Monday, 20 July 2015

Astrognome Astronomy The Summer Triangle Part 1

The Summer Triangle Part 1: Vega

If you look directly overhead during summer evenings you will see a bright blue/white star. This is Vega the brightest star in the constellation of Lyra the Lyre or Harp, which according to Greek legend Apollo gave to the great musician Orpheus.

Vega is about 26 light years away, this means that the light entering our eyes this summer left Vega in 1989. Anyone born in 1989 the light from Vega left the star the year you were born!

It is blue/white in colour, this means that Vega is hotter than our Sun. The colours of stars tell astronomers which stars are hot and which are cool. Surprisingly blue/white stars are much hotter than orange/red stars.

Although Lyra is a small constellation there is a lot that can be seen without the help of a telescope.

Just below Vega you will see a small rectangle of stars the bottom right is beta Lyre or to give its proper name Sheliak. This star varies in brightness and is referred to as a variable star.  It is quite easy to watch it change in brightness every 13 days. There are many different kinds of variable stars. Beta however was first identified as variable by the English astronomer John Goodricke in 1784. Goodricke was deaf and unable to speak. He is however one of the fathers of variable star astronomy.  

To the left and slightly above Vega is the star is epsilon, it is marked as e2, this star is in fact double and if you look carefully you will see there are two stars  rather than one.

Vega was once our North Star but because the Earth wobbles very slowly the position of the North Star changes. It takes the Earth 26,000 years to wobble once. Vega will be the North Star again in about 12,000 years!

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