Starry Night This Week

Each week most PBS stations air "Jack Horkheimer: Star Gazer", the world's first and only weekly TV series on naked-eye astronomy. The Starry Night images on this page illustrate the show for the week of Monday June 29, 2009. You can view the complete show script, or watch a RealPlayer video of the show.

Earth At Aphelion On The 4th Of July
And The Reason For The Seasons

Earth's orbit is very nearly -- but not quite -- round, so the difference between perihelion (its closest point to the Sun) and aphelion (its furthest point from the Sun) is small compared to the size of the orbit.

Here's a view of the Earth's tilt on the summer solstice. Summer is when your hemisphere is tilted towards the Sun and receives sunlight more directly. You can see that while it's summer in the northern hemisphere, it's winter in the southern -- and if you're at the south pole, your view of the Sun is blocked completely by your horizons!