The Night Sky August 2019
This time last year I wrote about the Summer Triangle, three bright stars that out-shine our light nights during this month. You can use this triangle to help you find your way around the night sky. The triangle is a large pattern but easy to spot as the three stars are almost the first stars to shine through. If you look south, half-way up the sky (over the top of the quarry from Embsay) you will see the lowest of the three stars, Altair. Now look almost overhead to see Deneb to the left, and Vega to the right, to form our triangle.
Using the triangle.
· Trace a line from Vega to Deneb across the sky and it points to the Andromeda Galaxy. This is the nearest major galaxy to us and on a dark night you can see it with your naked eye.
· Starting at Deneb through Altair towards the horizon, you will find Jupiter and Saturn low in the sky. Both planets and gas giants are visible unaided.
· Starting at Altair and working upwards, you will see a very small triangle with a few stars in-line just ahead of the triangle. Directly above these is the Dumbbell Nebula.
The Dumbbell (M27)
The life-cycle of a star has two routes, depending on how large the star has become. Although when we look at the night sky most pinpoints of light look a similar size, stars can vary incredibly in size.
An average-sized star, like our own sun, will in time burn out its fuel and enlarge to become a Red Giant. It will then form a ‘planetary nebula’. This is its outer envelope being blown away as the core collapses to form a White Dwarf. In effect this is a dead star, where fusion has stopped. When we observe the Dumbbell we are seeing the nebula remnants (nothing to do with planets by the way!)
To see the nebula, you will need to allow your eyes to adapt to the low levels of light, then you will be rewarded with a very unusual sight. Not pinpoints of light, but a glow made from gas that has been expanding from a central star that collapsed to form a White Dwarf. The dwarf star is hardly visible at this distance. However, it was similar to our own sun but now is at the end of its life. The overall view looks like a faint diabolo, bow tie or even an apple core. Another Messier object to tick off your list (see my article May 2019)
The second route of a star’s life-cycle is followed when the size of a star exceeds 25 times the size of our sun. As it uses all of its fuel it transforms into a Red Supergiant then eventually explodes into a Supernova leaving behind a Neutron Star or Black Hole. The ‘left-overs’ from the explosion are called supernova remnants, one of the more famous being the Crab Nebula.
Perseid Meteor Shower (12th/13th August)
The annual Perseid meteor shower, one of the best of the year, coincides with a rather bright moon this year. Therefore, most meteors will be washed out by its brightness, but not all! This shower can have a rate of up to 100 per hour as the Earth passes through the debris of the great comet of 1862 known as Comet 109P/Swift-Tuttle. Looking roughly North East and half way up in the sky you find the ‘radiant’, where they will appear to originate.
If you have enjoyed reading this article, don’t forget you can refer to previous ones on my blog at:
Clear Skies.
Milan Davidovic
Comments