Nightskywatching
by
Kamal Lodaya

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Every issue, JM has a map of some stars seen during the month, with a small explanation. Take this map to a place where the sky when you face North is dark and there are no lights in that direction. East is where the Sun rises in the morning.
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The map shows stars seen at 9 pm on June 1st, or at 8 pm on June 15th, or at 7 pm on June 30th. Take a few minutes to let your eyes get adjusted to the darkness. Then you will start seeing stars. Use a small torch (maybe from your phone) covered with red paper to give a soft red light to the map. Red light interferes least with your ability to see things in the dark.
Facing North, you will find the large constellation of Saptarshi with four stars forming a quadrilateral, and then a curving arc of three stars pointing upwards. Following that curve overhead you will find the bright yellowish star (vinmeen) Swati, called Arcturus in English. Follow the curve some more and you come to Chitra, a bright white star in the constellation Kanya or Virgo, the Young Girl. Follow the curve a bit more and you reach the little constellation of Hasta, known as Corvus the Crow in English.
Those seven stars have names: in order, Kratu, Pulaha, Pulasya, Atri, Angira, Vasishtha and Marichi, the seven rishis, in English it is called the Great Bear. (Do bears have tails?) It is one of the best known constellations, you might even find someone who knows it and can show it to you.
If the sky is clear, very close to Vasishtha you will find a faint star, named after his wife Arundhati. This pair of stars is mentioned in the Mahabharata, which was written from about 800 BCE to 400 CE, so around 2000 years ago. Now they could be just in the same line of sight as seen from Earth, but they are reasonably near each other, about half a light year from each other. (Our Sun is 8 light minutes away from us. The two stars are around 80 light years away) It is not known if they are a real couple, that is, whether they are bound to each other by gravity.
More recently it was pointed out to Galileo Galilei in 1617 (which he checked with his telescope) that the star Vasishtha (Mizar in Arabic and English) is itself a pair, in this case the two stars of the pair appear equally bright. Separated by about 4 light days, they actually revolve around each other over thousands of years. 
Each of these stars, Mizar A and Mizar B, are themselves double stars revolving around each other, Mizar A has identical twins, both yellow and 35 times as bright as the Sun, revolving around each other in about a day. The Mizar B pair revolve arond each other in about six months. All this we cannot see. It was inferred from the Doppler shift seen in its spectrum by astronomer Antonia Maury in 1890. She was the first to find such a spectroscopic pair. If you lived on a planet there you would have four suns in the sky. What fun!
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5th June is Full Moon (Jyeshtha Poornima) and 21st June is New Moon. The month of Jyeshtha ends with the amavasya and the month of Ashadha begins. Why are they called Jyeshtha? Check out the July night sky.
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Questions: Please send questions and experiences about your night sky watching to JM.