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The M.A.S. Newsletter
Journal of the Mauritius Astronomical Society
December 2000
The sky this month:
On the 20th, those looking for Mars can find it just next to the Moon in the constellation of the Virgo at dawn. The planet is now shining at magnitude 1.5 and should therefore not be difficult to spot in the starry sky.
On the 30th, a crescent Moon is visible just above the planet Venus at sunset. On the nights of the 05th and 06th of January, the Moon passes close to the two gas giants Saturn and Jupiter.
The new millennium starts with a lunar eclipse on the 09th of January. The Moon enters the umbra at 22:41, totality starts at 23:49 and ends at 00:48, and finally the Moon leaves the umbra at 01:56. Given the time at which the event takes place in Mauritius, best visibility is expected as the Moon will be at its highest in the sky.
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News:
Astronomers announced on Friday 01st that they had discovered a Kuiper Belt Object (KBO) that potentially could be larger than Ceres, the biggest asteroid. The object, 2000 WR106, is in an orbit about 43 AU (6.45 billion kilometers) from the Sun, with an apparent magnitude of 20. While the object's size is not yet known, estimates based on its magnitude and estimates of its albedo, or reflectivity, mean the object could be between 530 and 1 210 km in diameter. By comparison, Ceres, the largest asteroid, is 920 km across, while Pluto is 2 375 km in diameter. If 2000 WR106's large size is confirmed, it could reopen questions about Pluto's classification as a planet rather than a KBO, since it could be at little less than twice the size of the largest KBO.NASA's Stardust is on track for a January 15 flyby of Earth. Stardust will swoop to within about 6 000 kilometers of the eastern coast of Africa during the early afternoon local time flyby, a manoeuvre designed to give it a gravity boost that will increase its relative velocity and place it in a wider orbit around the Sun. The flyby is expected to take place with little fanfare, unlike the protests that greeted Cassini when it swung past the Earth in 1999 with its 32-kilogram plutonium fuel source in tow. After the January flyby, the period of time it takes Stardust to orbit the Sun will increase by six months, to 2.5 years. That will place the probe on course to swing past the comet Wild 2 in January 2004 and then back by Earth again two years later. In 2006, Stardust will jettison to Earth samples of dust and volatiles it has gathered during its flight past Wild 2, as well as minute quantities of interstellar dust collected at various other stages of the mission. Following the January flyby, Stardust will then enter a prolonged cruise period, lapping the Sun until its 2004 meeting with Wild 2.
More Saturn Moons Discovered: Astronomers announced last week the discovery of four more moons orbiting Saturn, bringing to 28 the total number of moons orbiting the planet. Like the ones announced in recent months, these moons are believed to be small bodies, perhaps no more than a few kilometers in diameter, in distant orbits. Such moons did not likely form at the same time as Saturn but were captured later by Saturn's gravity, perhaps from the Centaur family of small icy bodies that orbit the Sun between Saturn and Uranus.
Some Astronomical Terms:
Oort cloud: A huge collection of remnant cometary nuclei from the formation of the solar system with a total mass about that of the Earth. This cloud of Sun-orbiting comets extends from perhaps 20 000 to beyond 150 000 AU.
AU (Astronomical Unit): The mean Earth-Sun distance. it is used as a unit of measurement for distances within the solar system. Its value is about 149.6 million kilometres. There are about 63 240 astronomical units in a light year.
Merry Christmas and Happy New Year!
