VLT/SPHERE images of most asteroids > 210 km in diameter to scale. Deconvolved with MISTRAL algorithm. Main-belt asteroids > 200 km that were not imaged are (451) Patientia, (65) Cybele and (107) Camilla. Trojan (624) Hektor may also be in this size range.VLT/SPHERE images of a large number of asteroids 100 to 210 km in diameter, to scale. (10) Hygiea, (31) Euphrosyne and (8) Flora have collisional families; all three are round due to having re-coalesced after being disrupted.
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), whereas asteroids are mostly between 2–3 AU from the Sun or at the orbit of Jupiter 5 AU from the Sun. Also, 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.[1][2]
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.[9]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.[10]
Graphs are unavailable due to technical issues. There is more info on Phabricator and on MediaWiki.org.
Comparative masses of the asteroids with nominal masses > 20×1018 kg, assuming a total Main Belt mass of 2394×1018 kg. The mass of Herculina is particularly uncertain.
The proportions assume that the total mass of the asteroid belt is 2.39×1021 kg, or (12.4±1.0)×10−10M☉.[12]
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.[3][13][1]
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.[16] 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 case of 99942 Apophis, (152680) 1998 KJ9, (153814) 2001 WN5, and 367943 Duende) when the asteroid passes very close to Earth.
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).
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).
Minor planets with orbital inclinations greater than 90° (the greatest possible is 180°) orbit in a retrograde direction. As of March 2018[update], of the near-800,000 minor planets known, there are only 99 known retrograde minor planets (0.01% of total minor planets known).[19] 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.[20]
NEO that sometimes has the highest relative velocity to Earth (79 km/s) of known objects that come within 0.5 AU of Earth. However, the relative velocity at 1 AU from the sun is less than 72 km/s.
^ 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.
First main-belt asteroid discovered to have an inclination greater than 2 Pallas. Most highly inclined known main-belt asteroid from August 30, 1935, to June 14, 1980
First asteroid to rank greater than one on the Torino Scale (it was ranked at 2, then 4; now down to 0). Previously better known by its provisional designation 2004 MN4.
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.[26]
An object discovered March 18, 1892, by Max Wolf with provisional designation "1892 X" was named 330 Adalberta, but was lost and never recovered. In 1982 it was determined that the observations leading to the designation of 1892 X were stars, and the object never existed. The name and number 330 Adalberta was then reused for another asteroid discovered by Max Wolf on February 2, 1910, which had the provisional designation A910 CB.
The object A904 EB discovered March 14, 1904, by Max Wolf was named 525 Adelaide and was subsequently lost. Later, the object 1930 TA discovered October 3, 1930, by Sylvain Arend was named 1171 Rusthawelia. In those pre-computer days, it was not realized until 1958 that these were one and the same object. The name Rusthawelia was kept (and discovery credited to Arend); the name 525 Adelaide was reused for the object 1908 EKa discovered October 21, 1908, by Joel Hastings Metcalf.
The object 1911 LX discovered April 22, 1911, by H. E. Wood was named 715 Transvaalia. On April 23, 1920, the object 1920 GZ was discovered and named 933 Susi. In 1928 it was realized that these were one and the same object. The name Transvaalia was kept, and the name and number 933 Susi was reused for the object 1927 CH discovered February 10, 1927, by Karl Reinmuth.
The object A917 CB discovered February 13, 1917, by Max Wolf was named 864 Aase, and the object 1926 XB discovered December 7, 1926, by Karl Reinmuth was named 1078 Mentha. In 1958 it was discovered that these were one and the same object. In 1974, this was resolved by keeping the name 1078 Mentha and reusing the name and number 864 Aase for the object 1921 KE, discovered September 30, 1921, by Karl Reinmuth.
The object 1928 DC discovered February 24, 1928, by Karl Reinmuth was named 1095 Tulipa, and the object 1938 DO discovered February 20, 1938, by Yrjö Väisälä was named 1449 Virtanen. In 1966 it was discovered that these were one and the same object. The name 1449 Virtanen was kept and the name and number 1095 Tulipa was reused for the object 1926 GS discovered April 14, 1926, by Karl Reinmuth.
The object 1928 UF discovered October 25, 1928, by Zhang Yuzhe (Y. C. Chang) was named 1125 China, and was later lost. Later, the object 1957 UN1 was discovered on October 30, 1957, at Purple Mountain Observatory and was initially incorrectly believed to be the rediscovery of the object 1928 UF. The name and number 1125 China were then reused for the object 1957 UN1, and 1928 UF remained lost. In 1986, the object 1986 QK1 was discovered and proved to be the real rediscovery of 1928 UF. This object was given the new number and name 3789 Zhongguo. Note Zhongguo is the Mandarin Chinese word for "China", in pinyin transliteration.
The object 1914 UQ discovered April 20, 1914, by G. N. Neujmin was named 787 Moskva (and retains that name to this day). The object 1934 FD discovered on March 19, 1934, by C. Jackson was given the sequence number 1317. In 1938, G. N. Neujmin found that asteroid 1317 and 787 Moskva were one and the same object. The sequence number 1317 was later reused for the object 1935 RC discovered on September 1, 1935, by Karl Reinmuth; that object is now known as 1317 Silvretta.
Landmark names
Asteroids were originally named after female mythological figures. Over time the rules loosened.
First asteroid with non-Classical and non-Latinized name: 64 Angelina (in honor of a research station)
First asteroid with a non-feminine name: 139 Juewa (ambiguous) or 141 Lumen
First asteroid with a non-feminized man's name: 903 Nealley
Many landmark numbers had specially chosen names for asteroids, and there was some debate about whether Pluto should have received number 10000, for example. This list includes some non-asteroids.
Dictionary of Minor Planet Names, 5th ed.: Prepared on Behalf of Commission 20 Under the Auspices of the International Astronomical Union, Lutz D. Schmadel, ISBN3-540-00238-3
References
^ abcdefghijklmnopqrstuvwxyzaaabP. Vernazza et al. (2021) VLT/SPHERE imaging survey of the largest main-belt asteroids: Final results and synthesis. Astronomy & Astrophysics 54, A56
^As of Jan 2019, good rotational coverage (≥ 4 epochs) had also been obtained for 476 Hedwig and 596 Scheila.[1]
^ abcM. Pajuelo, Benoit Carry, Frédéric Vachier, Michael Marsset et al. (March 2018) Physical, spectral, and dynamical properties of asteroid (107) Camilla and its satellites, Icarus 309
^Berdeu, Anthony; Langlois, Maud; Vachier, Frédéric (February 2021). "First observation of a quadruple asteroid. Detection of a third moon around (130) Elektra with SPHERE/IFS". Astronomy & Astrophysics. 658: 21.
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