Wednesday, 10 July 2013

Vega, neither Vincent or Vic

At this time of year, if you head outside when the sky finally gets properly dark at about 11pm, and look straight up above your head, you will see one of the most attractive sights in the night sky. A brilliant star, brighter than any other in the vicinity, and most notably of all, a star of a beautiful icy blue colour.

This is the brightest star in the constellation of Lyra, the Lyre. It is called Vega - sadly, pronounced Vee-ga Tarantino fans! - and is the third most brilliant star in the night sky visible from the UK. On the cosmic scale it is one of our nearer neighbours at 25 light years away - say a mere 350,000 years travel at Voyager 1 speeds, and is about 40 times more luminous than our sun.

Its strong blue colour - the only naked eye star in the entire sky to be so hued - is down to the fact that it has a surface temperature of up to 10,000 degrees Celcius, compared with just under 6,000 for our sun. To put it simply, the hotter the star, the whiter or bluer it is, and the cooler it is the redder it gets.

Vega in comparison to the sun, from RJ Hall on wikimedia
Vega is also famous for being one of the first stars suspected of having a genuinely extrasolar planet. In 1983 the IRAS infra-red satellite telescope discovered a huge disc of cool material around the star that was believed to be similar to the primordial dust disc around the sun that the earth and other planets fromed from. However, the existence of a planet orbiting Vega has not yet been definitely confirmed, and around a hot, energetic and shorter lived star like Vega the "Goldilocks Zone" may be thin to non-existent.

Not far away from Vega, but sadly entirely invisible to the naked eye, is one of the mst famous objects in the night sky, the 57th object in Charles Messier's catalogue, The Ring Nebula. In small telescopes, it looks like a tiny celestial polo mint, but NASA photos reveal the true wonder of the object, which perhaps to some of you is best known for adorning one of the scanners on the bridge of the original Starship Enterprise!

The Ring Nebula, NASA image

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