This week Hal illuminates us on some particular particulates.
Our Solar System is mostly empty space. Extending across billions of miles, the Solar System you learned about in school contains eight or nine planets, depending on how old you are, with the Sun in the middle, and lots of empty space between. But as with most things, it’s a little more complicated, and a little more beautiful, than you might think.
Have you ever been driving west in the Spring, not long after sunset, as the sky is darkening, and seen what looks like the glow of a distant city rising from the horizon, when you know there is no city out there? If so, you may have seen a wonderful astronomical phenomenon known as zodiacal light. So just what is it you are seeing? For many years, it was thought that this glowing triangle of light was caused by the Sun illuminating particles in the Earth’s upper atmosphere. But the truth is far more interesting and exciting.
While it is true that the Sun and the planets are by far the biggest things in the Solar System, they are not the only things. You may have heard about the Asteroid belt, a debris field mostly between the orbits of Mars and Jupiter. This area of space contains countless objects left over from the time the planets were forming, ranging in size from tiny particles to planetoids nearly 600 miles across.
While most asteroids are far out in space, as it turns out the inner Solar System is also filled with debris left over from when planets were forming four and half billion years ago. But the debris in the inner Solar System isn’t big rocks, it’s dust. And twice every year, before dawn in the Fall and just after sunset in the Spring, the geometry of the solar system allows the Sun to light up this interplanetary dust cloud brilliantly. So keep your eyes peeled as you look to the west as night begins, and see if you can see one of the Solar System’s dirty little secrets – it’s dusty.
If you’d like to take a closer look at zodiacal light, or any of the other wonderful and amazing things in the sky, please visit KRCC.org or CSASTRO.org for a link to information on our monthly meetings and our free public star parties!
This is Hal Bidlack for the Colorado Springs Astronomical Society, telling you to keep looking up, Southern Colorado!