HistoryIce and StoneWeek 30

This Week in History: July 19-25

Ice and Stone 2020: Week 30 Content

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 the impacts of Comet Shoemaker-Levy 9 into Jupiter in 1994; that comet is last week’s “Comet of the Week.” 

JULY 20, 1963: The path of a total solar eclipse crosses southern Alaska, central Canada, and the far northeastern continental U.S. Astronomers Francois Dossin and Bert Donn, observing from Maine, report their discovery of a probable comet near the sun that appears on several photographs they took during totality. “Eclipse Comets” are the subject of a previous “Special Topics” presentation. 

JULY 22, 1960: American geologists Edward Chao and Eugene Shoemaker report their discovery of the mineral coesite at the site of the Barringer Crater (aka the Canyon Diablo Crater) near Winslow, Arizona, conclusively demonstrating its origin from an impact event. This was one of the first and best-established impact craters on Earth’s surface, which are discussed in next week’s “Special Topics” presentation. 

JULY 22, 1994: Nucleus “W” of Comet Shoemaker-Levy 9 impacts Jupiter, the last of over twenty nuclei that impacted that planet over the previous week. This comet was last week’s “Comet of the Week.” 

JULY 22, 2021: NASA’s Double Asteroid Redirection Test (DART) mission is scheduled for launch. DART’s destination is the binary Amor-type asteroid (65803) Didymos, where it will test asteroid deflection by impacting Didymos’ moon, which has just recently been given the name “Dimorphos.” The DART mission is discussed in a previous “Special Topics” presentation, while various deflection strategies are discussed in a future “Special Topics” presentation. 

Previously unseen image of Comet Hale-Boop that I photographed the evening of April 9, 1997, from my then-residence in Cloudcroft, New Mexico.

JULY 23, 1995: Shortly after midnight local time I discover an 11th-magnitude comet near the globular star cluster M70 in Sagittarius, and at around that same time an amateur astronomer in Arizona, Thomas Bopp, discovers the same comet. A little over a year and a half later Comet Hale-Bopp C/1995 O1 became one of the brightest comets of the second half of the 20th Century and was seen by more people than any other comet in history; up until this month it had been the most recent “Great Comet” for observers in the northern hemisphere. It is this week’s “Comet of the Week.” 

JULY 25, 2076: The outer solar system world (90377) Sedna will pass through perihelion at a heliocentric distance of 76.2 AU. Sedna and other objects in the outer solar system are discussed in a future “Special Topics” presentation. 

More from Week 30:

Comet of the Week    Special Topic    Free PDF Download    Glossary

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  • 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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