Bernard Verhoeven, Jr., age 13, of Phoenix, Arizona, for his question:

What is the difference between an asteroid and a satellite ?

Suppose we could capture an asteroid and a satellite and put them on exhibit in a large park. Each would be a chunk of solid rocky material. The asteroid might be smaller, but we couldn’t be sure of that. Without proper name plates, we couldn’t be absolutely sure which was which. In fact, sitting there in the park, neither would be either a satellite or an asteroids

Far whether one of these chunks of matter is an asteroid or a satellite depends upon its orbit in the solar system. And it may be possible for an asteroid to leave its orbit trolley tracks and become a satellite.

The word satellite means an attendant. In star talk we save the word for the smaller planet like bodies that circle the nine known planets. Earth has one satellite, held by the planet’s gravitation and circling at a speed which keeps it at an average distance of 239,000 miles   our own golden moon. Mars has two small satellites, Jupiter has  dozens. All these satellites circle their planets and, along with planets, circle the sun.

The thousands of asteroids travel roughly between the orbits of Mars and Jupiter. Some are larger some smaller than the known satellites, they travel in orbits around the sun as though they were planets. In fact, some people think that the asteroid belt is the fragments of a whole p1anet which once existed between Mars and Jupiter. If such a planet did break apart, its pieces might well continue in its planetary orbit, as the asteroids roughly do.

The orbits of these asteroids sometimes take them far afield into the orbits of neighboring planets, Suppose a fairly fast traveler came within a few thousand miles of the earth, The earth’s gravitation might hold it from escaping, and its own speed might prevent it from falling and keep it circling around us. The asteroid days of this heavenly body would be over – it would now be a satellite our Earth would gain an extra moon though maybe too small for any but the keenest of telescopes to spot.