THE SUMMER NIGHT SKY
VIEW OF THE SKY LOOKING SOUTH AT 9:00 pm ON 1st JULY
The only bright star in Bootes is Arcturus. It is an orange giant about 23 times the diameter of our sun, that is about 23million kilometres, our sun is 1million. It is about 1000 degrees K cooler than the Sun but because of its size it appears to be about 100 times brighter. It is quite close, being only 35 light years from our sun.
One of the most beautiful objects in the sky is just above our heads at this time of the year in the constellation of Hercules and visible even to the naked eye. This is Messier 13 (M13), a great globular cluster of stars in the constellation of Hercules. M13 is one of the finest star clusters in the northern sky and can actually be glimpsed with the naked eye on a clear night and is easy to find using binoculars. To see M13 in its full glory does of course require a modest telescope but even in a small instrument or binoculars it can still be seen
Just coming into view in the east is Cygnus. This is a beautiful constellation which has a lot of interesting things to see. During late summer and autumn it is almost directly overhead. It forms a distinctive cross shape which does actually look a bit like the Swan it is named after. When viewed through binoculars or a telescope the observer is first amazed by the number of stars in the field of view. This is because Cygnus sits right on the Milky Way and has a background of rich star fields. The bright star Deneb is one of the brightest stars that we can see in our skies it is a bright hot white star, much brighter and hotter than our own sun at 10000° C.
The star at the swan's head end of the centre line of the cross forming Cygnus, furthest from Deneb, is interesting and beautiful to look at in a telescope. It is actually a double star comprised of non identical twins. One star is a bright golden colour while the other is a beautiful ice blue. Because they are so close together the colour difference is very noticeable. The blue star is very hot star and the golden yellow one is a star with a temperature similar to our Sun.