By Prashant Naik
The chart above shows the night sky over Shillong during the month of October 2011 at 8.00 p.m. Shillong being at 25.5o N,latitude we see mostly northern constellations. The E-W line shows the celestial equator and the line cutting it shows the zodiac line or the sun’s apparent path. The capital letters indicate the name of constellations and the other letters indicate the prominent stars. Planet Jupiter is visible most of the night (Planet Uranus, and Neptune would be visible through very powerful telescope only.)
The prominent constellations visible are Aquila,Cygnus,Lyra,(the famous summer triangle)Pegasus, Andromeda.,Aries, Draco, ,Bootes,.Cassiopea,Cepheus,Ursa Major, Ursa Minor, ,Aquarius,Ophiuchus, Pisces,Capricornus, Sagittarius, and Scorpius.
The constellation of the month is Andromeda. This is one of the oldest named constellations and formed part Ptolemy’s catalogue. Mythological legend surrounds the naming of Andromeda and it is one of the best-known groups in the sky, not so much perhaps for the stars it contains, but because it includes M31, a giant spiral galaxy very close to our own. These two are the largest in the Local Group of galaxies which contain about 20 members.The three most prominent stars are laid out along Dec 30-40 and virtually span the constellation. Star â, Mirach, is a mag 2’”02 M0 type with absolute mag 0’”2, lying at a distance of 76 light years. Originally in the constellation of Pegasus, and indeed right on the border, can be found á, Alpheratz, a mag 2’”06, B9 star with absolute mag +0’”1, 90 light years from the Solar System. In the opposite direction towards Perseus, ã, Almaak is a mag 2’”14, K3 type with absolute mag -0’”1 some 120 light years distant. It is actually a multiple star with components of mag 3’”0, 5’”0 and 6’”2.
Heading almost directly north from star ä, the keen observer will see with the naked eye a faint hazy patch lying on a similar declination to Almaak. This is the Great Andromeda Galaxy, M31, which has a total magnitude of 5’”0. The galaxy is about 2’”2 x 106 light years away.