Meteor shower tonight
As night sets in this evening, earth silently plunges through the orbit of comet Swift-Tuttle, encountering debris left over by the comet each time it approaches the sun, every 130 years. The debris rams into the upper atmosphere at speeds of 60...
As night sets in this evening, earth silently plunges through the orbit of comet Swift-Tuttle, encountering debris left over by the comet each time it approaches the sun, every 130 years.
The debris rams into the upper atmosphere at speeds of 60 kilometres per second causing the air to ionise and shed bright streaks of light as the grain-sized particles vaporise. This is what we see as meteors or shooting stars.
This meteor shower has been observed for a long time and is known as the Perseid Meteor Shower or Dmugh Ta' San Lawrenz according to Maltese folk tradition.
The point in the sky - the radiant where these meteors seem to originate - lies in the constellation of Perseus and, hence, the name of the meteor shower, the Perseids.
This year the first quarter moon sets in late evening leaving a dark sky for prime meteor watching hours from midnight till the first glimmer of dawn. Predictions cannot be accurate but the normal rate of the meteors during these hours is 60 per hour.
Watching the meteors does not require any equipment, only dark skies. Before midnight, when the radiant is still low in the northeast, the meteors enter the upper atmosphere at a low angle and few are visible. As night advances, the radiant rises higher in the sky and meteors arrive nearly straight down so viewers will be able to see a larger number.
The Astronomical Society is inviting those interested to join its members and observe this meteor shower from L-Ahrax tal- Mellieha, next to the chapel from 10 p.m. onwards.
A computer presentation describing the meteor shower and the folklore associated with it will be shown on site every hour. Telescopes will be set up by society members for use by the public.
Various objects can be viewed such as nebulae, star clusters and the planet Mars which is fast nearing opposition - when the sun, earth and Mars would be in line. This will happen on November 7 but the closest approach to our planet will be on October 30 when, using a telescope with 80 times magnification, Mars will appear to the unaided eye as big as a full moon.
Two years ago, when Mars was also at opposition, it was closer to earth (the closest in 60,000 years) but was also lower in the sky, causing slight image deterioration and because of a thicker layer of air its light had to traverse.
Mr Grech is PRO, Astronomical Society of Malta.
www.maltastro.org