The M.A.S. Newsletter
Journal of the Mauritius Astronomical Society
December 99
The Next Meeting:
...on the night of Monday 13th to Tuesday 14th of December at 01:00 am (Tuesday) next to the chapel at Cap Malheureux for the observation of the Geminids meteor shower.
The sky this month:
On 3rd December, Mercury is at its maximum western elongation. It is then at magnitude -0.5 and visible at dawn in the constellation of Libra. The magnitude of Venus, now in the constellation of Virgo, is declining to reach -4.1 by the end of the year. A fine crescent Moon (13% illuminated) is in conjunction with Venus at dawn on the 4th and with Mercury on the 6th (3% illuminated).
Owners of telescopes with an aperture greater than 10cm wishing to observe the Great Red Spot of Jupiter can obtain a time-table of the spot's visibility for December from the Secretary (sflorens@intnet.mu), 47 Vengta road, Solferino.
A Comet for next year:
The newly discovered comet C/1999 S4 (Linear) is expected to be at its nearest to the Sun in July next year. On the 24th of July it will be at a distance of 55 million kilometres from Earth and will be visible (expected magnitude: less than 4) in the constellation of Leo shortly after sunset in the western sky not far from the brightest planet Venus (mag -4.46).
Replacing HST's faulty Gyros:
Discovery is scheduled for launch on mission STS-103 at 07:37 UT Monday, December 6, nearly two months later than originally planned because of delays incurred by wiring inspections and repairs throughout the shuttle fleet. Discovery will fly a 10 day mission to the Hubble Space Telescope, where four astronauts will perform a series of spacewalks to replace faulty Gyros used by Hubble to point accurately, as well as make other repairs and upgrades to the orbiting observatory. The shuttle can launch as late as December 14, which would imply a landing on December 24, Christmas Eve, although if needed NASA is willing to allow the shuttle to stay in orbit over Christmas. If the shuttle cannot by December 14, the launch would likely be postponed to at least early January, so that the shuttle is not in orbit over new year's day thus not susceptible to any unforeseen Y2K computer problems.
New meteor shower:
A new meteor shower predicted by some astronomers to be visible in early November as a warm up to the Leonids failed to materialize. With only a few meteors noticed by observers, the "surprise" shower, informally dubbed the Linearids, was predicted to be visible around November 11 when the Earth passed very near the orbital path of newly-discovered long period comet C/1999 J3 Linear, just 40 days after the comet was in the same area. This orbital coincidence led some astronomers to predict the possibility of a meteor shower, as dust left behind by the comet in its orbital path streaked through the Earth's atmosphere. This would be visible on Earth as a shower of meteors appearing to radiate from the bowl of the Big Dipper in the constellation Ursa Major. Reports disseminated through the Internet in the days after predicted peak of the Linearids, though, showed no signs of any shower observed by astronomers. Most only reported one or a few meteors coming from Ursa Major per hour.
This was not a surprise for some astronomers. Existing meteor showers, such as Leonids, are associated with short-period comets, rather than the 63,000 year period C/1999 J3 Linear. Short-period comets can build up streams of dust throughout their entire orbital paths, so that the showers can be seen on annual basis.
The next Leonids:
While no major storm was predicted for 1999, and forecasts for 2000 call for only a minor shower, astronomers should keep an eye out for 2001 and 2002. The forecasts by McNaught and Asher predict up to 15,000 meteors per hour in 2001 and 25,000 per hour in 2002 as the Earth passes through newer, denser regions of the dust trail in the orbital path of comet Tempel-Tuttle.
Merry Christmas and Happy New Year!
Serge Florens, Secretary