Asteroid Apophis - existential threat or spectacular sky show?
This blog was posted (slightly edited) as an article in Crux, the Magazine of the Astronomical Society of Victoria, vol.39 no.2 April 2021. Our neighbours the asteroids Asteroids are pretty much everywhere in our solar system. Typically, they have highly elongated orbits, meaning they can cross the orbits of the planets, as the planets have much less eccentric (that is, nearly circular) orbits. There are several classes of asteroid, determined by the amount if time they spend inside or outside Earth's orbit. Atira - spend their entire time inside the Earth's orbit Aten - cross Earth's orbit but spend the majority of time nearer to the Sun Apollo - cross Earth's orbit but spend the majority of time further out than the Sun Amor - spend their entire time outside Earth's orbit Most of the Atira and Amor classes are quite safe, although some of them can approach Earth's orbit closely. However, the Aten and Apollo types don't only approach,