Atlas · Small bodies

Asteroids and comets

More than a million and a half small bodies are known to orbit the Sun, and no drawing could hold them. So this chart does two things. It draws the real paths of 26 that are worth knowing by name, most of them because a spacecraft has been there. And it shows, as a count, where all the rest are.

Drawing I

Asteroids near the Earth

Six asteroids that spacecraft have visited or will soon watch closely, with the orbits of the Earth and Mars for scale. Four of them cross the Earth’s path on the page; their tilts mean they pass above or below it almost every time.

The drawing is 4.9 au across, which is 733 million km.

Drawing II

The asteroid belt

Nine asteroids of the main belt and Hektor, the largest Trojan, with Mars and Jupiter for scale. The faint band is where most of the belt lies. The belt is mostly empty space: spacecraft cross it without steering round anything.

The drawing is 11.5 au across, which is 1.72 billion km.

Drawing III

Comets that stay close

Six comets whose orbits take between three and seven years, with the Earth and Jupiter for scale. All but Encke swing out to about Jupiter’s distance: Jupiter’s pull is what holds this family of comets on such short orbits.

The drawing is 12.6 au across, which is 1.88 billion km.

Drawing IV

Out past the giant planets

Halley’s Comet, the centaur Chiron and Arrokoth in the Kuiper belt, with Jupiter, Saturn and Neptune for scale. The small square is the whole of drawing III. Halley goes round backwards, on a path tilted steeply against the planets’.

The drawing is 100 au across, which is 15 billion km.

Drawing V

Where the asteroids are

Every known asteroid with an orbit between 1.5 and 5.5 au, counted by the size of its orbit. The taller the line, the more asteroids have orbits of that size.

The belt is not even. It has gaps, marked in amber, at the orbits where an asteroid would keep step with Jupiter. The label 3:1 at 2.50 au means three orbits for each one of Jupiter’s. Jupiter’s pull, repeated at the same place every time, moves such asteroids away. In two places keeping step does the opposite and holds a group together: the Hildas at 3.97 au, and the Trojans, which share Jupiter’s own orbit.

Drawing VI

Beyond Neptune

The same count from 28 to 60 au: the Kuiper belt. Here keeping step with Neptune gathers bodies instead of clearing them. The spike at 39.4 au is the bodies that go round twice for every three of Neptune’s. Pluto is one of them. The belt thins out sharply past 47.7 au, where a body goes round once for every two of Neptune’s.

Only 7,013 bodies are counted here, against 1,465,477 in the asteroid belt. That is because they are far away and faint, not because they are few.

How to read it

In drawings I to IV you are looking straight down on the plane of the planets, from its north side. The Sun is the dot in the middle. Distances are to scale. The bodies are not: the largest asteroid drawn here would be far smaller than the width of a line.

A flat drawing cannot show tilt, so where two paths cross on the page the bodies are usually nowhere near each other. The tilt of each orbit is in the lists.

Drawings V and VI count what has been found. About 93 in every 100 known asteroids are in the main belt. Small, dark and distant bodies are hard to find, so the true numbers are larger everywhere, and far larger beyond Neptune.

Solid dot. A spacecraft has mapped all or nearly all of it.
Half dot. A spacecraft has flown past and seen part of it.
Ring. Never visited.
Pale line. Goes round the usual way, anticlockwise on these drawings.
Amber line. Goes round backwards. Halley’s Comet does.
Faint band. A belt of many small bodies, shown as the zone they keep to.

Where a comet is today is approximate. Gas streaming off a comet pushes it like a weak rocket, so its timing drifts from one orbit to the next. Each comet here is run forward from its last closest approach to the Sun, and its dot can be some way off. The asteroids’ dots are good to well within a line’s width.

One astronomical unit, written au, is the average distance from the Earth to the Sun: 149.6 million km. Touch a row in the lists to pick out its orbit.

Asteroids that come near the Earth

Small rocky bodies whose paths bring them into the Earth’s part of the Solar System. Being close, they are the ones spacecraft can reach and bring pieces back from.

Body	Orbit size	Nearest the Sun	One orbit	Tilt	Width	See it in 3D
Apophis. Seen only as a point of light.Will pass closer to the Earth than the weather satellites on 13 April 2029, and will not hit.	0.922 au	0.746 au	324 days	3.3°	0.3 km	Fly there
Bennu. Mapped by spacecraft.NASA's OSIRIS-REx spacecraft brought samples of it back to Earth in 2023.	1.13 au	0.897 au	1.2 years	6.0°	0.5 km	Fly there
Ryugu. Mapped by spacecraft.Japan's Hayabusa2 spacecraft brought samples of it back to Earth in 2020.	1.19 au	0.963 au	1.3 years	5.9°	0.9 km	Fly there
Itokawa. Mapped by spacecraft.Japan's Hayabusa spacecraft brought grains of it back to Earth in 2010.	1.32 au	0.953 au	1.52 years	1.6°	0.3 km	Fly there
Eros. Mapped by spacecraft.The first asteroid a spacecraft orbited and landed on: NEAR Shoemaker, in 2000 and 2001.	1.46 au	1.13 au	1.76 years	11°	16.8 km	Fly there
Didymos. Partly seen by spacecraft.In 2022 NASA's DART spacecraft struck its small moon, Dimorphos, on purpose, and changed that moon's orbit.	1.64 au	1.01 au	2.11 years	3.4°	0.8 km	Fly there

Asteroids of the main belt

The belt between Mars and Jupiter holds most of the known asteroids. Ceres, the largest body in it, counts as a dwarf planet and is on the chart of the Solar System.

