By Prashant Naik
The chart above shows the night sky over Shillong for July 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. Planets Jupiter and Saturn will rise at the east at this time and visible throughout night.
The prominent constellations visible are, Leo Virgo,Libra, Bootes, Hercules,Cygnus ,Lyra ,Aquila(famous summer triangle), Ursa major, Ursa minor, Sagittarius , Corvus, and Ophiuchus.
The constellation of the month is URSA Major or The Great bear or Saptharshi.This is possibly the most famous of all the constellations because its seven main stars are very prominent and easily visible from the northern hemisphere.
These seven stars, known as ‘The Plough’ or ‘ The Big Dipper’’, only form a small part of the whole constellation. It has a highly irregular outline and prominent stars are spread across a large area.
Taking the stars in sequence, and moving in increasing RA: – Dubhe, is a mag 1.81, KO close double with component mags of 1.88 and 4.82 and 107 light years away; star Merak, is a mag 2.37, A1 type with absolute mag 0.5 at a distance of 78 light years: Phad, is an AO type of mag 2.44 (absolute mag 0.2) 90 light years, Megrez, is a comparatively faint member at mag 3.3 Alioth, is the brightest member of the seven at mag 1.79 with an AO spectrum, absolute mag of 0.2 and it lies at a distance of 68 light years, star, Mizar, is an A2 mag, 2.06 double with component mags of 2.3 and 4.0 and the former is itself a double with component mags of 2.3 and 4.0 and the former is itself a double – the first spectroscopic binary to be discovered : and finally, ç, Alkaid, at the comparatively remote distance of 210 light years, is a B3 type of mag 1.87 (absolute mag – 2.1)
Four interesting doubles are located in the constellation : star è is actually a double with mag 3.19 and 14 : star é has mag 3.12 and 10.8 components : star ÷ has component mags of 4.0 and 4.0 and 4.2; and star o, Muscida, has components of mag 3.57 and 15. There are six Messier objects in the constellation (M81, M82, M97, M101, M109). M97 is themous planetary Owl Nebula, looking like a staring owl, with the remainder being galaxies in their own right.
Full moon will be on July 5 and new moon on 20.The special event during the month is a penumbral lunar eclipse on July 5 which is not visible over India.