Gerald Kron
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Gerald Kron (April 6, 1913 – April 9, 2012) was an American astronomer who was one of the pioneers of high-precision
photometry Photometry can refer to: * Photometry (optics), the science of measurement of visible light in terms of its perceived brightness to human vision * Photometry (astronomy), the measurement of the flux or intensity of an astronomical object's electr ...
with photoelectric instrumentation. He discovered the first starspot and made the first photometric observation of a stellar flare. A graduate of the
University of Wisconsin-Madison A university () is an institution of tertiary education and research which awards academic degrees in several academic disciplines. ''University'' is derived from the Latin phrase , which roughly means "community of teachers and scholars". Uni ...
, where he earned a
Master of Science A Master of Science (; abbreviated MS, M.S., MSc, M.Sc., SM, S.M., ScM or Sc.M.) is a master's degree. In contrast to the Master of Arts degree, the Master of Science degree is typically granted for studies in sciences, engineering and medici ...
degree in
mechanical engineering Mechanical engineering is the study of physical machines and mechanism (engineering), mechanisms that may involve force and movement. It is an engineering branch that combines engineering physics and engineering mathematics, mathematics principl ...
in 1934, Kron became interested in
astronomy Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest includ ...
, which he studied under Joel Stebbins. Stebbins arranged for Kron to enter the
University of California at Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California), is a public land-grant research university in Berkeley, California, United States. Founded in 1868 and named after the Anglo-Irish philosopher George Berkele ...
, where he received his doctorate in astronomy in 1938. During
World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
, Kron served with the
Radiation Laboratory The Radiation Laboratory, commonly called the Rad Lab, was a microwave and radar research laboratory located at the Massachusetts Institute of Technology (MIT) in Cambridge, Massachusetts. It was first created in October 1940 and operated until 3 ...
at the
Massachusetts Institute of Technology The Massachusetts Institute of Technology (MIT) is a Private university, private research university in Cambridge, Massachusetts, United States. Established in 1861, MIT has played a significant role in the development of many areas of moder ...
, and participated in the development of microwave radar. He later became the head of the Special Devices Group at the Naval Ordnance Test Station (NOTS) at Inyokern, California, where he conducted studies on solid fuel rockets, and developed radio
transponder In telecommunications, a transponder is a device that, upon receiving a signal, emits a different signal in response. The term is a blend of ''transmitter'' and ''responder''. In air navigation or radio frequency identification, a flight trans ...
s for the
Manhattan Project The Manhattan Project was a research and development program undertaken during World War II to produce the first nuclear weapons. It was led by the United States in collaboration with the United Kingdom and Canada. From 1942 to 1946, the ...
's
Project Camel Project Camel encompassed the work performed by the California Institute of Technology (Caltech) in support of the Manhattan Project during World War II. These activities included the development of detonators and other equipment, testing of bomb ...
. After the war Kron returned to the
Lick Observatory The Lick Observatory is an astronomical observatory owned and operated by the University of California. It is on the summit of Mount Hamilton (California), Mount Hamilton, in the Diablo Range just east of San Jose, California, United States. The ...
, where he was one of the designers of the C. Donald Shane telescope. Using photometric techniques that he had pioneered before the war, he studied the stars, especially
eclipsing binaries A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved as separate stars us ...
. In 1965, Kron became director of the
United States Naval Observatory The United States Naval Observatory (USNO) is a scientific and military facility that produces geopositioning, navigation and timekeeping data for the United States Navy and the United States Department of Defense. Established in 1830 as the ...
in
Flagstaff, Arizona Flagstaff ( ), known locally as Flag, is the county seat of Coconino County, Arizona, in the southwestern United States. As of the 2020 United States census, the city's population was 76,831. Flagstaff is the principal city of the Coconino Cou ...
, and he was a regular visitor to the
Australian National University The Australian National University (ANU) is a public university, public research university and member of the Group of Eight (Australian universities), Group of Eight, located in Canberra, the capital of Australia. Its main campus in Acton, A ...
's Mount Stromlo Observatory.