Body	Orbit size	Nearest the Sun	One orbit	Tilt	Width	See it in 3D
Gaspra. Partly seen by spacecraft.The first asteroid a spacecraft flew past: Galileo, in 1991.	2.21 au	1.83 au	3.29 years	4.1°	12.2 km	Fly there
Vesta. Mapped by spacecraft.The second largest body in the asteroid belt. NASA's Dawn spacecraft orbited it in 2011 and 2012.	2.36 au	2.15 au	3.63 years	7.1°	523 km	Fly there
Lutetia. Partly seen by spacecraft.Photographed by the European spacecraft Rosetta as it flew past in 2010.	2.43 au	2.03 au	3.8 years	3.1°	98 km	Fly there
Mathilde. Partly seen by spacecraft.Photographed by NASA's NEAR Shoemaker spacecraft as it flew past in 1997.	2.65 au	1.95 au	4.31 years	6.7°	52.8 km	Fly there
Juno. Seen only as a point of light.The third asteroid ever found, in 1804.	2.67 au	1.99 au	4.37 years	13°	247 km	Fly there
Pallas. Seen only as a point of light.The third largest asteroid, on a steeply tilted orbit.	2.77 au	2.13 au	4.61 years	35°	513 km	Fly there
Ida. Partly seen by spacecraft.Photographed by NASA's Galileo spacecraft in 1993, which found it has a small moon, Dactyl.	2.86 au	2.73 au	4.85 years	1.1°	32 km	Fly there
Psyche. Seen only as a point of light.A metal-rich asteroid. NASA's Psyche spacecraft, launched in 2023, is on its way there.	2.93 au	2.53 au	5 years	3.1°	222 km	Fly there
Hygiea. Seen only as a point of light.The fourth largest asteroid.	3.15 au	2.81 au	5.59 years	3.8°	407 km	Fly there

Further out

A Trojan sharing Jupiter’s orbit, a centaur among the giant planets, and a small world of the Kuiper belt.

Body	Orbit size	Nearest the Sun	One orbit	Tilt	Width	See it in 3D
Hektor. Seen only as a point of light.The largest of the Trojans, the asteroids that share Jupiter's orbit.	5.28 au	5.15 au	12.1 years	18°	225 km	Fly there
Chiron. Seen only as a point of light.The first centaur found: a body that orbits among the giant planets. It sometimes shows a faint coma, as a comet does.	13.7 au	8.49 au	50.6 years	6.9°	166 km	Fly there
Arrokoth. Partly seen by spacecraft.The most distant body a spacecraft has visited: New Horizons flew past on 1 January 2019.	44.1 au	42.5 au	292 years	2.5°	not given	Fly there

Comets

Bodies of ice and dust on stretched orbits. Near the Sun the ice turns to gas and carries dust off with it, making the coma and tails. Their own jets push them about, so a comet’s place along its orbit is less sure than an asteroid’s.

Body	Orbit size	Nearest the Sun	One orbit	Tilt	Width	See it in 3D
Comet Encke. Seen only as a point of light.The comet with the shortest orbit of any bright one: a little over three years.	2.22 au	0.339 au	3.3 years	11°	4.8 km	Fly there
Comet Tempel 1. Partly seen by spacecraft.NASA's Deep Impact spacecraft fired a block of copper into it in 2005 to see what was underneath.	3.15 au	1.54 au	5.58 years	10°	6 km	Fly there
Comet Wild 2. Partly seen by spacecraft.NASA's Stardust spacecraft flew through its coma in 2004 and brought the dust back to Earth.	3.45 au	1.60 au	6.41 years	3.2°	4 km	Fly there
Comet 67P. Mapped by spacecraft.In full, Churyumov-Gerasimenko, after the two astronomers who found it. The European spacecraft Rosetta orbited it for two years from 2014 and set a lander, Philae, on it.	3.46 au	1.24 au	6.44 years	7.0°	3.4 km	Fly there
Comet Hartley 2. Partly seen by spacecraft.Photographed by NASA's Deep Impact spacecraft in 2010.	3.48 au	1.06 au	6.48 years	14°	1.6 km	Fly there
Comet Borrelly. Partly seen by spacecraft.Photographed by NASA's Deep Space 1 spacecraft in 2001.	3.61 au	1.31 au	6.85 years	29°	4.8 km	Fly there
Halley's Comet. Partly seen by spacecraft.The most famous comet, back about every 76 years. Five spacecraft met it in 1986.	17.9 au	0.575 au	75.9 years	162°	11 km	Fly there
Comet Hale-Bopp. Seen only as a point of light.One of the brightest comets of the last century, visible to the naked eye for a year and a half around 1997. Its orbit reaches about 354 au from the Sun, seven times as far as the widest drawing here, so it is in the list only.	177 au	0.891 au	2,360 years	89°	60 km	Fly there

Where this comes from

Orbit size is the average of a body’s nearest and furthest distance from the Sun. Tilt is measured from the plane of the Earth’s orbit, and above 90° means the body goes round backwards. Width is an average: none of these bodies is round, and where JPL gives only the lengths of a body’s three axes, the width here is their mean. “Not given” means JPL’s database has no width for it. The gaps and groups are placed by sum from the planets’ orbits, not read off the count.