The eclipse is coming!
March 18, 2015
We’ll be setting up our solar telescope outside the South Downs Centre in Midhurst this Friday morning in the hopes that we’ll be able to watch the solar eclipse. If you’re in the area please come and join us.
But will the weather stay clear? Dark-skies Dan, who’s leading on our bid for the South Downs to become an International Dark Skies Reserve is keeping his fingers crossed.
“Think yourself lucky. Over the billion years of the evolution of our solar system, this Friday will be host to one of those rare cosmological events – an eclipse of the sun.
“But just how rare?
“It just so happens that the sun is 400 times further away than the moon, which is fortunate as the moon is 400 times smaller. When the two cross paths the moon eats out the sun until it completely blocks the light from its surface, what is called a total eclipse. At this point you can see the atmosphere of the sun – the corona – and if your lucky some of the brighter planets that may be nearby. Lucky.
“But the distance between the moon, the Earth and the sun always changes. Over millions of years slight differences in the orbits means that not all eclipses are the same. Sometimes the moon appears smaller as it’s further away from us and doesn’t completely blocking out solar disc, called an annular eclipse. And then – as is the case on Friday – our position on Earth means we just miss out on the ‘path of totality’. Here we will see a partial eclipse where around 85 per cent of the sun will be covered. Still good to see – with appropriate solar glasses – but not quite the awe inspiring diamond ring that we last saw in August 11 1999 – I saw it!
“But as the moon is slowly receding from us at a speed of 4cm a year, in a few aeons the moon will be so far away that it will never cover the disc and we’ll never get totality (unless we travel in spaceships to right point). How lucky is that?
“Well, quite a lot. Even though we’ve catalogued around 1,800 exoplanets, we don’t know how many have got moons. So as we don’t know the sizes, the distance and the orbits we can’t really tell just what the astronomical odds are that we are blessed with such a rare event.”
“So although an eclipse happens on Earth roughly every two years, galactically it could be very rare. And who knows, in a few centuries we could be a exo-tourist destination. Wouldn’t that be a challenge for South Downs tourism!”
Find out more about our bid to make the South Downs an International Dark Skies Reserve and take the Dark Skies pledge.