Comet Hyakutake came within 15 million kilometers and in 1983, Comet IRAS-Araki-Alcott came within 4.5 million miles. On a scale model of the solar system, draw a circle 6 inches in radius to represent the orbit of the Earth. Place a point somewhere on this orbit to represent the Earth. Comet Hyakutake would be a spot about (15/93) x 6 = 1 inch from the Earth; IRAS- Araki-Alcott would be a spot about (4.5/93) x 6 = 1/4 inch from the Earth! These are two, previously unknown, comets discovered within about the last 10 years.
IRAS-Araki-Alcott was discovered only a week or so before it made its closest approach to Earth. Kind of gives you an insecure feeling inside doesn't it? Care to speculate on the odds that in the next 40 years an even closer comet will be detected? Here is a list of NEO asteroids which are predicted to come within a few million miles.
The above diagram is from the IAU Minor Planets Center and is updated daily. Their caption reads as follows:
The orbits of the major planets are shown in light blue: the current location of the major planets is indicated by large colored dots. The locations of the minor planets, including numbered and multiple-apparition/long-arc unnumbered objects, are indicated by green circles. Objects with perihelia within 1.3 AU are shown by red circles. Objects observed at more than one opposition are indicated by filled circles, objects seen at only one opposition are indicated by outline circles. The two "clouds" of objects 60° ahead and behind Jupiter (and at or near Jupiter's distance from the sun) are the Jupiter Trojans, here colored deep blue. Numbered periodic comets are shown as filled light-blue squares. Other comets are shown as outline light-blue squares.
Copyright 1997 Dr. Sten Odenwald
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