Arne Slettebak | |
|---|---|
 Slettebak in 1970 | |
| Born | (1925-08-08)August 8, 1925 |
| Died | May 20, 1999(1999-05-20) (aged 73) Worthington, Ohio, United States |
| Citizenship | United States (1932–1999) |
| Alma mater | University of Chicago (BS,PhD) |
| Spouse | |
| Children | 2 |
| Scientific career | |
| Fields | Astronomy |
| Institutions | |
| Thesis | On the Axial Rotation of the Brighter O and B Stars (1949) |
| Doctoral advisor | William Wilson Morgan |
Arne Edwin Slettebak (August 8, 1925 – May 20, 1999) was an Americanastronomer who served as chair of the astronomy department at theOhio State University from 1962 to 1987 and director of thePerkins Observatory from 1959 to 1978.
Slettebak was born in theFree City of Danzig before emigrating to the United States at a young age. He obtained a degree in physics in 1945 and hisdoctorate in astronomy in 1949, the latter under the supervision ofWilliam Wilson Morgan with a thesis onO-type andB-type stars. Slettebak joined theOhio State University shortly after graduating and was instrumental in re-establishing a separate astronomy department there. His principal research interests were instellar rotation andBe stars, and he published over 90 papers, abstracts and articles.
The main-belt asteroid9001 Slettebak, discovered in 1981, was named in his honour.
Arne Edwin[1] Slettebak was born in theFree City of Danzig (in modern-dayGdańsk, Poland) on August 8, 1925, to Norwegian parents.[2] His family emigrated to the United States in 1927, and he gained American citizenship in 1932.[2] He studied at theUniversity of Chicago, graduating with aBS degree in physics in 1945 and obtaining aPhD in astronomy in 1949.[2] His doctoral dissertation, which he completed under the guidance ofWilliam Wilson Morgan, was concerned with the rotational velocities ofO-type andB-type stars.[3][4] As a graduate student, he worked as a research assistant at theYerkes Observatory conductingastronomical spectroscopy investigations.[5] He also contributed to parts of what became theMorgan-Keenan system together with Morgan's other doctoral studentsNancy Grace Roman andWilliam P. Bidelman.[6]
After receiving his PhD, Slettebak joined theOhio State University as an instructor the same year.[2] He became assistant professor in 1950 and held aFulbright fellowship at theHamburg Observatory for the 1955–56 academic year, where he conducted research on the structures of galaxies.[5]
He was promoted to associate professor in 1958 and then full professor in 1959 when he assumed the role of director of thePerkins Observatory from Geoffrey Keller;[7][8] he would hold this position until 1978.[2] Also in 1959, he took over directorship of theMcMillin Observatory fromJ. Allen Hynek.[7][9]
Slettebak was a major force in the re-establishment of a separate astronomy department, which was approved in November 1962.[10] He became chair of the newly independent entity and remained in this position until 1987.[2] From 1964 to 1968, he supervised the department's move from the McMillin Observatory, whose building had been deemed too small and unsafe, and Orton Hall to its current location at the Smith Physics Laboratory.[a][9][12]
He also helped forge an agreement between the Ohio State University,Ohio Wesleyan University andLowell Observatory to move the Perkins Observatory's 69-inchreflecting telescope to Lowell inFlagstaff, Arizona.[2] A 16-inchSchmidt telescope and a 32-inch reflector were donated to Perkins and replaced the 69-inch telescope.[13] After its transfer, the telescope's optics were upgraded to a 72-inch mirror and it was used jointly by the two universities and the observatory.[b][2][15] It continued serving as the primary research instrument for Ohio State's astronomy department until 1998.[c][2]
Slettebak held anotherFulbright fellowship for the 1974–75 academic year, this time at theUniversity of Vienna.[18] During his career, he also undertook visiting professorships in Vienna andStrasbourg.[2] He was a councilor of theAmerican Astronomical Society from 1964 to 1967 and served on several commissions of theInternational Astronomical Union, including as president of Commission 45 (Stellar Classification) from 1979 to 1982.[2][19]
From 1961 to 1978, Slettebak represented Ohio State on the board of directors of theAssociation of Universities for Research in Astronomy, and was chair of its scientific committee between 1970 and 1973.[2][20] He retired from the astronomy department in 1994, becoming professor emeritus.[2] In 2015, the Ohio State Universityplanetarium was renamed the Arne Slettebak Planetarium in honour of his legacy.[12]
Slettebak's main research interests werestellar rotation, spectroscopy and the study ofBe stars; for the latter subject, he organised multiple colloquia at the International Astronomical Union.[2]
The topic of stellar rotation had been in a 'golden age' during the 1930s afterOtto Struve and his collaborators provided conclusive observational evidence for axial rotation in single stars.[21][22] However, afterPol Swings determined that the axial rotation ofbinary stars close to each other and with short periods tends to be approximately or perfectly synchronized with orbital motion, the field was abandoned for nearly 15 years.[23]
AfterWorld War II, interest in measurements of stellar axial rotation was revitalised by Slettebak, who published a series of papers on the topic starting in 1949.[24][25] He made extensive measurements of the rotational velocities of stars, initially making use of Struve andGrigory Shajn's graphical model during the 1950s and 60s,[24] and subsequently with numerical models.[2][26] One of his research projects was conducted jointly withCase Institute of Technology and sponsored by theOffice of Naval Research.[5]
Slettebak measured Be stars with axial rotational velocities of over 400–500 km/s, which averaged 150 km/s more thanB-type stars as a class.[27][28] He discovered groups of stars that had very low rotational velocities,[29] and also found both that starsat a later stage of their life were slower thandwarf stars and thatmetallic-line stars had much smaller rotational velocities than average dwarf stars.[30] Slettebak's data was used byAllan Sandage to show that the lower rotational velocities above the main sequence were consistent with theories of stellar evolution.[31]
Later in his career, Slettebak compiled the main results of statistical studies on stellar rotation conducted between 1930 and 1970, determining that the distribution of rotational velocities for stars along themain sequence increases from low values inF-type stars to a maximum in B-type stars.[28]
In 1955 and 1958, he conducted research in astronomical spectroscopy at theMount Wilson andPalomar observatories inCalifornia.[5] Slettebak remained active in research even after retirement, publishing the last of his more than 90 papers, abstracts and articles in 1998.[2][12]
Slettebak married Constance Lorraine Pixler, a music graduate from theCollege of Wooster, on August 28, 1949;[1] the couple had a daughter and a son.[32] He died on May 20, 1999, at the age of 73 inWorthington, Ohio, after a brief illness.[2][32] Pixler died in 2006 at the age of 82.[33]
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