Sky lights

With nothing but cloud and rain for the past week or two, I've not had much chance to see anything in the sky. Last night I just about caught the Moon through a very small gap in the clouds but didn't stand a chance of seeing the conjunction of Saturn and Venus. So I turned to the blogosphere and it got me thinking about faint glows in the sky.

On Friday Tom showed a great image of noctilucent clouds which I now have as my desktop wallpaper. Noctilucent clouds are sometimes visible at night during the summer months between latitudes of 50-70 degrees (north or south). They appear to be very high altitude clouds of water vapour that are so high (about 85km) that they are illuminated by the Sun even though it is below the horizon as seen from the ground. They are pretty faint and are not really that well understood.

Another glow that affects astronomers is the zodiacal light. This light is brighter nearer the Sun and seems to follow the ecliptic - the plane of our Solar System. It is thought to be caused by interplanetary dust grains reflecting light from the Sun and the practical upshot is that it sets a limit to the sky brightness. Andrew Jaffe reports that a certain famous postgraduate student - Brian May - recently gave a talk on zodiacal light at Imperial. As is customary for astronomy talks, they all went out for a meal afterwards however it sounds much more rock and roll than you would usually expect.

Posted in astro blog by Stuart on Monday 02nd Jul 2007 (13:35 BST) | Permalink
[an error occurred while processing this directive]
[an error occurred while processing this directive]