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List of exceptional asteroids

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List of exceptional asteroids

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.

Contents

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. 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.

Most massive

Below are the nineteen most massive measured asteroids. The masses of asteroids are calculated from perturbations caused by Mars and other asteroids, except in those that have been visited by spacecraft where a direct mass determination 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.

(All the data above are from Baer et al. 2011, apart from 48 Doris and 532 Herculina, which are Kochetova, 2004. The proportions assume that the total mass is 3.0×1021 kg, or 6991150000000000000♠(15.0±1.0)×10−10 M.

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 asteroids with an accurately measured mass, due to the fact that they have been (and are being) 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, 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.

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. 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 4123 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 0.027 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).

Retrograde

Minor planets with orbital inclinations greater than 90° (the greatest possible is 180°) orbit in a retrograde direction. As of September 2016, of the more than 700,000 minor planets known, there are only 95 known retrograde minor planets. 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.

^ 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.

Trojans

  • Earth trojans: 2010 TK7.
  • Mars trojans: (121514) 1999 UJ7, 5261 Eureka, (101429) 1998 VF31, (311999) 2007 NS2, (385250) 2001 DH47, 2011 SC191, 2011 UN63, and the candidate 2011 SL25.
  • Jupiter trojans: the first one was discovered in 1906, 588 Achilles, and the current total is over 6,000.
  • Numbered minor planets that are also comets

    The above table lists only numbered asteroids that are also comets. Note there are several cases where a non-numbered minor planets turned out to be a comet, e.g. C/2001 OG108 (LONEOS), which was provisionally designated 2001 OG108.

    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.

    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

    List of exceptional asteroids Wikipedia


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