The M.A.S. Newsletter

Journal of the Mauritius Astronomical Society


November 2000


The Next Meeting:

The next meeting, weather permitting, will be due Friday 24th of November at 19:30 at Collège du Saint Esprit, Quatre Bornes for the observation of the planets Saturn and Jupiter close to opposition.


The sky this month:

Opposition for Saturn occurs on the 19th, and for Jupiter on the 28th. Telescope owners can find the great red spot crossing the central meridian of Jupiter (at best on the Earth facing side of the planet) at the date and time shown below.

13th    01:15, 21:06        22nd    03:37, 23:29
15th    02:53, 22:44         25th    01:07, 20:58
18th    00:22, 20:13         27th    02:44, 22:36
20th    02:00, 21:51         30th    00:14, 20:05
02nd    01:52, 21:43


The Leonids:

The meteor shower is back this year with its maximum on the night of the 17th to 18th. The show will start at about 02:00 and the peak of activity is expected after sunrise. The moon, at last quarter, will somewhat spoil the show. Internet sites:

www.estec.esa.nl/spdwww/leonids
www.leonid.arc.nasa.gov/index.html
www.imo.net


News
:

An international team of astronomers announced Wednesday it has discovered four more moons orbiting Saturn, apparently putting the gas giant back on top as the planet with the greatest number of known satellites. The four faint bodies, spotted over the last two months at telescopes scattered across the globe, bring the number of known moons orbiting Saturn to 22. With that, Saturn edges out Uranus, with 21 natural satellites, on the moon front. Estimates of their size -anywhere from 10 to 50 kilometers across - are based on assumptions of their reflectivity. However, astronomers have been able to determine that the irregular moons - meaning they orbit outside the plane of Saturn's equator -are not asteroids, thanks to orbital calculations done by Brian Marsden of the Harvard-Smithsonian Center for Astrophysics. Nor are they likely to be comets. "The probability of that is very small," said Gladman, of the Observatoire de la Côte d'Azur in France. Gladman added that several more months of calculations should allow astronomers to pin down the moons' orbits. The four moons are the only other irregular Saturnian moons found since William Pickering spotted Phoebe in 1898. The moons are believed to orbit Saturn at a distance of anywhere from 10 million to 20 million kilometers. In contrast, Saturn's moon Titan - which will be visited by Cassini's Huygens probe in 2004 - orbits just 1.2 million kilometers from the planet. Unlike Saturn's regular moons, which formed from the accretion disk that once surrounded the planet, the newly discovered satellites were likely captured into orbit after the gas giant formed. As such, the "new" moons are actually quite ancient. Indeed, the icy bodies could very well be primitive remnants of the earliest building blocks of the solar system. For now, the additional moons bear the provisional code names of S/2000 S1, S2, S3 and S4. Following additional observations, the International Astronomical Union (IAU) will certify them as true planetary satellites, and more lyrical names will be given. By astronomical convention, Saturn's moons bear the names of Titans and other figures taken from ancient Greek mythology. Between 1997 and 1999, the same team discovered five more moons orbiting Uranus. While the astronomers caution the new discoveries at Saturn are preliminary, they also said they have discovered other objects that are likely Saturnian moon candidates. Promising a further bounty, the spacecraft Cassini should reveal even more satellites within Saturn's rings after it arrives in orbit around the planet in 2004.


Some Astronomical Terms:

Opposition: The position of an outer planet when it is opposite the Sun in the sky. Then the planet is at its closest approach to the Earth and reaches its highest point in the sky (culminates) at midnight. As the orbits of the planets are elliptical, some oppositions bring the planets closer to Earth than others.

Culmination: The moment when a celestial object reaches its maximum (and also minimum for circumpolar objects) altitude above the horizon as the Earth's rotation takes it across the sky. Circumpolar stars culminate above and below the pole, these events are called upper and lower culmination respectively.


Some Internet Sites:

www.astrosurf.com
www.jpl.nasa.gov
www.club-internet.fr/perso/legault
www.maison-astronomie.com
www.eso.org
www.pds.jpl.nasa.gov/planets
www.ghgcorp.com/akelly
www.astronomynow.com
www.medas.fr
www.fourmilab.ch
www.spaceviews.com
www.heavens-above.com


Serge Florens, Secretary

Back to Archives