Dwarf planet Ceres reaches opposition this year in the constellation of Taurus on December 18th. The largest member of the asteroid belt shines at magnitude 6.7 and is easy to find as is located only 17 degrees to the northeast of brilliant Jupiter. The brightest star in Taurus, first magnitude orange/red star Aldebaran is also close by.
This month presents a superb opportunity to catch a glimpse of Ceres. Although it never quite gets bright enough to be seen with the naked eye, the dwarf planet is at its brightest possible this month and an easy binocular or small telescope object. It is also fun to track Ceres as it moves quickly on its current retrograde motion through Taurus.
The Titius–Bode law (sometimes termed just Bode's law) was a hypothesis that is attributed to German astronomers Johann Elert Bode and Johann Daniel Titius in middle part of the 18th century. Although an extremely simple hypothesis in terms of mathematics, it predicted to a remarkable accuracy the distance from the Sun of all the known planets at that time. Sir William Herschel then discovery Uranus in 1781 which also fit to the hypothesis. However, the rule had one notable discrepancy; it predicted the existence of a then unknown celestial object between the orbits of Mars and Jupiter, at a distance of 2.8 AU from the Sun.
The idea of an undiscovered planet existing between the orbits of Mars and Jupiter was now given enough credit, that around the end of the 18th century a number of astronomers starting systematically searching the skies for it. On January 1, 1801, Giuseppe Piazzi an Italian Catholic priest, mathematician, and astronomer discovered Ceres at the Academy of Palermo, Sicily. Originally he though it was a comet but soon realized that the object displayed no cometary activity. Once the orbit was calculated, it was determined that Ceres was located 2.77 AU from the Sun, almost exactly that distance predicted by the Titius–Bode law. The missing object had been found and Ceres was hailed as the new planet.
Ceres has a diameter of 975 kilometres (610 miles), which is much smaller than all the other planets. It was assigned a planetary symbol, and remained listed as a planet in astronomy books and tables for about half a century. During this time asteroids Pallas, Juno and Vesta were discovered and also classified as planets. Further discoveries followed and it soon became clear that many medium/small objects in the region between Mars and Jupiter existed and so they were all re-classified as asteroids. The region is now referred to as the asteroid belt. Incidentally, the Titius–Bode law was finally discredited in 1846 when the planet Neptune was discovered in a region of the solar system that was not at all predicted by the equations.
Despite its small diameter, Ceres is by far the largest of all objects in the asteroid belt and constitutes a third of the mass of the belt. In 2006, the International Astronomical Union (IAU) demoted Pluto as a planet and defined a new type of object, the "dwarf planet". Ceres was redefined for a third time as a dwarf planet along with Eris, Haumea, Makemake and Pluto. The latter are all Kuiper belt objects located in the outer regions of the solar system, with Ceres been the only dwarf plant located in the inner solar system and the asteroid belt.
Ceres has an apparent magnitude ranging from 6.7 to 9.3, and therefore is not a naked eye object even when at it's brightest. The dwarf planet is at its very best when opposition occurs close to perihelion, and on December 18, 2012 that is what exactly happens. On this date, Ceres will peak at magnitude 6.7 and hence easily visible in binoculars and small telescopes. Although it's the largest object in the asteroid belt, Ceres is not the brightest. That distinction goes to Vesta, which can reach magnitude 5 and hence naked eye visibility. Incidentally Vesta also reaches opposition this month, peaking at magnitude 6.4.
The beautiful zodiac constellation of Taurus is where to find Ceres in December. The famous constellation represents the head and shoulders of a bull, depicted as charging at neighbouring Orion. Aldebaran denotes the magnificent red eye of the bull with Ceres located in the northeast corner of the constellation about 18 degrees from Aldebaran. Unmistakable Jupiter is a few degrees north of Aldebaran.
Ceres Data Table
|Date||RA (J2000)||DEC (J2000)||Apparent Magnitude|
|November 26,2012||06h 06m 02s||23d 48m 11s||7.4|
|November 27,2012||06h 05m 18s||23d 52m 11s||7.4|
|November 28,2012||06h 04m 32s||23d 56m 11s||7.3|
|November 29,2012||06h 03m 45s||24d 00m 11s||7.3|
|November 30,2012||06h 02m 57s||24d 04m 13s||7.3|
|December 01,2012||06h 02m 07s||24d 08m 14s||7.3|
|December 02,2012||06h 01m 17s||24d 12m 16s||7.2|
|December 03,2012||06h 00m 24s||24d 16m 18s||7.2|
|December 04,2012||05h 59m 31s||24d 20m 20s||7.2|
|December 05,2012||05h 58m 36s||24d 24m 21s||7.2|
|December 06,2012||05h 57m 41s||24d 28m 22s||7.1|
|December 07,2012||05h 56m 44s||24d 32m 22s||7.1|
|December 08,2012||05h 55m 47s||24d 36m 21s||7.1|
|December 09,2012||05h 54m 48s||24d 40m 19s||7.0|
|December 10,2012||05h 53m 49s||24d 44m 15s||7.0|
|December 11,2012||05h 52m 49s||24d 48m 10s||7.0|
|December 12,2012||05h 51m 48s||24d 52m 04s||6.9|
|December 13,2012||05h 50m 47s||24d 55m 55s||6.9|
|December 14,2012||05h 49m 45s||24d 59m 45s||6.9|
|December 15,2012||05h 48m 42s||25d 03m 33s||6.8|
|December 16,2012||05h 47m 40s||25d 07m 18s||6.8|
|December 17,2012||05h 46m 37s||25d 11m 01s||6.8|
|December 18,2012||05h 45m 33s||25d 14m 41s||6.7|
|December 19,2012||05h 44m 30s||25d 18m 18s||6.7|
|December 20,2012||05h 43m 27s||25d 21m 53s||6.8|
|December 21,2012||05h 42m 23s||25d 25m 25s||6.8|
|December 22,2012||05h 41m 20s||25d 28m 54s||6.8|
|December 23,2012||05h 40m 17s||25d 32m 20s||6.9|
|December 24,2012||05h 39m 14s||25d 35m 43s||6.9|
|December 25,2012||05h 38m 12s||25d 39m 03s||6.9|
|December 26,2012||05h 37m 10s||25d 42m 19s||7.0|
|December 27,2012||05h 36m 09s||25d 45m 33s||7.0|
|December 28,2012||05h 35m 08s||25d 48m 43s||7.0|
|December 29,2012||05h 34m 08s||25d 51m 50s||7.1|
|December 30,2012||05h 33m 08s||25d 54m 53s||7.1|
|December 31,2012||05h 32m 09s||25d 57m 54s||7.1|