Early life

Gerald Edward Kron was born in
Milwaukee Milwaukee is the List of cities in Wisconsin, most populous city in the U.S. state of Wisconsin. Located on the western shore of Lake Michigan, it is the List of United States cities by population, 31st-most populous city in the United States ...
on 6 April 1913, the son of Edmund Kron, a mechanic, and his wife Letty Dieterick Kron. He attended Lincoln High School in Milwaukee, and then
University of Wisconsin-Madison A university () is an institution of tertiary education and research which awards academic degrees in several academic disciplines. ''University'' is derived from the Latin phrase , which roughly means "community of teachers and scholars". Uni ...
, where he earned a
Master of Science A Master of Science (; abbreviated MS, M.S., MSc, M.Sc., SM, S.M., ScM or Sc.M.) is a master's degree. In contrast to the Master of Arts degree, the Master of Science degree is typically granted for studies in sciences, engineering and medici ...
degree in
mechanical engineering Mechanical engineering is the study of physical machines and mechanism (engineering), mechanisms that may involve force and movement. It is an engineering branch that combines engineering physics and engineering mathematics, mathematics principl ...
in 1934. While there took advantage of the access to machine shops as part of his training to design and build a 6-inch telescope. After graduation, he received a scholarship to study
astronomy Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest includ ...
for two years under Joel Stebbins. He published his first paper in 1935, a study of the photometric elements of Boss 5070, an
eclipsing binary A binary star or binary star system is a Star system, system of two stars that are gravity, gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved ...
. In 1935, Kron travelled to California with Stebbins and Albert Whitford, where Kron and Whitford assisted Stebbins at the
Mount Wilson Observatory The Mount Wilson Observatory (MWO) is an Observatory#Astronomical observatories, astronomical observatory in Los Angeles County, California, United States. The MWO is located on Mount Wilson (California), Mount Wilson, a peak in the San Gabrie ...
. After returning to Madison, he worked with Whitford on the design of a 200-inch telescope. Stebbins arranged for Kron to enter the
University of California at Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California), is a public land-grant research university in Berkeley, California, United States. Founded in 1868 and named after the Anglo-Irish philosopher George Berkele ...
, where he received his doctorate in astronomy in 1938, with a thesis on the photometric elements of eclipsing binaries. He then worked in the
Lick Observatory The Lick Observatory is an astronomical observatory owned and operated by the University of California. It is on the summit of Mount Hamilton (California), Mount Hamilton, in the Diablo Range just east of San Jose, California, United States. The ...
as a research assistant.


World War II

In May 1940 Kron joined the
Radiation Laboratory The Radiation Laboratory, commonly called the Rad Lab, was a microwave and radar research laboratory located at the Massachusetts Institute of Technology (MIT) in Cambridge, Massachusetts. It was first created in October 1940 and operated until 3 ...
at the
Massachusetts Institute of Technology The Massachusetts Institute of Technology (MIT) is a Private university, private research university in Cambridge, Massachusetts, United States. Established in 1861, MIT has played a significant role in the development of many areas of moder ...
, and participated in the development of microwave radar. He would later use devices and equipment that he became familiar with at the Radiation Laboratory such as the RCA IP21
photomultiplier A photomultiplier is a device that converts incident photons into an electrical signal. Kinds of photomultiplier include: * Photomultiplier tube, a vacuum tube converting incident photons into an electric signal. Photomultiplier tubes (PMTs for sh ...
and Direct-coupled amplifiers in looking at the stars. Later in
World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
he became head of the Special Devices Group at the Naval Ordnance Test Station (NOTS) at Inyokern, California, where he conducted studies on solid fuel rockets. He also participated in the
Manhattan Project The Manhattan Project was a research and development program undertaken during World War II to produce the first nuclear weapons. It was led by the United States in collaboration with the United Kingdom and Canada. From 1942 to 1946, the ...
's
Project Camel Project Camel encompassed the work performed by the California Institute of Technology (Caltech) in support of the Manhattan Project during World War II. These activities included the development of detonators and other equipment, testing of bomb ...
, developing instrumentation to evaluate the test drops of nuclear bomb shapes. Radio
transponder In telecommunications, a transponder is a device that, upon receiving a signal, emits a different signal in response. The term is a blend of ''transmitter'' and ''responder''. In air navigation or radio frequency identification, a flight trans ...
s with timing pulses attached to the bombs allowed their position to be tracked the release of the bomb until the time it was all destroyed when the bomb detonated in the air or hit the ground. This gave the drop time to within a few hundredths of a second. In the course of his duties he visited Kingman and Wendover Army Air Fields. When the war ended, he "liberated" some equipment from NOTS before it could be destroyed.


