Welcome to another week of what’s happening in the world of Astronomy

8.30 pm March 28th is Earth Hour this year. This is set aside as a time to turn off your lights for one hour to take part in a global event, which is aimed at drawing attention to the need to address the problem of climate change. But as an astronomer, there is another reason why this project is important. Light pollution is the number one threat to the work we do at Siding Spring and other optical observatories around the world.

Light pollution is the illumination of the night sky caused by artificial light sources on the ground (streetlights, billboards, etc.). Both the light and the loss of contrast make it difficult to find fainter stars and nebulae. The amount of outdoor lighting increases as a result of increasing population. As cities and suburban areas grow, the number of lights at night also increases. Lights, contrast, and glare all impact the number of stars that are visible in a given location. Only the brightest stars are visible when there is a lot of night time lighting.

This light is scattered in the atmosphere by particles and aerosols causing the air above urban areas to glow. The end result is that we are unable to see most of the 2500 stars that would normally be seen under dark skies. Astronomers at Siding Spring Observatory are affected in their research by sky glow as far away as Sydney and suburbs. Reducing sky glow, unlike other forms of pollution, actually saves us money and also helps reduce greenhouse gas emissions as well as ensures we can still can enjoy the night sky.

So, while the lights are out for that hour on March 28th and you have the BBQ fired up there is another IYA project you can have a go at!

You don’t need special equipment and you don’t even need to leave home. Between March 16 and March 28 you can participate in one of the IYA cornerstone projects called the Globe at Night. The project invites people to participate in the annual global sky observation known as GLOBE at Night. GLOBE at Night brings people outside to observe the constellation Orion from 16-28 March 2009. Participants simply choose a clear night on which stars are visible, count how many stars you can see in Orion – in particular in his belt and the sword (or for those of us who know it as the saucepan – in the base and the handle), record the time and place and weather conditions such as partly cloudy, clear etc and let me know your results. I am also putting together a kit for groups to use and send back to Siding Spring as a part of this project. If you would like to participate or request a copy just contact me on the details below.

Orion is almost overhead after sunset and then gradually moves towards the west during the night.