Time – One year before impact
Scientists discovered the asteroid D-1. The asteroid is currently 3.6 AU from the sun as it travels closer to earth. It is moving at a speed of 14 km/s.
Time – Impact
The asteroid will be traveling at 38 km/s. Both the asteroid and earth will be located 1 AU from the sun at this time. The asteroid is predicted to hit the earth at an angle of 79 degrees.
Important things to think about….
1) The earth will move once around the sun in the time it takes the asteroid to move to impact. So, as the asteroid is moving towards the sun…the earth is revolving. After one year, they will be in the same spot.
2) Due to conservation of angular momentum (and Kepler’s second law), the asteroid will gain speed as it approaches impact. All objects in an elliptical orbit move the fastest when they are closest to that which they are orbiting, in this case the sun. They move the slowest when they are farthest from that which they are orbiting. So, the asteroid is gaining speed as it approaches the sun and impact.
The earth moves in an elliptical orbit around the sun. This ellipse is more round than it is flat however. Since the earth’s path is almost circular, we are simplifying the scenario by doing our calculations assuming the earth moves in a circle instead of an ellipse. (The eccentricity of a circle is 0. The eccentricity of the earth is 0.0167.)