Later life

After the war Kron returned to the Lick Observatory, where he was one of the designers and creators of the C. Donald Shane telescope. During the war, Kron met Katherine Carson Gordon, a
Vassar College Vassar College ( ) is a private liberal arts college in Poughkeepsie, New York, United States. Founded in 1861 by Matthew Vassar, it was the second degree-granting institution of higher education for women in the United States. The college be ...
graduate and a Radcliff College student, at a picnic at
Oak Ridge, Tennessee Oak Ridge is a city in Anderson County, Tennessee, Anderson and Roane County, Tennessee, Roane counties in the East Tennessee, eastern part of the U.S. state of Tennessee, about west of downtown Knoxville, Tennessee, Knoxville. Oak Ridge's po ...
. After the war, she became an assistant at Lick Observatory. He married her on 22 April 1946. She continued publishing papers under her maiden name. The two worked together, looking at eclipsing binaries. At one point they found an irregularity, which they attributed to an area of colder temperature, a starspot. His observation and explanation were correct, but he was ahead of his time. It would be many years before the existence of starspots was accepted, and they became a popular research topic. They also made the first photometric observation of a stellar flare. In 1965, Kron became director of the
United States Naval Observatory The United States Naval Observatory (USNO) is a scientific and military facility that produces geopositioning, navigation and timekeeping data for the United States Navy and the United States Department of Defense. Established in 1830 as the ...
in
Flagstaff, Arizona Flagstaff ( ), known locally as Flag, is the county seat of Coconino County, Arizona, in the southwestern United States. As of the 2020 United States census, the city's population was 76,831. Flagstaff is the principal city of the Coconino Cou ...
. He regularly visited
Canberra Canberra ( ; ) is the capital city of Australia. Founded following the Federation of Australia, federation of the colonies of Australia as the seat of government for the new nation, it is Australia's list of cities in Australia, largest in ...
in Australia, where the Mount Stromlo Observatory allowed him to study M-type dwarf stars in the southern sky. He was senior research fellow at the
Australian National University The Australian National University (ANU) is a public university, public research university and member of the Group of Eight (Australian universities), Group of Eight, located in Canberra, the capital of Australia. Its main campus in Acton, A ...
in Canberra from 1974 to 1976. He retired in 1985 to live in
Honolulu Honolulu ( ; ) is the List of capitals in the United States, capital and most populous city of the U.S. state of Hawaii, located in the Pacific Ocean. It is the county seat of the Consolidated city-county, consolidated City and County of Honol ...
, but moved to
Sedona, Arizona Sedona ( ) is a city that straddles the county line between Coconino County, Arizona, Coconino and Yavapai County, Arizona, Yavapai counties in the northern Verde Valley region of the U.S. state of Arizona. As of the 2010 United States Census, ...
, in 1995. Kron served for a time as President of the Astronomical Society of the Pacific, and the International Astronomical Union's Commission on Instrumentation. He was elected a Fellow of the
Royal Astronomical Society The Royal Astronomical Society (RAS) is a learned society and charitable organisation, charity that encourages and promotes the study of astronomy, planetary science, solar-system science, geophysics and closely related branches of science. Its ...
. Kron published over 130 scientific papers, many of them described the method accurately measure the light of stars and globular clusters. He pioneered the use of photomultiplier tubes to measure the infrared radiation of cold stars. His measurements of
globular cluster A globular cluster is a spheroidal conglomeration of stars that is bound together by gravity, with a higher concentration of stars towards its center. It can contain anywhere from tens of thousands to many millions of member stars, all orbiting ...
s in the
Large Magellanic Cloud The Large Magellanic Cloud (LMC) is a dwarf galaxy and satellite galaxy of the Milky Way. At a distance of around , the LMC is the second- or third-closest galaxy to the Milky Way, after the Sagittarius Dwarf Spheroidal Galaxy, Sagittarius Dwarf ...
revised earlier views on distances outside the
Milky Way Galaxy The Milky Way or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galaxy, which are ...
. He died on 12 April 2012. His wife Katherine and son Donald predeceased him. He was survived by his brother Robert and his remaining four children, Richard, Jenny, Virginia and Charles.


Notes


References

* {{DEFAULTSORT:Kron, Gerald 1913 births 2012 deaths Scientists from Milwaukee University of California, Berkeley alumni University of Wisconsin–Madison College of Engineering alumni Manhattan Project people American astronomers Fellows of the Royal Astronomical Society