List of exceptional asteroids

Ceres is the largest and most massive asteroid and the only one that is a dwarf planet.

Vesta is the brightest and second-most-massive asteroid. It suffered a crust-penetrating impact approximately one billion years ago.^[1]

The following is a collection of lists of exceptional asteroids in the Solar System. For the purposes of this article 'asteroid' means minor planet up to the orbit of Jupiter, which includes the dwarf planet Ceres. For a complete list of minor planets in numerical order, see List of minor planets.

Note: each asteroid is given a unique sequential identifying number after its orbit is precisely determined. Prior to this, asteroids are known only by their systematic name or provisional designation, such as "1950 DA".

Largest by diameter

Estimating the sizes of asteroids from observations is difficult due to their irregular shapes, varying albedo (reflectivity), and small angular diameter. For example pure C-type asteroids are much darker than most. Asteroids with only one or two axes measured may have a falsely inflated geometric mean diameter if the unknown second and/or third axis is noticeably smaller than the primary axis. Asteroid 16 Psyche has an IRAS diameter of 253 km, yet has a more recent and accurate geometric mean of only 186 km.

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.^[2] 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.

Largest by mass

Below are the nineteen most-massive measured asteroids.^[3] The masses of asteroids are calculated from perturbations caused by Mars and other asteroids. 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.^[4]

The relative masses of the top twelve asteroids known,^[3] compared to the remaining mass of the asteroid belt.^[5]

1 Ceres   4 Vesta   2 Pallas   10 Hygiea   31 Euphrosyne   704 Interamnia

511 Davida   532 Herculina   15 Eunomia   3 Juno   16 Psyche   52 Europa   all others

(All the data above are from Baer et al. 2011, apart from 48 Doris and 532 Herculina, which are Kochetova, 2004.)

Significant uncertainties remain. For example, the uncertainty in the estimate of 31 Euphrosyne is enough for its low end to overlap with both 704 Interamnia and 511 Davida, which overlap each other and also with 532 Herculina, which overlaps with 15 Eunomia and 3 Juno. Juno barely overlaps 52 Europa, which in turn overlaps with 16 Psyche. That is, outside the top four, the order of all the asteroids is uncertain. However, none of the lesser asteroids, of which the most massive are thought to be 88 Thisbe (at 17–19×10¹⁸ kg), 7 Iris, 29 Amphitrite and 48 Doris (all in the range of ≈15×10¹⁸ kg), overlap with Europa or Psyche, so the first 12 asteroids in the chart above are likely to be the top dozen unless a hitherto unmeasured asteroid proves to be unexpectedly massive.

The largest asteroid with an accurately measured mass, due to the fact that it has been visited by the probe Dawn, is 4 Vesta at 259.076±0.001×10¹⁸ kg. The second-largest asteroid with an accurately measured mass, due to the fact that it has a moon, is 87 Sylvia at 14.78±0.06×10¹⁸ kg.

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.^[6][7]

Brightest from Earth

Only Vesta regularly attains a brightness sufficient to be visible to the naked eye. 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 distribution of spectral types within different sections of the asteroid belt being such that the highest-albedo asteroids are all concentrated closer to Mars, and much lower albedo C and D types being common in the outer belt.

Those asteroids with very high eccentricities will only reach their maximum magnitude on unusual occasions when their perihelion is very close to a heliocentric conjunction with Earth, or (in the case of 99942 Apophis) when the asteroid passes very close to Earth.

* Apophis will only achieve that brightness on April 13, 2029.^[8][9] It typically has an apparent magnitude of 20–22.

Retrograde and highly inclined

Minor planets with orbital inclinations greater than 90° (the greatest possible is 180°) orbit in a retrograde direction. As of February 2015, of the 670,000+ minor planets known, there are only 62 known retrograde minor planets.^[10] In comparison, there are over 1920 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.^[11]

^ the value given when the number of observations is multiplied by the observation arc; larger values are generally better than smaller values depending on residuals.

Landmark asteroids

Spacecraft targets

Numbered minor planets that are also comets

Note there are quite a few other cases where a non-numbered asteroid with only a systematic designation (such as 2001 OG108) turned out to be a comet (in this case C/2001 OG108 (LONEOS)). The above table lists only numbered asteroids that are also comets.

Minor planets that were misnamed and renamed

In earlier times, before the modern numbering and naming rules were in effect, asteroids were sometimes given numbers and names before their orbits were precisely known. And in a few cases duplicate names were given to the same object (with modern use of computers to calculate and compare orbits with old recorded positions, this type of error no longer occurs). This led to a few cases where asteroids had to be renamed.^[16]

Record-setting close approaches to Earth

Exceptionally slowly rotating objects

Rotation periods have been determined for only a small fraction of asteroids (from light curves or from radar studies). Most asteroids have rotation periods of less than 24 hours. There are 14 objects suspected of having a rotation period greater than 30 days (720 hours). Asteroids larger than 150 meters usually have rotation periods longer than 2 hours.

See also: Minor Planet Lightcurve Parameters

Fastest rotating objects

Asteroids smaller than 150 meters usually have rotation periods shorter than 2 hours.

See also

• Asteroid Redirect Mission (Includes a list of notable objects in the solar system)
• List of Solar System objects by size
• List of numbered Aten asteroids
• List of asteroids named after people
• List of asteroids named after places
• List of Apollo asteroids
• List of Amor asteroids
• Centaur (minor planet)
• Scattered disk objects
• List of asteroids with moons
• List of Mercury-crossing minor planets
• List of Venus-crossing minor planets
• List of Earth-crossing minor planets
• List of Mars-crossing minor planets
• List of Jupiter-crossing minor planets
• List of Saturn-crossing minor planets
• List of Uranus-crossing minor planets
• List of Neptune-crossing minor planets
• List of instrument-resolved minor planets
• List of meteor air bursts

Books

• Dictionary of Minor Planet Names, 5th ed.: Prepared on Behalf of Commission 20 Under the Auspices of the International Astronomical Union, Lutz D. Schmadel, ISBN 3-540-00238-3

References

External links

• Lists and plots: Minor Planets
• PDS Asteroid Data Archive
• SBN Small Bodies Data Archive
• NASA Near Earth Object Program
• Major News About Minor Objects