THIS WEEK IN HISTORY
WEEK 35: AUGUST 23-29
AUGUST 23, 1862: The comet now known as Comet 109P/Swift-Tuttle passes through perihelion at a heliocentric distance of 0.963 AU. The comet had been discovered the previous month independently by Lewis Swift and Horace Tuttle, and became a conspicuous naked-eye object. It is the parent comet of the Perseid meteor shower and is a future “Comet of the Week.”
AUGUST 23, 2007: British astronomer Brian May, best known for being guitarist of the rock band Queen, successfully defends his doctoral dissertation on the subject of the motions of dust streams within the zodiacal light. Dust in the solar system is the subject of this week’s “Special Topics” presentation.
AUGUST 24, 2006: On the last day of its General Assembly in Prague, Czech Republic, the members of the International Astronomical Union remaining in attendance vote on a definition of “planet” that excludes Pluto and introduces a new category of solar system object, the “dwarf planet,” into which Pluto and several other worlds, including the main-belt asteroid (1) Ceres, are placed. Pluto is discussed in a previous “Special Topics” presentation, and the Kuiper Belt objects whose discovery precipitated this issue are discussed in next week’s “Special Topics” presentation.
AUGUST 24, 2020: The Amor-type asteroid (85275) 1994 LY will pass 0.115 AU from Earth. It is currently traveling towards the south-southeast through the constellations of Sagittarius and Corona Australis and is near magnitude 13.5; it will enter southern circumpolar skies by the end of this month and will pass within 10 degrees of the South Celestial Pole – still at 15th magnitude – in mid-September.
AUGUST 24, 2261: Comet 109P/Swift-Tuttle, the parent comet of the Perseid meteors, will pass 0.147 AU from Earth and should become a bright and conspicuous naked-eye object.
AUGUST 25, 1865: A 5-kg meteorite falls to the ground near the town of Shergotty (now Sherghati) in northeastern India. The Shergotty meteorite is now known to have come from Mars and is the prototype of the largest sub-classification of Martian meteorites.
AUGUST 25, 2003: NASA’s Spitzer Space Telescope is launched from Cape Canaveral, Florida. Spitzer, which was retired from service earlier this year, examined the universe in the infrared, and throughout its lifetime it observed numerous comets and performed many important examinations of them.
AUGUST 26, 2020: The main-belt asteroid (30523) 2001 MK23 will occult the 7th-magnitude star HD 22317 in Taurus. The predicted path of the occultation crosses central Algeria, the islands of Sardinia and Corsica, northern Italy, far eastern Switzerland, central Germany, far western Denmark, the southern tip of Norway, and southern Greenland.
AUGUST 28, 1758: While examining the comet of that year – Comet de la Nux C/1758 K1 – the French astronomer Charles Messier notices a diffuse object in the same field of view, which did not move from night to night. This was the object now known as the Crab Nebula, and it inspired Messier, who would later become the top comet-discovering astronomer of his time, to compile a catalog of deep-sky objects that might otherwise distract him and other comet-hunters. Messier’s brightest comet is this week’s “Comet of the Week.”
AUGUST 28, 1993: While traversing the main asteroid belt, NASA’s Galileo spacecraft passes by the asteroid (243) Ida. The images returned by Galileo reveal the presence of a small moon, since named Dactyl, orbiting around Ida. This was the first confirmed discovery of a moon accompanying an asteroid, and these objects are discussed in a future “Special Topics” presentation.
AUGUST 28, 2020: The first-known and largest main-belt asteroid, (1) Ceres – also a “dwarf planet” – will be at opposition. It is currently traveling towards the west-southwest through southern Aquarius and is slightly brighter than 8th magnitude.
AUGUST 29, 2011: Astronomers at Mauna Kea Observatory in Hawaii discover the asteroid 2011 QF99, which was later identified as being the first-known “Uranus Trojan” asteroid – of only two that are known so far. Trojan asteroids are the subject of a future “Special Topics” presentation.