Guest Author - Barbara Melville

We See the Universe as it was

Have you ever heard someone say that you’re seeing the past when you look up at the stars? It sounds romantic and perhaps even silly, but it is correct. For example, when an astronomer views the Andromeda galaxy, he/she is seeing how it was 2.5 million years ago. This is because it has taken that long for the light to reach us here, offering a window into the past that no history book ever could.

Visible Meteors are Usually Very Small

Ever seen a “shooting star”? Many of these bright meteors that you see streak across the sky are about the same size as a salt grain. There are even smaller ones, too. Microscopic meteorites, called micrometeorites, fall down on Earth all the time. If you’ve been outside recently, you might even have them on your person.

Objects Orbit Black Holes

Imagine the Sun was massive enough to become a black hole (it isn’t, but let’s pretend for now that it is). Would the Earth go tumbling in, never to be seen again? Actually, it wouldn’t. It would continue to orbit the black hole alongside the other planets. This is because orbit is determined by distance and mass, not size. As it happens, the Sun can’t collapse into a black hole, and has a few billion years of life left.

The Biggest Known Star

The biggest star is VY Canis Majoris, a red hypergiant 5000 light years from the Solar System. It has been estimated at around 2000 times the radius of the Sun, but only around 30 times more massive. Since it’s very difficult to imagine something that size, I’d recommend watching this animation that compares the Solar System planets to the Sun, and then these much bigger stars such as Pollux, Betelgeuse and VY Canis Majoris.

For information on some star myths, read Stars – Common Misconceptions. For those interested in black holes, Black Holes – an Introduction is a short article covering the basics of these fascinating objects.

Sources

Galaxies, Universe (8th edition), published by W.H. Freeman and Company in 2007, authors: Freedman, R. and Kaufmann III, W.

Target Earth: Asteroid and Comet Impactors, Death from the Skies!, published by Viking in 2008, author: Plait, P.

Ten Strange Facts about Astronomy and Space, Astronomy for Dummies, published by Wiley in 2005, author: Maran, S.

What if the Sun became a black hole?, NASA (The Space Place) website, accessed: 25th January 2009, no author specified.

VY Canis Majoris: The Astrophysical Basis of Its Luminosity, published by the University of Minnesota School of Physics and Astronomy in 2006, author: Humphrey, R.M.