(ORDO NEWS) — Pallas (lat.Pallas) – the second open asteroid B-class, a rare class of asteroids, included in the group of carbon asteroids, which accounts for about 7% of the entire mass of the asteroid belt that extends between Mars and Jupiter.
With a diameter of 512 kilometers, Pallas was originally considered a dwarf planet, but is no longer considered as such, because its shape is very different from the typically spherical shape of objects of this type.
- Aphelios: 3.412605509 a. e.
- Perihelion: 2.13060671 AU e.
- Eccentricity: 0.23127363
- Orbital period: 4.62 years (1686.3 days)
- Equatorial rotation speed: 65 m / s
- Average orbital speed: 17.65 km / s
- Average proper movement: 78.041654 degrees / year
- Dimensions: 550 ± 8 × 516 ± 6 × 476 ± 6 km
- Volume: 7.1 ± 0.3 × 107 cubic kilometers
- Mass: 2.11 ± 0.26 × 1020 kilograms
- Surface area: 8.3 ± 0.2 × 105 square kilometers
- Average density: 3.0 ± 0.5 grams / cubic centimeter
- Escape speed: ≈ 0.33 km / s
- Apparent magnitude: ranges from 6.49 to 10.65
- Satellites: no
Although on average Pallas is much farther from Earth and has a much lower albedo (a characteristic of surface reflectivity) than asteroid Vesta, its average value in opposition can reach + 8.0, which puts it in the brightness range that can be observed with binoculars 10 × 50 (10x magnification, objective lens diameter (aperture) 50 mm).
As you move away from the Earth, the brightness of Pallas can drop to +10.6, which means that a telescope of at least an average size will be required to observe the asteroid. However, the brightness of Pallas can increase to about +6.4 or even brighter during some rare perihelion oppositions; One such event occurred in February 2014, when it shone at magnitude +6.96.
While this by no means can be asserted with certainty, some researchers believe that Pallas underwent at least some thermal changes and subsequent partial differentiation (partial division into several parts). If so, then Pallas is most likely a remnant of a protoplanet that failed to gain enough mass to become a full-size planet.
Current models describing planetary formation suggest that objects the size of Pallas and Vesta may have formed in the solar system in large numbers, but most of them were destroyed in the course of incessant collisions with protoplanets of similar size.
Is Pallas Really a Protoplanetary Remnant? It is unlikely that an answer will be received in the near future, since at present no space agency plans to study the asteroid at close range.
Because Pallas’s orbit is unusually tilted to the ecliptic and nearly as eccentric as Pluto’s, the asteroid is out of reach of spacecraft. Consequently, the asteroid can only be studied using spectroscopic analysis, and the existing relatively detailed images were obtained during the NASA Dawn mission and “cursory surveys” from the NASA / ESA Hubble Space Telescope.
However, spectroscopic analysis showed that Pallida’s surface is composed primarily of silicate, including trace amounts of water and iron. Silicates of this type are usually a mixture of pyroxene and olivine, which are found in carbonaceous chondritic meteorites, although the amount of water minerals in these meteorites is usually lower than in chondritic CM-type meteorites *.
* CM- type meteorites are named after the Migiei meteorite that fell in the village of Migiei, Ukraine, in 1889. This type of meteorite usually contains about 10% water and many complex organic compounds. In fact, one example of a CM-type meteorite, the Murchison meteorite that fell in Murchison, Australia in 1969, was found to contain over 230 different amino acids. Since only 20 amino acids are found naturally on Earth, most researchers believe that the organic material in CM-type meteorites is primitive interstellar material formed outside the solar system.
Although Pallas is the largest known asteroid in the solar system after Ceres and Vesta, it is the only one of these large asteroids that has not been visited by a spacecraft. This, as mentioned above, is due to its orbit, which has an unusually large inclination to the plane of the Earth’s orbit, which means that it is very difficult to get the probe into its orbit.
Available images show that the surface of Pallas has very interesting topographic features, suggesting a tough collision history. In both hemispheres of Pallas, numerous large craters have been found covering a surface that resembles a golf ball.
Two separate large impact pools on its surface can be associated with powerful impacts that split the original object into several separate bodies.
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