I am no expert on the subject matter; but what I do know is that NASA has developed this website to present those NEO's they deem to be a
potential hazard I have no idea what this means.
You are correct here. You are in error in your interpretation of what you found on NASA's site. I'm not wanting to defend them in any way since
I'm pretty sure that they'd hide the truth if they thought it would cause a panic.
The error, by their admission, is significant enough that the asteroids in question could be further away from Earth (not by 5 million miles
though) or they could score a direct hit; they don't know for certain. What they do know is that these NEO's present a greater risk for
collision that other NEO's. And they don't use radar to determine this. They use visual telescopes.
When object are found, they need 3 good coordinates that are far enough apart to determine its' speed and trajectory. If they are only able to get 2
poor coordinates before it excapes their field of view, then they calculate using what they have and calculate their range of error. The .00002 AU
from Earth that you pointed out was on one extreme of their margin for error.
You are correct that when they leave a margin for error, they don't know for certain and they could be on a collision course for Earth.
Also, they do use radar to find the NEOs. I don't remember where, but I read about the use of dopplar radar to find and pinpoint locations and
speeds of asteroids. This is one of the things helping them to find so many NEOs these days, many of which are millions of miles away and not much
bigger than your house.
You mentioned an issue of NASA not providing a size. They do, but in astronomical terms. They give it in form of Absolute Magnitude. The larger the
number of magnitude, the smaller the object is. For instance, a 24 magnitude object is somewhere around 40-80 meters diameter, a 26 magnitude is
about 15-30 meters, a 20 magnitude would be about 250-500 meters. Don't confuse absolute magnitude with apparent magnitude.
I made an error in terminology. When I spoke of how solid an asteroid is, I meant more in regards to its' composition. An asteroid made of solid
nickel would withstand a tremendous amount of heat and pressure(speed) on entry to Earth's atmosphere. However, most asteroids are made up of much
less resiliant and dense materials and therefore disintegrate when they impact with Earth's atmosphere. Most meteor fragments that are found on
Earth are of the more resiliant materials...thus they made it all the way to ground level in one or two or three pieces.
Yes. Using nukes on asteroids larger than 50 meters would probably not be a good idea unless used in specific ways.
With today's ability to locate small NEOs, we will probably be able to predict and watch a few fireballs in the next 20 years. NASA will undoubtedly
find some less than 20 meters on an impact course with Earth.