The M.A.S. Newsletter
Journal of the Mauritius Astronomical Society
April 98
Meeting:
The next meeting will be held at midnight on Saturday 2nd of May 1998 next to the church of Cap Malheureux.
ACTIVITY:
Observation of the h Aquarids meteor
shower. Observations will be carried out till early morning on Sunday. Those members
willing to share their car are requested to contact the Secretary (Tel: 686 43 96) to
inform him of the number of places that can be made available. You are advised to bring
warm clothes and some warm food & drink.
Shooting stars:
Since the birth of the
planets, there has been a continuous bombardment of cosmic debris onto them. Today, as
these debris zip through our atmosphere, they give rise to what we call shooting stars:
the debris is vapourised by frictional heating with the air producing a bright tail.
Meteor Showers:
Meteor showers occur when the
Earth encounters a shoal of these debris. This may happen when the Earth crosses the orbit
of a comet. Then the gravitational pull of the Earth causes a large number of these debris
to rain through our atmosphere.
Eta Aquarids meteor shower:
This shower occurs as the
Earth crosses the path of Halley's comet. During the year , the Earth encounters the
debris of Halley's comet twice. The second crossing occurs in October, peaking on the
21st. That meteor shower is called the Orionids. The name given to the different
meteor showers depends on the location in the sky of the radiant. The radiant is
the point on the celestial sphere from which the trails of the meteors of a particular
shower appear to radiate. Thus all the meteors of the h Aquarids shower
appear to come from a point next to the star h Aquarii in the
constellation of Aquarius. For the h Aquarids shower, the maximum is predicted to
occur on the 6th of April.
Scorpius:
The Scorpion is among those
listed by Ptolemy, and one of the few which give a vague impression of the creature it is
meant to represent. Its brightest star, the red supergiant Antares, is 700 times the
diameter of the Sun, with a luminosity of 10,000 times the Sun. Close to Antares is the
globular cluster M4 visible through binoculars. In the claws of Scorpius, there is a
double star b Scorpii, the separation between the
constituents of which is 13.6" . The tail of Scorpius is crowded with interesting
objects such as open clusters, nebulae... This region of the sky is the richest in such
objects since in this direction lies the centre of the Milky Way galaxy.
Birth of X-Ray Astronomy:
On 18th June 1962, a small
Aerobee rocket blasted off from New Mexico. An unusual payload of Geiger counters was
carried to an altitude of 225 km, well above the atmosphere so as to detect X-Rays from
the Moon. This first successful 'X-Ray telescope" did not see the Moon, but rather a
brilliant source of X-Ray in the constellation of Scorpius. This X-Ray source became known
as Scorpius X-1, and is the most powerful X-Ray source in the sky. Scorpius X-1 is a close
binary which contains a neutron star in rapid rotation.
Ophiucus:
To the north of Scorpius lies
the constellation of Ophiucus (Serpent Holder). Ophiucus commemorates the healer
Aesculapius who became so skilled in medicine that he could restore the dead to life. To
avoid depopulation of the underworld, Jupiter disposed of him with a thunderbolt, but
relented sufficiently to place him in the sky. Though Ophiucus is not a zodiacal
constellation, the ecliptic crosses it. Thus, due to the precession of the Earth's
rotation axis, Ophiucus is now the 13th constellation of the zodiac.
Planetary systems found?:
The HST has recently observed
stars accompanied by non-uniform dust discs. Astronomers presume that the 'holes' in the
accretion discs may be due to already formed planets. These observations may have other
explanations though...
Serge Florens, Secretary