This Week in History: October 18-24

Ice and Stone 2020: Week 43 Content

OCTOBER 18, 1977: Charles Kowal discovers the first-known centaur, (2060) Chiron, with the 1.2-meter Schmidt telescope at Palomar Observatory in California. Centaurs are the subject of a previous “Special Topics” presentation. 

OCTOBER 18, 1989: NASA’s Galileo mission is deployed from the Space Shuttle Atlantis, with its final destination being Jupiter. While en route to Jupiter Galileo made the first spacecraft flybys of asteroids, (951) Gaspra in 1991 and (243) Ida in 1993 – discovering the moon Dactyl orbiting around Ida in the process – and also observed some of the impacts of Comet Shoemaker-Levy 9 into Jupiter in July 1994. 

The Galileo spacecraft and its attached Inertial Upper Stage booster are released from the payload bay of Atlantis on October 18, 1989. Courtesy NASA.

OCTOBER 19, 2011: A team led by Carey Lisse of John Hopkins University’s Applied Physics Laboratory announces that they have detected evidence of cometary impacts into forming planets around the star Eta Corvi in infrared data taken by the Spitzer Space Telescope. This is analogous to the period of Late Heavy Bombardment in our solar system – discussed in a future “Special Topics” presentation – and the Eta Corvi results are discussed in a previous “Special Topics” presentation on “exocomets.” 

OCTOBER 19, 2014: Comet Siding Spring C/2013 A1 passes just 0.00094 AU – one-third of a lunar distance – from Mars, and is observed by spacecraft in Mars orbit and on the surface. It is this week’s “Comet of the Week.” 

OCTOBER 19, 2017: The Pan-STARRS survey program in Hawaii discovers the object now designated as 1I/‘Oumuamua, the first-known object from interstellar space to pass through our solar system. ‘Oumuamua is the subject of this week’s “Special Topics” presentation. 

OCTOBER 19, 2020: The Amor-type asteroid (159402) 1999 AP10 will pass 0.081 AU from Earth. It is currently near magnitude 12.5 and is traveling northward through the constellations of Lacerta, Cygnus, and Cepheus; on November 3 it passes within 1½ degrees of the North Celestial Pole but will have faded to magnitude 13.5 by then. 

OCTOBER 20, 2010: Comet 103P/Hartley 2 passes 0.121 AU from Earth, reaching a peak brightness of 5th magnitude. Two weeks later the comet was encountered by NASA’s EPOXI mission, and this event is described in a previous “Special Topics” presentation. 

OCTOBER 20, 2020: NASA’s OSIRIS-REx mission is expected to extract soil samples from the “Nightingale” site on the near-Earth asteroid (101955) Bennu, for eventual return to Earth in 2023. The OSIRIS-REx mission is discussed in a future “Special Topics” presentation. 

OCTOBER 20, 2020: The recently-discovered Comet NEOWISE C/2020 P1 will pass through perihelion at a heliocentric distance of 0.342 AU. If it survives its perihelion passage it should become visible in the northern hemisphere’s morning sky late this month, possibly bright enough to detect in binoculars. Information about Comet NEOWISE can be found at the Comet Resource Center. 

OCTOBER 20, 2020: The main-belt asteroid (71733) 2000 JQ47 will occult the 7th-magnitude star HD 756 in Andromeda. The predicted path of the occultation crosses northwestern Ukraine, far southwestern Belarus, northeastern Poland, northern Denmark, northern Scotland, far southeastern Canada including Newfoundland and New Brunswick, the eastern U.S. from Maine to Louisiana, and central Mexico. 

OCTOBER 21, 1965: Comet Ikeya-Seki 1965f, the brightest comet to appear during the 20th Century, passes through perihelion at a heliocentric distance of 0.008 AU. Comet Ikeya-Seki was a Kreutz sungrazer – the subject of next week’s “Special Topics” presentation – and it is also next week’s “Comet of the Week.” 

