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Ice and Stone


Comet of the Week: 9P/Tempel 1

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Special Topic: Past Spacecraft Missions

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Special Topic: The Tunguska Event and Other Recent Impacts

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Special Topic: Orbits and Future Returns

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APRIL 26, 1803: A collection of over 3000 meteorites falls and lands near the town of L’Aigle in Normandy, France. Up until then the existence of “stones falling from the sky” had been harshly debated, but the L’Aigle meteorite fall conclusively proved that such events happen, and in effect gave birth to the study of …

Perihelion: 2004 April 17.09, q= 0.168 AU  One of the most legendary comet discoverers of the 20th Century was the Australian amateur astronomer William Bradfield, who resided near Adelaide, South Australia. By trade a rocket propulsion engineer with the Australian government until his retirement in 1986, Bradfield began a systematic visual comet hunting effort at …

Interplanetary space in the vicinity of Earth’s orbit – and, presumably, elsewhere as well – is littered with debris. Dust ejected from comets, bits and pieces of asteroids, rocks from various bodies . . . Meanwhile, Earth during its annual orbits around the sun is constantly sweeping up this debris. From the standpoint of terminology, …

APRIL 20, 1910: Comet 1P/Halley passes through perihelion at a heliocentric distance of 0.587 AU. Halley’s 1910 return, which is described in a previous “Special Topics” presentation, was quite favorable, with a close approach to Earth (0.15 AU) and the exhibiting of the longest cometary tail ever recorded.  APRIL 20, 2025: NASA’s Lucy mission is …

Perihelion: 1957 April 8.03, q= 0.316 AU  There weren’t any bright comets that appeared the year I was born, 1958, but two bright comets appeared the previous year. These two objects were the brightest comets to become easily visible from the northern hemisphere since the return of Comet 1P/Halley in 1910.  The first of the …

Throughout “Ice and Stone 2020” I refer to numerous specific objects, including in all of my “Comet of the Week” presentations as well as in several of my “Special Topics” presentations and in the lists of weekly historical events. It is appropriate, then, to discuss how these various objects are designated and named.  The conventions …