(1) Cérès

Physical characteristics

Mass and dimensions

With 950 km in diameter, Cérès is by far the largest object of the Ceinture of asteroids (the largest member of the belt after Cérès is Vesta and measures a little less than 600 km in its greater dimension).

The mass of Cérès was given by analyzing its influence on small asteroids. The value most often quoted is approximately 9.5 {{x10 20}} kg, Junon and Vesta is definitely more irregular.

Surface

The composition of the surface of Cérès is coarsely similar to that of the asteroids of the type C. Sometimes, Cérès is classified like a Astéroïde of the type G ^,. One of these zones corresponds to “Piazzi”

Orbits

Cérès follows a solar Orbite located between Mars and Jupiter, inside the principal Ceinture of asteroids, with a period 4.6 years. This orbit is moderately tilted (: 10.6° compared to the plan of the ecliptic , to compare with the 7° Mercury and the 17° of eccentric Pluto) and slightly (: 0.08; in comparison, the orbital eccentricity of Mars is worth: 0.09).

Origin and evolution

The observations suggest that Cérès is a surviving Protoplanète, a planetary embryo which was formed it there 4,57 billion years in the Ceinture of asteroids. While the majority of the protoplanètes were ejected Solar system by Jupiter or amalgamated with forming the telluric Planets. This process caused a Volcanisme water and a Tectonique, erasing many geological characteristics. However, because of fast exhaustion of the sources of heat, Cérès cooled. One generally regards that as too weak being perceived with the naked eye, but it is nevertheless possible for a person equipped with an excellent sight and under conditions of exceptional observation of perceiving dwarf planet. The only asteroids being able to reach such a magnitude are Vesta and, during rare Opposition S to their Périhélie, Pallas and Iris. With the conjunctions, Cérès reaches the magnitude of: +9.3, which corresponds to the least luminous objects which can be visible using Jumelles 10× 50. The dwarf planet can thus be seen with the binoculars as soon as it is above the horizon by one black night. Pallas and Iris are invisible with the binoculars by small elongations.

The following table summarizes the visibility of Cérès between 2006 and 2017.

History

Discovered

The idea that an unknown planet can exist between the orbits of Mars and Jupiter was proposed for the first time by Johann Elert Bode in 1768^,. In the place, it observed an object moving on the vault of heaven, which it initially believed to be a Comet. Piazzi observed Cérès 24 times, the last time on February 11th. January 24th, 1801, Piazzi announced its discovery by letters with several Italian colleagues, among whom Barnaba Oriani with Milan. It described it like a comet, but noticed that “since its movement is slow and uniform, it seemed to me on several occasions which it could be a question of something of better than a comet. In Greece, it is called Δήμητρα (Déméter), according to the name of the Greek goddess equivalent to Cérès. The first asteroids discovered have a astrological symbol and that of Cérès is a Faucille (), similar to the symbol of Venus ().

The chemical element Cérium (atomic number 58) was discovered in 1803 by Berzelius and Klaproth, working independently. Berzélius gave him the name of the asteroid. The palladium was also named according to Cérès in the beginning, but its discoverer changed his name after the Cerium had its final name; palladium refers to another asteroid, Pallas.

Observations

Among the historically outstanding observations of Cérès:

a Occultation of a star by Cérès was observed with the Mexico, in Florida and through the the Antilles on November 13rd, 1984.
Of the images in the Ultraviolet was taken by the Space telescope Hubble in 1995, with a resolution of 50 km^,.
Of the images in the Infra-red of a resolution of 30 km, taken by the telescope Keck in 2002 using an adaptive Optical .
the best resolution current (in November 2007) was obtained in 2003 and 2004 on images in visible light of a resolution of 30 km taken by Hubble. Among the instruments, the probe counts a camera, a infra-red Spectromètre and in the visible one, and a detector of gamma rays and Neutron S. They will be used to examine the form of Cérès and the abundance of its elements.

Radio signals of machines in orbit around Mars or on its surface were used to estimate the mass of Cérès starting from disturbance of the movement of Mars, writing that “they resemble so much small stars qi' it is difficult to make the difference, even with very good telescopes”. In time that first discovered asteroid, Cérès took retrospectively designation (1) Cérès in the modern system of classification of the asteroids in the years 1850^,. One of the proposals for definitions presented in front of the international astronomical Union for the definition of a planet (a body in hydrostatic balance orbiting a star and not being neither a star, nor a satellite) would have made of Cérès fifth planet starting from the Sun. This definition was not adopted. The final definition was announced on August 24th, 2006, adding that a planet was “to have cleaned its vicinity”. Cérès was then categorized like dwarf Planet.

See too

Internal bonds

Asteroid
Belt of asteroids
dwarf Planet

External bonds

References

Be-X-old: Цэрэра (карлікаваяплянэта) Simple: Ceres (dwarf planet) Zh-min-nan: 1 Ceres

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