![]() Only Vesta is regularly bright enough to be seen with the naked eye. Other large asteroids such as 423 Diotima currently only have estimated masses. The third-largest asteroid with an accurately measured mass, because it has moons, is 87 Sylvia at (14.3 ☐.5) ×10 18 kg.įor a more complete list, see List of Solar System objects by size. 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 ☐.5) ×10 18 kg, and 4 Vesta at (259.076 ☐.001) ×10 18 kg. Outside the top four, the ranking of all the asteroids is uncertain, as there is a great deal of overlap among the estimates. The proportions assume that the total mass of the asteroid belt is 2.39 ×10 21 kg, or (12.4 ☑.0) ×10 −10 M ☉. Īsteroids with nominal mass > 10 ×10 18 kg Name 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 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. Ceres, at a third the estimated mass of the asteroid belt, is half again as massive as the next fifteen put together. (Sort table by mean distance.)īelow are the sixteen most-massive measured asteroids. Of those in the above list, only 4 Vesta, 19 Fortuna, 6 Hebe, 7 Iris and 9 Metis orbit there. The inner asteroid belt (defined as the region interior to the 3:1 Kirkwood gap at 2.50 AU) has few large asteroids. For a more complete list, see List of Solar System objects by size. ![]() ![]() Based on IRAS data there are about 140 main-belt asteroids with a diameter greater than 120 km. The number of bodies grows rapidly as the size decreases. Observations by the Very Large Telescope of most large asteroids were published 2019–2021. Physical characteristics Largest by diameter Įstimating the sizes of asteroids from observations is difficult due to their irregular shapes, varying albedo, and small angular diameter. Prior to this, they are known only by their systematic name or provisional designation, such as 1950 DA. Also, comets are not typically included under minor planet numbers, and have their own naming conventions.Īsteroids are given a unique sequential identifying number once their orbit is precisely determined. 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 and at the orbit of Jupiter 5 AU from the Sun. 5.3 Minor planets that were misnamed and renamedĪsteroids are given minor planet numbers, but not all minor planets are asteroids.5.2 Numbered minor planets that are also comets.4.3 Multiple systems resolved by telescope.4.2 Surface resolved by telescope or lightcurve.3.4 Record-setting close approaches to Earth.
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