AU

Michael A. Seeds defines an astronomical unit (AU) in his book Foundations of Astronomy as "the average distance from Earth to the sun; 1.5 x 10^8 km, or 93 x 10^6 miles." If you divide this distance by the speed of light, you find that it takes approximately eight minutes for light to reach us from the sun.

In the background picture of my blog, I am looking at the sun through my telescope during the last Venus transit of our lifetimes. The next one won't be until 11 Dec 2117! (www.transitofvenus.org) 

I used a filter, of course. Never look directly at the sun. 

Here are some photos from the Venus transit, 06 Jun 2012:

It was very difficult to take a picture of the Venus transit through the telescope, but my boyfriend did it! Can you see that tiny black dot on the sun? That's Venus! The transit of Venus can be used to determine how far away from the sun we are, also known as an AU. (Seeds)

Here are two other safe ways to observe the sun. There are special glasses that are made for looking at the sun, and special instruments that project the sun onto a white surface. The dark dot on this surface is the shadow cast by Venus.

Tomorrow I will show you how to make a pinhole projector to safely observe a solar eclipse and also how to observe sun spots and what they are.