Everything about Ceres Dwarf Planet totally explained
Ceres (or as ), also designated
1 Ceres (see
minor planet names), is the smallest identified
dwarf planet in the
Solar System and the only one in the
asteroid belt. It was discovered on
January 1 1801, by
Giuseppe Piazzi, Instead of a star, Piazzi found a moving star-like object, which he first thought was a
comet. Piazzi observed Ceres a total of 24 times, the final time on
February 11, when illness interrupted his observations. He announced his discovery on
January 24,
1801 in letters to fellow astronomers, among them his compatriot
Barnaba Oriani of
Milan. He reported it as a comet but "since its movement is so slow and rather uniform, it has occurred to me several times that it might be something better than a comet". In Greece, it's called Δήμητρα (
Demeter), after the goddess Ceres' Greek equivalent; in English usage, Demeter is the name of an asteroid (
1108 Demeter). Due to its uncommon usage, there's no consensus as to the proper adjectival form of the name, although the
nonce forms Cerian and
Cerean have been used in fiction. Grammatically, the form
Cererean would be correct, derived from its
Latin genitive,
Cereris. Ceres'
astronomical symbol is a
sickle,, similar to
Venus' symbol which is the female gender symbol and Venus' hand mirror. The element
Cerium was named after Ceres. The element
Palladium was originally also named after Ceres, but the discoverer changed its name after Cerium was named. Palladium is named after asteroid
2 Pallas.
Status
The classification of Ceres has changed more than once and has been the subject of some disagreement.
Johann Elert Bode believed Ceres to be the "missing planet" he'd proposed to exist between
Mars and
Jupiter, at a distance of 419 million km (2.8
AU) from the Sun. writing "they resemble small stars so much as hardly to be distinguished from them, even by very good telescopes". As the first such body to be discovered, it was given the designation 1 Ceres under the modern system of
asteroid numbering. A proposal before the
International Astronomical Union for the
definition of a planet would have defined a planet as "a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (b) is in orbit around a star, and is neither a star nor a satellite of a planet". Had this resolution been adopted, it would have made Ceres the fifth planet in order from the Sun. However, it wasn't accepted, and in its place an alternate definition of "planet" came into effect as of
August 24,
2006: A planet is "a celestial body that's in orbit around the sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a ... nearly round shape, and has
cleared the neighborhood around its orbit." By this definition, Ceres isn't a planet (because it shares its orbit with the thousands of other asteroids in the
main asteroid belt), and is now classified as a "
dwarf planet" (along with Pluto and
Eris). The issue of whether Ceres remains an asteroid wasn't addressed. Dual classifications such as
Main-belt comets do exist, and being a dwarf planet doesn't preclude having dual designations.
Physical characteristics
Ceres is the largest object in the
asteroid belt, which lies between
Mars and
Jupiter.
The mass of Ceres has been determined by analysis of the influence it exerts on small asteroids. Results obtained by different authors are slightly different. The average of the three most precise values as of 2008 is approximately 9.4 kg. With this mass Ceres comprises about a third of the estimated total 3.0 ± 0.2 kg mass of the asteroids in the solar system, together totalling about 4% of the mass of the
Moon. Ceres' size and mass are sufficient to give it a nearly spherical shape.
3 Juno, and
4 Vesta are known to be quite irregular.
The surface composition of Ceres is broadly similar to that of
C-type asteroids. Sometimes Ceres is classified as
G-type asteroid.
Ultraviolet observations by
IUE spacecraft detected statistically significant
hydroxide water vapour near the Cererean north pole. its
oblateness appears too small for an undifferentiated body, which indicates that it consists of a rocky core overlain with an icy
mantle. This result is supported by the observations made by Keck telescope in 2002 and by evolutionary modelling.
Only a few features have been unambiguously detected on the surface of Ceres. High resolution
ultraviolet Hubble Space Telescope images taken in 1995 showed a dark spot on its surface which was nicknamed "Piazzi" in honour of the discoverer of Ceres. More recent visible light
Hubble Space Telescope images of a full rotation taken in 2003 and 2004 showed eleven recognizable surface features, the nature of which is currently unknown. One of these features corresponds to the "Piazzi" feature observed earlier. These groupings of asteroids share similar orbital elements, which may indicate a common origin through an asteroid collision some time in the past. Ceres, however, was found to have spectral properties different from other members of the family, and so this grouping is now called the
Gefion family, named after the lowest-numbered family member,
1272 Gefion.
Self rotation period of Ceres is 9 hours and 4 minutes.
Origin and evolution
The observations imply that Ceres is a remaining
protoplanet – planetary embryo, which formed 4.57 billion years ago in the
asteroid belt. While the majority of embryos (including all lunar- to Mars-sized bodies) were ejected from the
Solar System by
Jupiter or merged with other embryos to form
terrestrial planets, The ice on the surface gradually
sublimated leaving behind various hydrated minerals like
clays and
carbonates. This is generally regarded as being just barely too dim to be seen with the
naked eye, but under exceptional viewing conditions a very sharp-sighted person may be able to see this
dwarf planet. The only asteroids that can reach so bright a magnitude are
4 Vesta, and, during rare oppositions near perihelion,
2 Pallas and
7 Iris. At a
conjunction Ceres has a magnitude of around +9.3, which corresponds to the faintest objects visible with 10×50
binoculars. It can thus be seen with binoculars whenever it's above the horizon of a fully dark sky.
Some notable observation milestones for Ceres include:
- An occultation of a star by Ceres observed in Mexico, Florida and across the Caribbean on November 13 1984.
- Ultraviolet Hubble Space Telescope images with 50 km resolution taken in 1995.
- Infrared images with 30 km resolution taken with the Keck telescope in 2002 using adaptive optics.
- Visible light images with 30 km resolution (the best to date) taken using Hubble in 2003 and 2004. The spacecraft instrumentation includes a framing camera, a visual and infrared spectrometer, and a gamma-ray and neutron detector. These will be used to examine the dwarf planet's shape and element abundance.
Radio signals from spacecraft in orbit around Mars and on its surface have been used to estimate the mass of Ceres from the perturbations induced by it onto the motion of Mars.[Further Information]
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