Notable asteroids & minor planets

Asteroids, also called minor planets, are small rocky bodies that are leftover material from the building of our solar system. Over 250,000 asteroids have been designated to date. Here are the brightest asteroids (listed by size) that can be viewed using a good pair of binoculars or a telescope. Magnitudes vary based on where the asteroid is located in its orbit:

Brightest asteroids

Common name Mean diameter Mass Magnitude range
Ceres (dwarf planet) 939 km 938x1018 kg 6.7 - 9.3
Pallas 512 km 204x1018 kg 6.5 - 10.6
Vesta 525 km 2.6x1018 kg 5.1 - 8.5
Hygiea (dwarf planet) 434 km 87x1018 kg 9.0 - 12
Eunomia 270 km 30x1018 kg 7.9 - 11.2
Juno 267 km 27x1018 kg 7.4 - 11.6
Bamberga 230 km 10x1018 kg 6.8 -
Iris 200 km 14x1018 kg 6.7 - 11.4
Hebe 190 km 12.5x1018 kg 7.5 - 11.5
Metis 180 km 9x1018 kg 8.1 - 11.8
Massalia 145 km 5.4x1018 kg 8.3 - 12
Melpomene 140 km 4x1018 kg 7.5 - 12
Flora 135 km 5x1018 kg 7.9 - 11.6
Nausikaa 95 km 1.8x1018 kg 8.2 -

Images of asteroids

Images of asteroids taken from planetary probes or research telescopes:

Asteroids are grouped according to their orbit range, as follows:

Near-Earth asteroids (NEAs)

Objects in near-earth orbit. There are about 9,000 objects known ranging from 1 meter to 32 meters in diameter. These asteroids can be further grouped as follows:

  • Atira group: Inside Earth's orbit; semi-major axis less than 1.0 AU
  • Aten group: Cross Earth's orbit; semi-major axis less than 1.0 AU
  • Apollo group: Cross Earth's orbit; semi-major axis greater than 1.0 AU
  • Amor group: Outside Earth's orbit; semi-major axis greater than 1.0 AU

Main-belt asteroids

The total mass of the asteroid belt is just 4% that of the moon. Millions of asteroids located between the orbits of Mars and Jupiter (1.8 to 4.0 AU) are in the "asteroid belt".

Trojan asteroids

Mainly, two large groups of asteroids located along the orbital path of Jupiter, 60 degrees ahead and behind the planet at the trojan points. There are also eight Mars Trojans and one Earth Trojan known.