Nebulas, because nebulas contain the gas needed to form a star and comets/planets/ asteroids are rocks not gas
5. 3,300 roughly. That should be right around there.
It is allotroph of carbon so it shows metal properties
They are slowed down.
even air is a medium and will slow down waves (slightly) compared to a vacuum/ space
if the wave hits the medium at an angle it can be 'bent' (refracted) like light through a glass prism