OCTOBER 21, 2003: A team led by Michael Brown of CalTech obtains the discovery images of the world now known as (136199) Eris with the 1.2-meter Schmidt telescope at Palomar Observatory in California, although the images were not recognized at first and the discovery was not announced until July 2005. Eris turns out to be just smaller than Pluto in size although more massive than Pluto, and was responsible for forcing the issue of what is and what is not a “planet;” it is now listed as a “dwarf planet.” The Kuiper Belt, within which Eris orbits, and the definition of “planet,” are discussed in previous “Special Topics” presentations. 

OCTOBER 21, 2015: Cameras aboard ESA’s Rosetta mission detect a tiny moon orbiting the nucleus of Comet 67P/Churyumov-Gerasimenko. Dubbed “Churyumoon,” this object orbited the nucleus for two days before disappearing. Comet 67P is a previous “Comet of the Week.” 

OCTOBER 21, 2020: The Orionid meteor shower, which is associated with Comet 1P/Halley, will be at its peak. The Orionids normally exhibit a peak rate of 20 to 25 meteors per hour. The moon will be a few days past its “new moon” phase and thus viewing conditions for the Orionids are good this year. 

OCTOBER 22, 2023: Comet 2P/Encke will pass through perihelion at a heliocentric distance of 0.340 AU. This year’s return of 2P/Encke, during which it was visible from the southern hemisphere after perihelion, is a previous “Comet of the Week;” in 2023 the comet will be moderately well-placed from the northern hemisphere and should reach 7th magnitude in early October before disappearing into morning twilight. 

OCTOBER 22, 2183: Comet 9P/Tempel 1 will pass just 0.02 AU from Mars. This is the only comet to have been encountered by spacecraft on two different returns and it is a previous “Comet of the Week.” 

OCTOBER 23, 1924: Walter Baade at Bergedorf Observatory in Germany discovers the asteroid now known as (1036) Ganymed. Ganymed is an Amor-type asteroid and, with an average diameter of approximately 35 km, is the largest near-Earth asteroid. It and other near-Earth asteroids are discussed in the Week 2Special Topics” presentation. 

OCTOBER 23, 1992: A team led by Walter Slade of NASA’s Jet Propulsion Laboratory announces that, in radar data taken with NASA’s tracking antenna at Goldstone, California and with the Very Large Array radio telescope in New Mexico, they have detected evidence of water ice near Mercury’s north pole. The presence of ice near Mercury’s poles would be confirmed two decades later by NASA’s MESSENGER spacecraft, and its existence, and the significance of its presence, are discussed in a previous “Special Topics” presentation. 

OCTOBER 24, 1990: Comet Levy 1990c passes through perihelion at a heliocentric distance of 0.939 AU. Comet Levy was the first comet to be observed by the Hubble Space Telescope, and is a previous “Comet of the Week.” 

OCTOBER 24, 1998: NASA’s Deep Space 1 spacecraft, a technology testbed mission, is launched from Cape Canaveral, Florida. Deep Space 1 encountered the Mars-crossing asteroid (9969) Braille in July 1999 and Comet 19P/Borrelly in September 2001 and is discussed in a previous “Special Topics presentation. 

OCTOBER 24, 2007: Comet 17P/Holmes undergoes an outburst of almost 15 magnitudes, a brightness increase by a factor of 600,000 – the largest cometary outburst ever recorded. It is a future “Comet of the Week.” 

OCTOBER 24, 2020: The main-belt asteroid (1171) Rusthawelia will occult the 6th-magnitude star 29 Ceti. The predicted path of the occultation crosses central and eastern Russia (including Volgograd), far northern Kazakhstan, the Crimean peninsula, (including Sevastopol), eastern and southern Bulgaria, northern Greece (including Thessaloniki), southern Albania, far southwestern Italy including most of Sicily, northern Tunisia, northern Algeria, and eastern and southern Morocco. 

More from Week 43:

Comet of the Week    Special Topic     Bonus Content      Free PDF Download    Glossary

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