Slipping towards Winter (October)

Slipping Towards Winter

by Paul Downing

WE
are now at the time of year when the summer constellations and the summer Milky
Way, which we learned about last time, start to slide into the western horizon. But some reminders of summer remain. Look directly overhead at 10pm at the beginning of
October and you will see what looks like a large cross. The bright star at the head of the cross is
called Deneb, in the constellation of Cygnus (The
Swan) and if you use your imagination you will see that the arms of the cross
are the wings of the swan and that the swan seems to be flying along the Milky
Way. Go from Deneb

a little towards the west and you will see another bright star, which is called
Vega. Together with another bright
nearby star, Altair in the constellation of Aquila, the Eagle, they form
a triangle which is called the "Summer Triangle". See if you can work out the triangle from the
star chart this month. An interesting
fact is that Vega and Altair are among the brightest
stars in the sky primarily because they are quite close to us in astronomical
terms (only 25 light years away). Deneb however is very much further away (2,600 light years),
but because it is what is called a "supergiant"

star it appears equally bright to us here on Earth. In fact, Deneb
shines with the brightness of 160,000 of our suns.

This article was printed in October 2006

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