Eleanor Helin Discovered Asteroid 4660 Nereus in February 1982

Summary: American astronomer Eleanor Helin discovered asteroid 4660 Nereus at northern San Diego County’s Palomar Observatory on Sunday, Feb. 28, 1982.

American astronomer Eleanor Helin discovered asteroid 4660 Nereus (1982 DB) by meticulously scanning a photographic plate with a magnifying lens; she was one of five women inducted into the Women in Science and Technology International (WITI) Hall of Fame on Thursday, June 25, 1998: WITI -- Women In Technology International @WITI, via Twitter Jan. 16, 2019

American astronomer Eleanor Helin discovered asteroid 4660 Nereus on Sunday, Feb. 28, 1982, at the California Institute of Technology’s (Caltech) Palomar Observatory in northern San Diego County’s Palomar Mountain Range.

Eleanor Francis “Glo” Helin (Nov. 19, 1932-Jan. 25, 2009) made her discovery while photographing split periodic comet 79P/du Toit-Harley, also known as du Toit 2, with Palomar Observatory’s Samuel Oschin telescope. Also called the Oschin Schmidt, the instrument is a 48-inch (1.22-meter) aperture Schmidt camera. As an astrophotographic telescope, the Oschin Schmidt lacks an eyepiece and functions only as a camera.

Helin’s discovery occurred approximately 36 days after the asteroid’s last close approach of the 20th century. According to the European Space Agency (ESA)-sponsored NEODyS-2 website, the Earth- and Mars-crosser had a near-pass of 0.027716 au (astronomical units) (4146254.58 kilometers) with Earth on Saturday, Jan. 23, 1982.

Helin described the circumstances of the discovery in two articles for The Planetary Society’s quarterly magazine, The Planetary Report. In “Discovering an Asteroid,” in The Planetary Report’s July/August 1982 issue, Helin recalled meeting with American astrogeologist and comet and minor planet discoverer Eugene Merle “Gene” Shoemaker (April 28, 1928-July 19, 1997) for a scheduled observing session, beginning Saturday, Feb. 27, and ending Tuesday, March 2, at Palomar Observatory. They were searching for faint periodic comets, distanced far enough away from the sun to allow for resolving and measuring their bare nuclei, or solid central cores. They also aimed to recover, or re-observe, Comet du Toit 2, which Helin described as “unusual in that it had split into two pieces,” in her second Nereus article, “The Recovery of 1982DB,” which appeared in The Planetary Report’s January/February 1991 issue.

Helin and Shoemaker set the 48-inch Schmidt telescope to track the comet at their first observation session. The observations began around 7:30 p.m., Saturday, Feb. 27, and continued until after 5 a.m., Sunday, Feb. 28. They obtained 10 plates from the session.

Clouds and rain set in later Sunday and continued through Monday, March 1. While scanning the plates on Sunday for objects of interest, Helin and Shoemaker made an independent rediscovery of 1863 Antinous. The stony Mars-crossing, Apollo asteroid was discovered Sunday, March 7, 1948 by American astronomer Carl Alvar Wirtanen (Nov. 11, 1910-March 7, 1990) at Lick Observatory on Mount Hamilton in west central California’s Santa Clara County. Apollo asteroids are Earth-crossers, with orbits crossing Earth’s orbit.

On Monday, March 1, while Shoemaker returned for his Monday class at Caltech (California Institute of Technology), Helin re-examined their 10 plates. By methodically scanning the comet du Toit 2 plate with a magnifying lens, she finally espied a long, finely etched trail “a little more than a centimeter away from the main component of the comet” (1982: 4).

In the early evening, after Shoemaker’s return, they examined their only record of the new asteroid, one plate of 50 minutes exposure. They determined an approximate position but they needed the direction of apparent motion as prograde (in the direction of planetary orbits around the sun) or retrograde (in the opposite direction).

Around midnight, the weather intermittently cleared. At about 2 a.m., Tuesday, March 2, they were able to obtain a short exposure. The asteroid’s absence from the plate supported a retrograde apparent motion.

British astronomer Brian G. Marsden (Aug. 5, 1937-Nov. 18, 2010), who served as director of the IAU’s Central Bureau for Astronomical Telegrams (CBAT) from 1968 to 1999, announced Helin’s discovery via International Astronomical Union Circular (IAUC) no. 3675 on March 5, 1982. His announcement stated that Helin had discovered “another fast-moving asteroidal object.” (In their website’s tribute to Helin, The Planetary Society, a space advocacy, non-governmental, nonprofit foundation based in Pasadena, California, credits Helin as discoverer or co-discoverer of 872 asteroids.)

In her recovery article in The Planetary Report’s January/February 1991 issue, Helin referenced the “curious phenomenon” of making an “unexpected discovery” while “searching for something else.” She stated that her February 1982 discovery “was another example of that curious phenomenon” (1991: 16).

The takeaways for Eleanor Helin’s discovery of asteroid 4660 Nereus in February 1982 are that the discovery came about while Helin and comet discoverer Gene Shoemaker were observing comet 79P/du Toit-Harley and that the asteroid appeared on one of only 10 plates that Helin and comet discoverer Gene Shoemaker were able to obtain during a weekend of adverse weather conditions at California’s Palomar Observatory.

Goldstone Solar System Radar’s (GSSR) Sunday, Jan. 20, 2002, delay-Doppler imaging of small Apollo asteroid 4660 Nereus, which was discovered Sunday, Feb. 28, 1982, by American astronomer Eleanor Helin: NASA/JPL (Jet Propulsion Laboratory), Public Domain, via Wikimedia Commons

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

American astronomer Eleanor Helin discovered asteroid 4660 Nereus (1982 DB) by meticulously scanning a photographic plate with a magnifying lens; she was one of five women inducted into the Women in Science and Technology International (WITI) Hall of Fame on Thursday, June 25, 1998: WITI -- Women In Technology International @WITI, via Twitter Jan. 16, 2019, @ https://twitter.com/WITI/status/1085594701053464576

Goldstone Solar System Radar’s (GSSR) Sunday, Jan. 20, 2002, delay-Doppler imaging of small Apollo asteroid 4660 Nereus, which was discovered Sunday, Feb. 28, 1982, by American astronomer Eleanor Helin: NASA/JPL (Jet Propulsion Laboratory), Public Domain, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Nereus.jpg

For further information:

Brozovic, Marina; Steven J. Ostro; Lance A.M. Benner; Jon D. Giorgini; Raymond F. Jurgens; Randy Rose; Michael C. Nolan; Alice A. Hine; Christopher Magri; Daniel J. Scheeres; and Jean-Luc Margot. “Radar Observations and a Physical Model of Asteroid 4660 Nereus, a Prime Space Mission Target.” Icarus, vol. 201, issue 1 (May 2009): 153-166.
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Available @ https://planetary.s3.amazonaws.com/assets/tpr/pdf/tpr-1991-v11n1.pdf

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Available @ https://planetary.s3.amazonaws.com/assets/tpr/pdf/tpr-1991-v11n1.pdf

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