In this month: August 2022

13th August 1898

The asteroid Eros is discovered by German astronomer Gustav Witt. With an approximate diameter of 16.8 kilometres and a rotation period of 5.27 hours it orbits in an eccentric orbit between Mars and Earth travelling mainly inside the orbit of Mars. Eros is famous as the first asteroid to be orbited by a spacecraft, and the first asteroid to have a spacecraft land on it when the NEAR Shoemaker spacecraft made a soft landing on the asteroid’s surface in 2001 sending back over 160,000 images during the encounter. Eros was 315 million kilometres from Earth at the time. Eros is named for the god of love in Greek mythology.

Image: An artist's rendering of NASA's Near Earth Asteroid Rendezvous (NEAR) spacecraft at asteroid Eros. NASA

29th August 1975

Japanese astronomer, Minoru Honda, is the first to observe the nova V1500 Cygni (or Nova Cygni 1975), in the constellation of Cygnus, shining at an apparent brightness of magnitude 3.0. This was the second highest brightness of any nova of the 20th century, exceeded only by CP Puppis in 1942. The nova had brightened to magnitude 1.7 on the next day, and then rapidly faded. It remained visible to the naked eye for about a week, and 680 days after reaching maximum the star had dimmed by 12.5 magnitudes. V1500 Cygni consists of a white dwarf primary star and a red dwarf secondary star. In 1977 its distance was calculated to be 6,360 light years away.

Image courtesy National Geographic.

8th August 1989

The Hipparcos mission is launched by ESA from their launch site in Kourou, French Guiana. It was the first mission dedicated to establishing highly accurate positions and precise distance measurements of more than one hundred thousand stars. It carried out its measurements in a highly elliptical 10-hour orbit, ranging between 500 kilometres and 36,000 kilometres above the Earth's surface. Originally planned for an operational lifetime of two and a half years the mission lasted more than four years before being decommissioned on the 15th August 1993.

The word "Hipparcos" is an acronym for HIgh Precision PARallax COllecting Satellite and also a reference to the ancient Greek astronomer Hipparchus of Nicaea, who is noted for applications of trigonometry to astronomy and his discovery of the precession of the equinoxes.

Artist image courtesy NASA Science.

BORN

13th August 1822, Heinrich Louis d'Arrest, (a.k.a. Heinrich Ludwig d'Arrest), German astronomer.

While still a student at the University of Berlin, d'Arrest was part of the team led by Johann Gottfried Galle in the search for Neptune. Working from French astronomer Le Verrier's calculations they found the planet on the 23rd September 1846. His later work at the Leipzig Observatory, Germany, led him, in 1851, to discover the comet named for him. He also studied asteroids and galaxies, discovering NGC 1 in 1861 and NGC 26 and NGC 358 in 1865. He won the Gold Medal of the Royal Astronomical Society in 1875. The crater d’Arrest on the Moon, the crater d’Arrest on the Martian satellite Phobos, as well as the asteroid 9133 d'Arrest are named after him.

Image: NASA/JPL-Caltech, taken by Voyager 2, 1989.

8th August 1920, Bernard Yarnton Mills. Australian engineer and internationally recognised as a pioneer of radio astronomy in Australia.

In 1948 he commenced working with the CSIRO's newly formed radio astronomy group where he designed and implemented the Mills Cross Telescope at Badgerys Creek, west of Sydney. It produced the first survey of the southern radio sky and had a major impact in establishing Australia as a leader in the new science of radio astronomy.

Mills left the CSIRO in 1960 to establish a radio astronomy group in the School of Physics at the University of Sydney where he designed and built the Molonglo Cross Telescope, thirty kilometres east of Canberra. It became operational in 1967. The major achievement was the Molonglo Reference Catalogue of 12,000 radio sources which led to the discovery of some of the first pulsars in the southern hemisphere. In 1976 Bernard Mills was awarded the Companion of the Order of Australia (AC), but refused to accept it from the then Governor General Sir John Kerr, waiting until Kerr's resignation before accepting. He was awarded the Grote Reber Award in 2006 for his lifetime contribution to astronomy.

Image: Mills hammering in the positioning stake at the Parkes Radio telescope site, courtesy Mills family archive via an extensive Royal Society publication.

26th August 1918, Katharine Johnson. American mathematician.

During her thirty three year career at NASA her calculations of orbital mechanics were critical to the success of the first and subsequent U.S. crewed spaceflights. She earned a reputation for mastering complex manual calculations and helped pioneer the use of computers to perform tasks. The space agency noted her "historical role as one of the first African-American women to work as a NASA scientist". The 2016 movie Hidden Figures portrays Johnson and other female African-American mathematicians who worked at NASA. She spent her later years encouraging students to enter the fields of science, technology, engineering, and mathematics (STEM).

Among her many awards were the Presidential Medal of Freedom in 2015 and the Congressional Gold Medal awarded in 2019 by the United States Congress. In 2021, she was inducted into the American National Women's Hall of Fame.

Image: Katherine Johnson at her desk, 1966. Courtesy NASA