HistoryIce and StoneWeek 28

This Week in History: July 5-11

Ice and Stone 2020: Week 28 Content

JULY 5, 1687: British physicist Isaac Newton publishes his Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy), usually known as the Principia, wherein he lays out what is now known as his Law of Universal Gravitation. Part of Newton’s work in the Principia was based upon his calculations of the Great Comet of 1680 – a future “Comet of the Week” – and his methodology was utilized by Edmond Halley to calculate the orbits of comets, including the one that now bears his name (1P/Halley), which is the subject of a previous “Special Topics” presentation. 

JULY 7, 1992: The comet that would later become known as Comet Shoemaker-Levy 9 passes just 43,000 km above the top of Jupiter’s atmosphere and is ripped apart into over 20 fragments by tidal forces from Jupiter’s gravity. The comet would be discovered a little over eight months later, and in July 1994 each of the fragments would impact Jupiter’s atmosphere. Comet Shoemaker-Levy 9 is next week’s “Comet of the Week.” 

JULY 7, 2017: A meteoroid, perhaps 30 cm in diameter, enters Earth’s atmosphere above southwestern Australia and, after traveling through the atmosphere for about 90 seconds, exits back into interplanetary space. An analysis of the observations indicates that the Earth’s gravitational influences placed the object into an orbit like that of a Jupiter-family comet that will cause it to make close approaches to Jupiter – the first to take place in early 2025 – that, over the next few hundred thousand years may eventually eject it from the solar system. 

JULY 8, 2020: The Apollo-type asteroid (242450) 2004 QY2 will pass 0.163 AU from Earth. It was brightest – about 14th magnitude – last week, and is still close to 15th magnitude, although it will fade rapidly over the coming weeks as it passes interior to Earth’s orbit. 

JULY 10, 1992: ESA’s Giotto spacecraft has a flyby encounter with Comet 26P/Grigg-Skjellerup. Giotto had previously passed by Comet 1P/Halley in 1986, and the mission as a whole, including the encounter with Comet Grigg-Skjellerup, is discussed in this week’s “Special Topics” presentation. 

JULY 10, 2010: While en route to Comet 67P/Churyumov-Gerasimenko, ESA’s Rosetta spacecraft flies by the main-belt asteroid (21) Lutetia. The Rosetta mission, including its encounters with main-belt asteroids, is discussed in this week’s “Special Topics” presentation. 

JULY 11, 2019: JAXA’s Hayabusa2 spacecraft, in orbit around the near-Earth asteroid (162173) Ryugu, successfully touches down on Ryugu’s surface and collects samples of sub-surface material. Hayabusa2, with its samples, is now en route back to Earth and is expected to return this coming December. The Hayabusa2 mission is discussed in a future “Special Topics” presentation.

Image of asteroid Ryugu taken by JAXA’s Hayabusa2 spacecraft with the small monitor camera (CAM-H) during a touchdown rehearsal operation on October 25, 2018. Courtesy of JAXA.

More from Week 28:

Comet of the Week    Special Topic    Free PDF Download    Glossary

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Author

  • Alan Hale

    Alan Hale was born in Tachikawa, Japan (as the son of a U.S. Air Force officer) but moved with his family later soon after to Alamogordo, New Mexico, where he spent his childhood years. Hale entered the Navy and graduated from the U.S. Naval Academy with a Bachelor’s Degree in Physics After leaving the service, he began working at the Jet Propulsion Laboratory on the Deep Space Network. While at JPL he was involved with several spacecraft projects, most notably the Voyager 2 encounter with the planet Uranus. Following that encounter, Hale left JPL and enrolled at New Mexico State University. He earned his Master’s Degree and then his Ph.D.. His thesis paper has become one of the seminal papers in early exoplanet research, with over 200 citations to date. He worked at the New Mexico Museum of Space History as its Staff Astronomer and Outreach Education Coordinator, before founding the Southwest Institute for Space Research (now known as the Earthrise Institute). He has developed and taught astronomy-related educational activities at the university level. Hale’s research interests include the search for planets beyond the solar system; stars like the sun; minor bodies in the solar system, especially comets and near-Earth asteroids; and advocacy of spaceflight. He is primarily known for his work with comets, which has included his discovery of Comet Hale-Bopp in 1995. In recent years he has worked to increase scientific collaboration between the U.S. and other nations, including Iran, Zimbabwe, and Lebanon. Hale lives in the Sacramento Mountains outside of Cloudcroft, New Mexico with his partner Vickie Moseley. He has two sons, Zachary and Tyler, both of whom have graduated from college. On clear nights he can often be found making observations of the latest comets or other astronomical phenomena.

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