km in diameter, the next largest with less than 600 km. Asteroids are generally classified by type of orbit and by spectrum.

Asteroids are useful for studying the solar system's history and planets: they are thought to be shards due to collisions of un-fully-formed planets. They show varying composition, including iron that suggests a piece of a rocky planet's core, as well as various other materials including complex molecules. In addition to studying them by telescope and space probe, they are studied through the meteorites that are evidently asteroid material. A number of space missions have studied asteroids during flybys, in some cases by a mission primarily to visit a planet. A few missions have been specifically to study asteroids and a few of those have carried material back to Earth for study.


(minor planets,solar system,object type)
Further reading:
https://en.wikipedia.org/wiki/Asteroid
https://astronomy.swin.edu.au/cosmos/a/asteroid
http://hyperphysics.phy-astr.gsu.edu/hbase/Solar/asteroid.html

Referenced by pages:
101955 Bennu
2010 TK7
ADAM
ADAM::THOR
asteroid belt
asteroid family
ATLAS survey
axisymmetric
binary minor planet (BMP)
Campo Imperatore Near-Earth Object Survey (CINEOS)
Catalina Sky Survey (CSS)
Ceres
Chicxulub crater
chondrite
collisional erosion
cosmic dust
Dawn
Deep Space 1 (DS1)
flyby
Galileo
halo orbit
Hayabusa2
interplanetary medium (IPM)
IRAS
Juno
Kirkwood gap
Kozai mechanism (ZLK)
Kuiper Belt (K Belt)
Lagrangian point
late heavy bombardment (LHB)
LINEAR
LONEOS
Lucy
Mars crosser (MC)
mass extinction
mass spectrometer
Maxwell-Boltzmann distribution
meteorite
meteoroid
minor planet
Minor Planet Center (MPC)
Moon formation
morphology
NEAR Shoemaker (NEAR)
near-Earth object (NEO)
Nearby Supernova Factory (NSNF)
NEAT
occultation observations
orbital resonance
OSIRIS-REx
Oumuamua
Palomar Transient Factory (PTF)
Planet Crossing Asteroid Survey (PCAS)
Planet Nine
planetary embryo
planetary science
planetesimal
planetoid
primordial black hole (PBH)
protoplanet
provisional designation
Psyche
Psyche
quasi-satellite
regolith
solar system
solar system object (SSO)
SPACEWATCH
SSSB (SB)
Stardust
supernova survey
Teegarden's Star
Titius-Bode law
Uppsala-ESO Survey of Asteroids and Comets (UESAC)
VERITAS
water (H2O)
Wide-field Infrared Survey Explorer (WISE)
Yarkovsky effect
Yarkovsky-O'Keefe-Radzievskii-Paddack effect (YORP)

Index