The following is a collection of lists of asteroids of the Solar System that are exceptional in some way, such as their size or orbit. For the purposes of this article, "asteroid" refers to minor planets out to the orbit of Neptune, and includes the dwarf planet Ceres, the Jupiter trojans and the centaurs, but not trans-Neptunian objects (objects in the Kuiper belt, scattered disc or inner Oort cloud). For a complete list of minor planets in numerical order, see List of minor planets. Asteroids are given minor planet numbers, but not all minor planets are asteroids. Minor planet numbers are also given to objects of the Kuiper belt, which is similar to the asteroid belt but farther out (around 30–60 AU). Asteroids are mostly between 2–3 AU from the Sun or at the orbit of Jupiter, 5 AU from the Sun. Comets are not typically included under minor planet numbers, and have their own naming conventions. Asteroids are given a unique sequential identifying number once their orbit is precisely determined. Prior to this, they are known only by their systematic name or provisional designation, such as 1950 DA.
Physical characteristics
Largest by diameter Estimating the sizes of asteroids from observations is difficult due to their irregular shapes, varying albedo, and small angular diameter. Observations by the Very Large Telescope of most large asteroids were published 2019–2021.
The number of bodies grows rapidly as the size decreases. Based on IRAS data there are about 140 main-belt asteroids with a diameter greater than 120 km, which is approximately the transition point between surviving primordial asteroids and fragments thereof. For a more complete list, see List of Solar System objects by size. The inner asteroid belt (defined as the region interior to the 3:1 Kirkwood gap at 2.50 AU) has few large asteroids. Of those in the above list, only 4 Vesta, 19 Fortuna, 6 Hebe, 7 Iris and 9 Metis orbit there. (Sort table by mean distance.)
Most massive Below are the sixteen most-massive measured asteroids. Ceres, at a third the estimated mass of the asteroid belt, is half again as massive as the next fifteen put together. The masses of asteroids are estimated from perturbations they induce on the orbits of other asteroids, except for asteroids that have been visited by spacecraft or have an observable moon, where a direct mass calculation is possible. Different sets of astrometric observations lead to different mass determinations; the biggest problem is accounting for the aggregate perturbations caused by all of the smaller asteroids.
The proportions assume that the total mass of the asteroid belt is 2.39×1021 kg, or (12.4±1.0)×10−10 M☉. Outside the top four, the ranking of all the asteroids is uncertain, as there is a great deal of overlap among the estimates. The largest asteroids with an accurately measured mass, because they have been studied by the probe Dawn, are 1 Ceres with a mass of (939.3±0.5)×1018 kg, and 4 Vesta at (259.076±0.001)×1018 kg. The third-largest asteroid with an accurately measured mass, because it has moons, is 87 Sylvia at (14.76±0.06)×1018 kg. Other large asteroids with masses measured from their moons are 107 Camilla and 130 Elektra. For a more complete list, see List of Solar System objects by size. Other large asteroids such as 423 Diotima currently only have estimated masses.
Brightest from Earth Only Vesta is regularly bright enough to be seen with the naked eye. Under ideal viewing conditions with very dark skies, a keen eye might be able to also see Ceres, as well as Pallas and Iris at their rare perihelic oppositions. The following asteroids can all reach an apparent magnitude brighter than or equal to the +8.3 attained by Saturn's moon Titan at its brightest, which was discovered 145 years before the first asteroid was found owing to its closeness to the easily observed Saturn. None of the asteroids in the outer part of the asteroid belt can ever attain this brightness. Even Hygiea and Interamnia rarely reach magnitudes of above 10.0. This is due to the different distributions of spectral types within different sections of the asteroid belt: the highest-albedo asteroids are all concentrated closer to the orbit of Mars, and much lower albedo C and D types are common in the outer belt. Those asteroids with very high eccentricities will only reach their maximum magnitude rarely, when their perihelion is very close to a heliocentric conjunction with Earth, or (in the cases of 433 Eros, 99942 Apophis, (152680) 1998 KJ9, (153814) 2001 WN5, and 367943 Duende) when the asteroid passes very close to Earth.
* Apophis will only achieve that brightness on April 13, 2029. It typically has an apparent magnitude of 20–22.
Slowest rotators
This list contains the slowest-rotating known minor planets with a period of at least 1000 hours, or 412⁄3 days, while most bodies have rotation periods between 2 and 20 hours. Also see Potentially slow rotators for minor planets with an insufficiently accurate period (U < 2).
Fastest rotators
This list contains the fastest-rotating minor planets with a period of less than 100 seconds, or 0.0277 hours. Bodies with a highly uncertain period, having a quality of less than 2, are highlighted in dark-grey. The fastest rotating bodies are all unnumbered near-Earth objects (NEOs) with a diameter of less than 100 meters (see table). Among the numbered minor planets with an unambiguous period solution are (459872) 2014 EK24, a 60-meter sized stony NEO with a period of 352 seconds, as well as (335433) 2005 UW163 and (60716) 2000 GD65, two main-belt asteroids, with a diameter of 0.86 and 2.25 kilometers and a period of 1.29 and 1.95 hours, respectively (see full list).
Orbital characteristics
Retrograde Minor planets with orbital inclinations near or greater than 90° (the greatest possible is 180°) orbit in a retrograde direction. As of March 2018, of the near-800,000 minor planets known, there are only 99 known retrograde minor planets (0.01% of total minor planets known). In comparison, there are over 2,000 comets with retrograde orbits. This makes retrograde minor planets the rarest group of all. High-inclination asteroids are either Mars-crossers (possibly in the process of being ejected from the Solar System) or damocloids. Some of these are temporarily captured in retrograde resonance with the gas giants.
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