A near earth object is an object that has the possibility of hitting earth. They are in a categoriy of objects in our solay system called minor planets.
There are 596595 minor planets known to exist according to the Minor Planet Center. http://www.minorplanetcenter.net/ a Smithsonian Project Funded by a grant from NASA. It is estimated that there are between 10,000 and 100,00 still undiscovered asteroids. They are in our solar system for the most part, blissfully circling the sun as are we and minding their own business.
But many are very close to us and are smaller even than the minor planets that we have in our sights so far. Even conservative estimates would suggest that for every asteroid on a dangerous Earth-Approaching orbit there are hundreds more which have yet to be discovered.
There are also some which because of their size do not get tracked or seen right away, that arrive here on earth. Two or more tons of rocky material rain down upon the Earth daily. So what should be our threshold for concern in these matters?
At this writing I have broken it down to three categories of danger. I hope to refine this list over time.They are 1. Potential Extinction, 2. Major weather changes and massive destruction, 3. Destroying your house. Let’s take these one by one according to size.
1. Potential Extinction; 1100 NEO’s are estimated to exist, larger than1km.These would be considered, ending life as we know it sized asteroids. Out of that number, it is estimated that one might hit the earth every 500,000 years. Remember the dinosaurs? Even though it is not likely soon, it is worth keeping an eye on. Don’t forget that there still may be thousands more of these we do not know about. NASA’s current goal is to discover at least 90% of all NEOs whose diameters are larger than 1 kilometer by 2020.
2. Climate changes and devastation; So what about smaller objects? An object 50 meters in diameter is deemed significant enough to worry about according to the NASA Study to Determine the Feasibility of Extending the Search for Near-Earth Objects to Smaller Limiting Diameters, National Aeronautics and Space Administration, Report of the Near-Earth Object Science Definition Team, August 22, 2003. Prepared at the Request of National Aeronautics and Space Administration Office of Space Science Solar System.
Wow! How bout that HUH? In this study they say, ”We find that damage from smaller land impacts below the threshold for global climatic effects is peaked at sizes on the scale of the Tunguska air blast event of 1908 (50-100 m diameter). According to the Planetary Society web page article http://planetary.org/about/press/releases/2008/0626_Target_Earth_How_Prepared_Are_We.html
It exploded over Siberia – this object from space – and leveled 2,000 square kilometers of forest, flattening pine trees like matchsticks.
Another asteroid about that size left a crater a mile wide and 200 meters deep in Arizona about 50,000 years ago. Now I don’t live in the Siberian wilderness or the expansive desert of Arizona, I live in Los Angeles and I worry more about things like houses, stores, city blocks and such.
3. Asteroids that can take out your house; Another NASA web site. http://www2.jpl.nasa.gov/sl9/back2.html tells us that anything 10 meters or less will mostly burn up according to the density of the matter involved. What a relief right. However when these objects burn up they explode and can drop fragments that are heavy enough take out your garage or worse. These fragments can weigh a ton or more, so 10 meters and larger seems like a good size object to track.
There are currently about 8700 NEO’s being tracked. This site goes on to state that most of these objects are in an orbit between Mars and Jupiter. Today the JPL website lists,1293 known and tracked potentially hazardous NEO’s, listed on their Near Object Project page. They range from several meters long and wide on up. You can see the orbits of each of these at http://neo.jpl.nasa.gov/orbits/
Congress mandated in 2005 that NASA discover 90 percent of NEOs whose diameter is 140 meters or greater by 2020, and asked the National Research Council in 2008 to form a committee to determine the optimum approach to doing so. In an interim report released last year, the committee concluded that it was impossible for NASA to meet that goal, since Congress has not appropriated new funds for the survey nor has the administration asked for them.
What’s a mother to do? Telescopes anyone?
Being a regular guy as I am, it seems reasonable to me to assert that since we have the technology available, ie telescopes and video capable of recording events in the night sky, far out into space, and of course the computers to analyze the data, that I am not being too outrageous in expecting that if a trackable two ton chunk of the solar system, that explodes off of a 10 meters diameter or larger NEO, is going to fall within a mile or so of me during the day or night, I ought to be able to know about it. Am I wrong?
There ought to be an app for this right? Call it, NEApp for near earth asteroid position predictor or something. So let’s get on this professional and amateur astronomers. There has got to be a buck in this. Sponsors perhaps. Finding all this suff could be fun
In the coming articles we will discuss more NEO stuff as well as astronomy as a way to do some big brain chill in your spare time.