Astronomy for RVers
By Chris Fellows, Serenity Mobile Observatory
During the formation of our solar system about 4.5 billion years ago there was a lot going on. A huge cloud of gas and dust collapsed and 99.8 percent of it fell into what is now our sun. The last 0.2 percent was in a chaotic maelstrom spiraling around the newly formed star, bumping into one another and forming the planets, moons, comets and asteroids that we are left with today. I have talked about all these other bodies in previous articles but realized that I somehow left the asteroids out of those descriptions. Since one of those bad boys is the most likely thing to kill us, maybe I should devote a little time to the subject.
Asteroids are mostly rock and metal chunks of debris scattered all over our solar system. The vast majority are in a region called the asteroid belt between Mars and Jupiter, but there are several other places in the solar system they can be found. For example there is a sub-class of these objects called Trojan asteroids that co-orbit the Sun with Jupiter and are in gravitationally stable points between the two, called Lagrange points. It has been estimated that there are as many Trojans as there are asteroids in the asteroid belt.
Asteroids, at least the ones that are big enough for us to track, are mostly in well-known, stable orbits that don’t pose any real threat to Earth. But the solar system is a busy place and objects gravitationally interact all the time. This can cause orbits to change unpredictably and throw an asteroid out of its heretofore stable orbit into one that will cross Earth’s path. We then rename these objects near-Earth objects (NEOs) or near-Earth asteroids (NEAs). So we should be watching them very carefully because a mile-wide rock traveling at orbital speeds hitting your neighborhood could ruin your day.
Lucky for us, someone was smart enough to set aside some of our tax dollars to fund NASA and other organizations to track the really big ones. The Planetary Defense Coordination Office (what a cool place to work!) tracks about 15,000 near-Earth objects (NEO) today and adds about 30 new NEOs per week to that tally. They calculate the orbits of each one and classify the objects into threat levels to make plans in case one of them is headed for us. These guys are the real Avengers who protect the planet from galactic danger.
Let’s take a look at some of the more notable asteroids that NASA has studied. First on my list is 16 Psyche. Named after the nymph Psyche, who married Cupid but was put to death by Venus. One of the most intriguing targets in the main asteroid belt, 16 Psyche is a giant ball of metal. Its average diameter is about 130 miles (210 kilometers). Scientists think the M-type (metallic) asteroid 16 Psyche is comprised mostly of metallic iron and nickel similar to Earth’s core. Scientists wonder whether Psyche could be an exposed core of an early planet, maybe as large as Mars that lost its rocky outer layers due to a number of violent collisions billions of years ago.
Our next target is 433 Eros. In a break with tradition at the time, the asteroid was given a male name: Eros, son of Mercury and Venus and god of love in Greek mythology. Eros is a potato-shaped rock of about 5 miles in length and doesn’t cross Earth’s orbit. It is notable because it has the distinction of several firsts: It was the first NEO discovered way back in 1898 by Gustav Witt, and it was the first asteroid ever orbited by a spacecraft. The NEAR spacecraft first flew by Eros on Dec. 23, 1998, at a distance of about 2,400 miles.
The picture of Eros (above right), the first of an asteroid taken from an orbiting spacecraft, is a mosaic of four images obtained by NASA’s NEAR mission immediately after the spacecraft’s insertion into orbit. It was the first asteroid humanity ever landed on, on Feb. 12, 2001. Eros was observed with ground-based telescopes for a century before our spacecraft gave us a closeup look. It was the subject of a worldwide observation campaign during its close approach to Earth in 1975, when it was only 14 million miles (22 million kilometers) away.
There are many more of these fascinating objects to learn about and you should check out the science on NASA’s Solar System Exploration website. You can literally spend days learning about our local system.
I hope you enjoyed this look at the rocks flying over our heads, and if you have a telescope you should try to spot one of them. They are very challenging targets.
Till next time!
Chris Fellows, Serenity Mobile Observatory
Find Chris on Facebook (or, if you’re lucky, at your campground). (Editor: Check out his amazing photos on his Facebook page!)