The 365 Days Of Astronomy, The Daily Podcast Of The International Year Of Astronomy 2009

Things that orbit the Sun and clear their orbits. Dear Cheap Astronomy – What happens when worlds collide? The outcome of a collision between two planets depends on the speed of the collision, the angle of the collision and the relative masses of the two bodies and their composition – think rocky planets versus gas giants for example. A small planet approaching a large planet slowly might get tidally stretched and break up into pieces, but a fast moving one might impact before there’s been time for gravitational stretching to break it up.   Dear Cheap Astronomy – Why is Mars’ sky red? A good place to start is to think about the colours we are familiar with in Earth’s sky. In the middle of the day, the overhead Sun is a bright white disk you can’t look at directly and the rest of the sky is blue. This is because most of the visible light from the Sun passes straight through the atmosphere, which is transparent to those wavelengths, except at the very short end – so rather than passing straight through, photons