Rock Collecting

Leon Choin

Have you ever been walking along the road or out on a hiking path and stooped down to pick up a neat looking stone? I seem to do this every time I am out walking. Problem is, I bring these home one at a time and pile them on my dresser until my wife comes along and decides it is time to change the view. Poof, they're gone. No one knows what happened to my neat rocks. Well I have found some rocks that are really worth collecting, and no one is going to be able to hide them on me. They are asteroids.

Asteroids are mostly made of rocky and metallic material left over from when the solar system was formed. They come in all different shapes and sizes, just like my other rocks. The asteroid 1 Ceres was the first one found in 1801 by Giuseppe Piazzi. That is why it has the "1" designation in front of it. Asteroids are also known as "minor planets". Three others where found 2 Pallas, 3 Juno, and 4 Vesta, within a few years after the discovery of Ceres. This month we have the opportunity to see the 1st and 2nd asteroids found, or as I like to say, "add them to my rock collection".

1 Ceres is the largest of these rocks and is about 1000 km in diameter. The next largest are 2 Pallas, 4 Vesta and 10 Hygiea which are between 400 and 525 km in diameter. All other known asteroids are less than 340 km across. Most of the asteroids I have been tracking have a periodic orbit of 3 to 5 years. I think this might be true of most the main belt asteroids. So even if they leave my sight, I can plan on their return.

1 Ceres will be easy to find at 7th magnitude. It will be in Libra, about 1° north of Beta Lib at the beginning of the May. It will then make a slow trek across the constellation heading pretty much due west. 2 Pallas will start the month at 8.2 magnitude about 1-1/2° SW of 3 Com heading due north. It will then over the course of a couple weeks make a slow arc to the east and pass just north of 3 com, fading to 8.9 mag as it heads back out into space.

With both these asteroids you should be able to see movement within an hour's time. The way I do it is either print a finder chart for them just before going out and noting their positions or shooting an image of the star field early in the evening and then again before I go in. When shooting an image I convert to a negative image of each and then print them out on plain paper. This way with a simple straight edge I can note the movement, even in a half-hours time. I then date it, note sky conditions and add it to my log. Voila! Another rock in the bag!

A search for "asteroids" on Google will bring up many web pages on the topic. You can also find out more in the what's up this month sections in Sky and Telescope and Astronomy magazines. For a view of a one hour animated gif that I made on April 4th of the asteroid 532 Herculina check at this link.

Leon Choin