Comet of the Week: ISON C/2012 S1

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Special Topic: Close Asteroidal Encounters

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Comet of the Week: 29P/Schwassmann-Wachmann 1 1927j

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Special Topic: Comets and Meteor Showers

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JULY 19, 2009: An unknown object, most likely an asteroid a few hundred meters across, impacts Jupiter, leaving a black “scar” in Jupiter’s atmosphere that persists for the next one to two weeks; the “scar” was first noticed by amateur astronomer Anthony Wesley in New South Wales. The “scar” was reminiscent of those produced by …

Perihelion: 1997 April 1.14, q = 0.914 AU  This week’s “Special Topics” presentation discusses, among other things, how the practice of discovering comets has changed over the years. Up until a couple of decades ago a rather large percentage of the known comets were discovered by amateur astronomers regularly scanning the skies with relatively small …

Up until a few centuries ago, all the comets that were seen by human beings were “discovered” via the unaided eye. It is unlikely that there were ever any search efforts for these objects, rather, when they appeared they essentially revealed themselves to the people who were alive at that time. Probably the closest thing …

JULY 12, 2001: American astronomer Gary Melnick and his colleagues publish their discovery of water vapor around the old, evolved star CW Leonis, suggesting the presence of exocomets around that star. The subject of exocomets, including the importance of this discovery, is discussed in a previous “Special Topics” presentation.  JULY 12, 2126: Comet 109P/Swift-Tuttle, the …

Perihelion: 1994 April 18.57, q = 5.380 AU  What could perhaps be considered the most successful search program for comets and near-Earth asteroids during the photographic era, i.e., before the advent of CCD-based comprehensive survey programs in the late 1990s, was conducted by renowned planetary geologist Eugene Shoemaker from 1982 to 1994. Usually once a …

The discovery of the planet Uranus by British astronomer William Herschel in 1781 essentially doubled the size of the then-known solar system. During the years after Uranus’ discovery astronomers began to notice small discrepancies in its orbital motion, and at least two individuals – a young British astronomer named John Adams, and a French mathematician, …