They don’t go away. They remind us not to take them for granted…to think of them.
No, not your grandparents, asteroids! Well, comets too but comets tend not to be stealthy like asteroids. Comets usually give us their calling card way before getting close to Earth, so we’ll know far in advance how desperate things might become. Will it just be a glorious show, or do we need to…yeah, I don’t want to think about that.
Asteroids have a habit of sneak attack. Just when you think all is well with the universe, whoosh – crackle – kaboom, a small one makes us all jump. Last time we jumped was February 2013 and it wasn’t even an asteroid, it was a big meteoroid. What’s the difference? It’s not well defined, but asteroids are much larger. Meteoroids are usually dust grain to pebble size. Large ones, as big as a house, will burn up with a long, bright tail, smoke, and even explode high in our atmosphere, providing an impressive display. Big ones can cause significant damage if one gets close enough to the ground before exploding. The 1908 Tunguska event is thought to be due to a large meteoroid. It exploded about 3 miles above ground, but the compression shock of its explosion flattened over 800 square miles of forest!
Asteroids can be the size of a stadium to hundreds of miles in diameter. Large or small, an asteroid hit is big trouble. A small asteroid impact will severely affect large regions. A large impact can be catastrophic to the planet. Remember that 2017 interloper named Oumuamua? It gave us a scare, as it just zipped in and almost got out of the solar system before detection. At 2000 feet long and 400 feet wide, If Oumuamua had hit us and wiped out a big city, it would have changed us instantly. It would have been a mess.
What can we do?
Be vigilant. Get the earliest warning possible and then take steps to avoid a hit.
Fortunately, many governments and private groups are keeping eyes to the skies, searching for, finding, and monitoring Near Earth Objects (NEOs). The current objective is to find and monitor 90% of NEOs 140 meters in diameter or larger and this close to completion. Once a NEO is found its orbit is determined and will be monitored if it has potential to impact Earth.
Well, we cannot dodge so we need to make the asteroid miss Earth by affecting its trajectory. How do you move a chunk of rock as big as a stadium? We need to know a few things. Is it solid or a collection of rubble? What’s its mass? What are its dimensions? Is it spinning or tumbling?
More on this next week.
What’s in the Sky?
June 11; 45 minutes after sunset; west-northwest: Low in the sky a thin crescent Moon sits below to the right of brilliant Venus.