Eric Schreur is the planetarium coordinator at the Kalamazoo Valley Museum. He says large space rocks fly by – and occasionally hit – the earth all the time, although the one that blew up in Russia February 15th was unusually large. Five days later, a bright meteor burned up over Florida. Schreur says the Russian meteorite was an event that occurs about once every hundred years. A somewhat larger object flattened forests in Siberia in 1908. Russia is a very large country and you might think that’s the reason it was struck twice in a little over a century. But Schreur says it’s all subject to chance. As he puts it, “You might think of it as two lottery tickets paying off”.
Much, much larger objects have struck our planet in the past. A small asteroid the size of a Boeing 747 jetliner gouged a large crater in the Arizona desert about 50,000 years ago. A collision with huge chunk of rock at least a kilometer in diameter may have killed off the dinosaurs over 200 million years ago. Schreur says the Russian meteorite last month was probably only a third as large as the Arizona object. He says meteors and meteorites (the ones that fall to the ground) get their energy more from speed than mass. The Russian object was traveling about 40,000 miles per hour. It got so bright that it rivaled the sun before exploding into pieces, some of which fell into a lake.
That event prompted renewed calls for a system to track celestial objects that might pose a threat to our planet. Schreur says astronomers have already found about a thousand “near-earth” asteroids a 1,000 km in size or larger. And they discover about a thousand smaller objects every year. One of the latter flew by the earth last month on a path that brought it closer than the geo-synchronous communication satellites orbiting above. Schreur says it was about twice as large as the meteorite over Russia.
Schreur says proposals to prevent large objects from hitting the earth are all in the “blue sky” department. They range from attaching rockets to nudge them into different orbits to painting them a darker color to accomplish the same thing using solar energy. Schreur says, Hollywood versions like the movie Armageddon aside, any attempt to alter an asteroid’s course would have to start long before it would otherwise crash to earth.
Space rocks weren’t the only astronomical events in the news during the last month. Schreur says people in southwestern Michigan may have a chance to see Comet PANSTARRS this month. He says it was discovered during the search for near-earth asteroids using a mountain-top telescope in Hawaii. It has been gradually getting brighter, but not as bright is originally thought. Schreur says it is now about as bright as the stars in the Big Dipper. He says it be visible low in the evening sky, especially with binoculars, beginning in the second week of March. It will be visible near the crescent moon on the 12th. But Schreur says comets are like cats: they do what they damn well please.
The other big announcement from astronomers recently was the discovery of the smallest planet yet found orbiting another star. The “exoplanet” Kepler 37b is only slightly larger than the earth’s moon. Schreur says its discovery shows that space telescopes like the one used to find Kepler 37b are becoming increasingly sensitive. That’s significant because it increases the chance of finding an earth-like planet around another star that could support life.
Heavenly objects get their official names from the International Astronomical Union. It usually draws on classical mythology and the history of science to name new planets and moons. But sometimes a sense of humor comes into play. After two tiny new moons were found circling the now-demoted Pluto, a poll was conducted to name the objects. One of the winners was Cerberus, a mythological no-brainer. But the other suggested name – Vulcan – was inspired by the name of Mr. Spock’s fictional home world in the Star Trek television series.