Those of us who live in the Northern hemisphere have probably forgotten the comet because it was only visible to the naked eye of those who lived south of the equator. We are referring to Comet C/2001 Q4 (NEAT) , a rather neat name for a comet. Discovered three years earlier, the comet made its closest approach to Earth in May of 2004 when it came within 0.32 AU from our planet. That’s almost 48 million miles, and although that’s 18 million miles closer than Venus ever comes to us, it’s not very close compared to other comets, as revealed by the following list. In 1999, the small comet, P/SOHO 5, came within only 1.8 million km of us, only 4.7 times as far as the moon!
The more interesting thing about Comet NEAT is that its trajectory is hyperbolic. A hyperbola gives one the false impression that its source must come from outside the solar system. But Comet NEAT comes from the Oort cloud, one of two distinct regions of the solar system that gives birth to comets. Although the spherically shaped Oort Cloud is the source of long-period comets ( more than 200 years), encompassing the solar system between distances of 1000 AU to 100,000 AU, it is not uncommon for a gravitational disturbance to change an Oort-comet’s orbit from an elliptical to a hyperbolic shape. Currently, Comet NEAT is on its way out of our solar system, having crossed the orbit of Neptune in 2014. A NASA JPL applet tracks its location.
Comets are believed to contain the most pristine material left over from the presolar nebula. They provide hints about how complex molecular
species are formed. Thanks to interferometry from the old BIMA array of 9 radio telescopes, methanol (CH3OH), carbon monoxide CO, carbon monosulfide (CS), and methyl cyanide(CH3CN) were identified in Comet NEAT. Other comets include alcohol, cyanide, even amino acids. It has been speculated that they have brought us water along with the organic soup required for the origin of life.