Arlo U. Landolt (1935–2022)

Arlo Landolt, one of the giants of observational astronomy in the 20th century whose photometric standards still enable astronomers to make accurate brightness measurements of objects of scientific interest, died on January 21, 2022. He was 86 years old. He is survived by his wife of 55 years, Eunice, five daughters, thirteen grandchildren, and 6 great-grandchildren.

Arlo Udell Landolt was born on September 29, 1935 in Highland, Illinois. He grew up on a farm and attended a one-room schoolhouse through the 8th grade. On cold winter mornings his mother would send him to school with a baked potato for each pocket to help keep him warm. He was the first member of his family to go to high school, let alone go to college. He got his undergraduate degree from Miami University in Ohio in 1955, and his Ph.D. from Indiana University in 1963. While he was a graduate student, Arlo had a life-changing experience when he was chosen to be part of the first scientific expedition to winter over at the South Pole during the International Geophysical Year in 1957. Arlo’s job was to take measurements of the aurora and airglow. He later described living at the South Pole, “In retrospect, it was just a miracle. It was just really fantastic.” When he returned to Indiana University, he finished his thesis on Cepheids in Open Clusters in 1962 with John Irwin. Arlo had already been hired by Louisiana State University before he defended his thesis. He was a professor at LSU until his retirement in 2003. He was the Ball Family Emeritus Professor of Physics & Astronomy.

Arlo’s early career coincided with the establishment of the National Observatories at Kitt Peak, Arizona, and Cerro Tololo in Chile. He was the first guest observer ever at Kitt Peak in 1959 and was among the first at Cerro Tololo in the mid-sixties. Arlo was honored in 2014 for 55 years of observing at the National Observatories.

Arlo developed photometric standards in the Johnson/Cousins UBVRI bands, publishing updates in 1983, 1992, 2007, 2009, 2013, and 2016. The later work on faint standards was done with his postdoc, James Clem. His classic 1992 paper, “UBVRI Photometric Standard Stars in the Magnitude Range 11.5 < V < 16.0 Around the Celestial Equator” has been cited over 4000 times [1]. This paper contains 526 standard stars centered on the Celestial Equator that are therefore available to telescopes in the northern and southern hemispheres providing “an internally consistent homogeneous broadband standard photometric system around the sky.” In obtaining the data necessary for the standard stars, Arlo spent at least 1500 nights observing at various telescopes at KPNO and CTIO! The “Landolt Standards” have been used to produce secondary and tertiary standards around the sky so almost all optical photometry of stars, novae, supernovae, QSOs etc. depends on these standards.

Arlo also published photometry of many variable stars during his long career, from the eclipsing binary V382 Cygni in 1964, to the hot R Coronae Borealis star, V348 Sgr in 2019. He published multiple papers on novae, supernovae, eclipsing binaries, and R Coronae Borealis stars. In 1964, he discovered the first known pulsating white dwarf, HL Tau 76, which has a period of 12.5 minutes, too long for radial oscillations. This discovery later led to the recognition of the ZZ Ceti variables as non-radial g-mode pulsators.

Arlo served as the Secretary of the AAS from 1980 to 1989 and from 1995 to 2004. He was also a great supporter of the American Association for Variable Star Observers and served four terms on the AAVSO Council/Board. He received the William Tyler Olcott Distinguished Service Award, presented to a member of the AAVSO organization for outstanding contributions in mentoring/promoting variable star astronomy.

In 1995, he received the George Van Biesbroeck Prize from the American Astronomical Society which honors a living individual for long-term extraordinary or unselfish service to astronomy, often beyond the requirements of his or her paid position. In 2015, Dr. Arlo Landolt was presented the Astronomical League’s Leslie C. Peltier Award “for his development of photometric stellar standards for use by professional and non-professionals alike, and his overall support for the astronomical community.” Landolt was elected a Legacy Fellow of the American Astronomical Society in 2020. A conference in his honor, “The Landolt Standards and 21st Century Photometry,” was held in 2015 at LSU. He received the LSU Distinguished Faculty Award in 1998.

Arlo’s long career stretched from the era of glass plates to photoelectric photometers to CCD cameras. Mt. Landolt in the Antarctic, the Landolt Astronomical Observatory in Nicholson Hall at LSU, and an asteroid, 15072 Landolt are named after him. He had the same season tickets to LSU football for 50 years.

In addition, at his last AAS meeting as Secretary (205th Meeting of the AAS, San Diego, January 2005), a cocktail was created in his honor:

THE LANDOLT STANDARD

• 2 parts mango rum

• 2 parts pineapple rum

• 1 part triple sec

• 3 parts cranberry juice

• 3 parts pineapple juice

• a wedge of pineapple for garnish

It’s no exaggeration to say Arlo was universally liked despite the terrible puns he loved to tell. He interacted with several generations of astronomers during his many observing runs and at AAS meetings. He was a great mentor and friend to us and many others. He is missed.

See also:

• Landolt’s AstroGen entry

• Landolt’s AIP Oral History interview

• Tributes to Landolt submitted on the AAS website