ASTRONOMY
Night sky in September

The clear night skies of this month offer the sky-watchers the planets, stars constellations and other cosmic wonders in all their beauty and splendour for viewing and wondering, even though the monsoon clouds attempt to hamper good observations. As it darkens, while facing south, one can marvel at the zodiacal constellations of Libra (scales), Scorpius (Scorpion), Sagittarius (archer), Capricornus (sea goat), Aquarius (water bearer) and Pisces (fishes), which are stretching across the sky from west to east. Later in the night, Aries (ram), Taurus (bull), Gemini (twins), Cancer (crab) and Leo (lion) are seen climbing the eastern sky till dawn. Other constellations are also studding the entire sky throughout the night.

The summer constellations of Aquila (eagle) and Cyguns (Swan) are soaring dominatingly overhead in the sky. The parallelogram of Lyra (harp) and the keystone-pattern of Hercules (strong man) are hanging conspicuously in the western sky. One of the swift rotating stars, Altair (Shravana) indicates the neck of eagle. It is about 17 light-year away. At the top of so-called Northern Cross, Deneb is a prominent super-giant star in swan, lying some 1800 light-years away. The glistening star Vega (Avjijit) in harp is around 26 light-years away. These three stars draw the famed Summer Triangle in the sky.

The board Ophiuchus (serpent bearer), the kite-shaped Bootes (herdsman) with its sparkling star Arcturus (Swati) and the semi-circle of Corona Borealis (northern crown) are slipping out of sight from the western sky. The awe-inspiring Andromeda (princess), the great square of Pegasus (winged horse), Perseus (hero) and tiny Delphinus (dolphin) and Triangulum (triangle) are ascending the eastern sky. The resplendent stars Capella in Auriga (charioteer), Fomalhaut in Piscis Austrinus (southern fish) and the wonderful variable star Mira, in Cetus (whale) are hovering above the eastern horizon. Cor Caroli in canes Venatici (hunting dogs) is glinting near the western horizon.

The circumpolar constellations of Ursa Major (great bear), Draco (dragon), Cepheus (king) and Cassiopeia (queen) are circling Polaris (Pole Star or Dhruba Tara) in Ursa Minor (little bear). Polaris is some 680 light-year away. The shimmering veil of our galaxy the Milky way arches gracefully from northern to southern horizon passing through the constellations of Auriga, Cassiopeia, Cygnus, Aquila and Sagittarius.

The elusive planet Mercury makes its hasty twinkling appearance low in the west after sundown. It is fleeting in the constellation Virgo (maiden). The romantic planet Venus is dazzling in the eastern sky before sunrise, as it speeds across the constellations Cancer and Leo. The red planet Mars is glowing fiery orange in the southern sky after nightfall. It is traversing through the rich star fields in the constellationSagittarius. The mighty gaseous plant Jupiter is visible brightly in the east within a couple of hours after midnight. It is located in constellation of Gemini. The mysterious ringed-planet Saturn is ascending the eastern sky around midnight. It outshines the glittering star Aldebaran (Rohini) and the Star Cluster Hyades in the constellation of Taurus. The softly gleaming planets Uranus and Neptune are residing tin the constellation Capricornus. Planethunters can watch them well during evening in southern sky. The tiny and most distant planet Pluto can be spotted with good telescopes after dark in the southwestern sky in Ophiuchus.

The Asteroids 1Ceres and 10Hygiea are scurrying in Sagittarius and Aquarius. Asteriod 4Vesta is dashing through Taurus. Astronomers have recently located near Pluto the largest asteroid designated 2001 KX76. It surpasses even the biggest Asteroid 1Ceres in size, which was discovered by Piazzi in 1801. Relatively weak Meteor Showers Piscids, Taurids and Delta-Aurigids are active from constellations of Pisces, Taurus and Auriga this month. Periodic Comets 19P/Borrely and P/2001 Q2 (Petriew) are gliding in Gemin/Cancer region of the sky. Another Comet C/WM1 (Linear) is speeding through the area of Auriga, Perseus and Camelopardalis (giraffe). The comets-watchers can track them with good binoculars before daybreak.

An unmanned probe called Genesis meaning the origin or beginning has been launched atop Delta2 Rocket to capture about 10 to 20 micrograms of the solar wind, the charged particles that stream away from our Sun and bring them back to Earth to find out more about composition of our Sun and the birth and evolution of our Solar System. The solar samples would provide invaluable information about the solar nebula, the great cloud of gas and dust that gave rise to the Sun, planets, moons, asteroids and comets. After about a three-month journey, Genesis will reach and park at a point sunward to Earth called the Lagrange Point lying some 1.5 million kilometres away, where the gravitational pulls of the Earth and the Sun are balanced. There it will unfold its bicycle tyre-sized arrays made of diamond, gold, silicome and sapphire and start collecting solar particles. On-board instruments will also record other details about the speed, density and temperature of these tiny flecks. Genesis will then return with its cargo to Earth in September 2004. The capsule containing the samples will parachute down through the atmosphere, where it will be grabbed in mid-air by a helicopter. This special retrieval manoeuvre will help to prevent the samples being damaged by the impact when they hit the ground. Genesis will be the first spacecraft to bring back extraterrestrial materials to Earth since the Apollo astonauts brought back Moon rocks. The mission cost amounts to some US$ 209 million. Genesis is a part of solar problem from NASA and the European Space Agency that studies the Sun from outside the earth. Other Solar Missions like ACE, SOHO, TRACE, Ylysses, Wind and Yohkoh, which are also analysing solar winds, emissions and magnetic fields in great details, are making unprecedented contributions for better understanding of our Sun.

Astronomers have discovered the evidence of a second Jupiter-class planet with nearly circular orbit around out Sun-like yellow star 47 Ursae Majoris lying around 50 light-years away and circa seven billion years old in the constellation of great bear, raising hopes of discovering Solar Systems with planets suitable for life like our own. They had discovered an extra-solar sister planet around this star earlier. So far, seventy exo-planets with eccentric orbits around their parent stars have been discovered outside our own Solar System. It is assumed that these bizarre Solar Systems are inhositable to the forms of life, as we know. Jupiter may have played a key role in development of life on Earth by diverting with its strong gravitational field asteroids and comets like Shoemaker-Levy 9 with potential extinction-level impacts to our planet.

Our Sun reaches Autumnal Equinox on 22 September marking the start of Autumn in the Northern and Spring in the Southern Hemisphere. On this day, the duration of day and night is theoretically equal. The full Moon coincides with apogee on 02 September. It reaches the point in Moon’s elliptical orbit around Earth that lies farthest from us. The new Moon is on 17 September. The accompanying star-chart approximately portrays the night sky in the Northern Hemisphere at about 20 hours local time in mid-September 2001.