Asteroid 1846 Bengt Honors Danish Astrophysicist Bengt Strömgren

Summary: Asteroid 1846 Bengt honors Danish astrophysicist Bengt Strömgren, who critically studied stellar interiors, stellar atmospheres and interstellar gas.

1957 photograph of Bengt Strömgren by Roger Higgins / World Telegram & Sun; New York World-Telegram and the Sun Newspaper Photograph Collection, Library of Congress Prints and Photographs Division, Washington, D.C: Public Domain, via Library of Congress (LOC)

Asteroid 1846 Bengt honors Danish astrophysicist Bengt Strömgren, who is recognized for his theoretical models of stellar interiors, stellar atmospheres and interstellar gas.

Asteroid 1846 Bengt was discovered during the Palomar-Leiden Survey (PLS) of 1960. The California Institute of Technology's (Caltech) Palomar Observatory in northern San Diego County, southwestern California, and Leiden Observatory (Dutch: Sterrewacht Leiden), South Holland, northwestern Netherlands, collaborated on the astronomical survey of faint minor planets. The survey's principal investigators were Dutch husband-and-wife astronomers Cornelis "Kees" Johannes van Houten (Feb. 18, 1920-Aug. 24, 2002) and Ingrid van Houten-Groeneveld (Oct. 21, 1921-March 30, 2015) and Dutch-American astronomer Anton "Tom" M.J. Gehrels (Feb. 21, 1925-July 11, 2011).

Gehrels conducted the photographic portion of the survey over 11 nights with Palomar's 48-inch Samuel Oschin telescope. Six dates in September (23 through 28) and five in October (16, 21, 23, 24, 25) yielded 130 photographic plates. The plates were then shipped to the van Houtens at Leiden University's Observatory for analysis.

Discovery of the asteroid now named 1846 Bengt is credited to all three principal investigators. The International Astronomical Union's (IAU) Minor Planet Center website details three identifications at Palomar Observatory on Saturday, Sept. 24, 1960: 1960 09 24.32430 Universal Time (UT) (00:46:59.52 a.m., Pacific Daylight Time), 1960 09 24.35000 UT (01:24:00.00 a.m., PDT) and 1960 09 24.35002 UT (01:24:01.73 a.m., PDT).

The van Houstens-Gehrels' discovery received the provisional designation of 6553 P-L. The P-L identified Palomar and Leiden as the discovery observatories.

An alternate designation of 1951 CW1 references a first observation by the University of Texas at Austin's McDonald Observatory, located near Fort Davis, in Jeff Davis County, Far West Texas. McDonald Observatory's observation was made 1951 02 10.2931 UT (1:02 a.m., Saturday, Feb. 10, 1951, Central Standard Time), according to the IAU Minor Planet Center website.

A second alternate designation 1957 YP references three observations made Friday, Dec. 27, 1957, by Goethe Link Observatory, sited near Brooklyn, Morgan County, south central Indiana. Goethe Link Observatory's observations occurred 1957 12 27.41 (4:50:24 a.m., Eastern Standard Time), 1957 12 27.41173 (4:52:53.47 a.m., EST) and 1957 12 27.44982 (5:47:44.45 a.m., EST), according to the IAU Minor Planet Center website.

Minor Planet Circular 4547, published Nov. 1, 1978, announced 1846 Bengt as the official designation of 6553 P-L. The announcement noted that the 70th birthday of "renowned Danish astronomer" Bengt Strömgren occasioned naming the asteroid in his honor.

Asteroid 1846 Bengt orbits in the solar system's asteroid belt. Also known as main asteroid belt or main belt, the asteroid belt lies between the orbits of Mars and Jupiter.

The asteroid has a diameter of 10.998 kilometers, according to the NASA (National Aeronautics and Space Administration) Jet Propulsion Laboratory (JPL) website. The assigned diameter has a sigma (standard deviation) of 0.080.

The main belt asteroid requires 3.58 years, according to the Minor Planet Center website. Its orbit marks aphelion, or farthest distance from the sun, at 2.670 au. (The International Astronomical Union defines an astronomical unit as exactly 149,597,870,700 meters. The unit approximates the average distance between Earth and the sun.)

Perihelion, or nearest point to the sun, measures 2.0092846. Perihelion most recently occurred Sunday, Sept. 16, 2018, at 01:18:56.45 a.m. UT (2018-09-16.05482; Saturday, Sept. 15, at 9:18:56.45 p.m., Eastern Daylight Time).

The asteroid's path places it closer to Earth and Mars than to Jupiter. Asteroid 1846 has a minimum orbit intersection distance (MOID) of 1.0288 au from Earth, 0.40199 au from the Red Planet's orbit and 2.492 au from Jupiter's orbit, according to the IAU Minor Planet Center website.

Asteroid 1846 Bengt's eponym (Ancient Greek: ἐπί, epí, “upon” + ὄνυμα, ónuma, “name”) was 20th-century Danish astrophysicist Bengt Georg Daniel Strömgren (Jan. 21, 1908-July 4, 1987). Strömgren's numerous "outstanding contributions" to the new field of theoretical astrophysics were recognized in his obituary, published by American theoretical physicist Lyman Spitzer Jr. (June 26, 1914-March 31, 1997) in the March 1988 issue of Physics Today. Spitzer noted Strömgren's pioneer studies of the internal composition and structure of stars, interpretations of stellar atmospheres via observed spectra and interstellar gas composition and structure. Strömgren spheres references Strömgren's theoretical models of luminous spheres of ionized hydrogen around hot stars that exist in the Milky Way and other galaxies.

The takeaways for asteroid 1846 Bengt honoring Danish astrophysicist Bengt Strömgren are that the main belt asteroid was discovered Sept. 24, 1960, by the three principal investigators of the Palomar-Leiden Survey; that 1846 Bengt's location in the main belt between Mars and Jupiter places it closer to Earth and Mars than to Jupiter; and that 1846 Bengt's eponym, Bengt Strömgren, pioneered astrophysical studies of the luminous spheres of ionized hydrogen that are known as Strömgren spheres.

Asteroid 1846 Bengt's most recent perihelion occurred 2018-09-16.05482 (01:18:56.45 a.m., Sunday, Sept. 16, 2018): Courtesy NASA/JPL-Caltech, via NASA JPL Solar System Dynamics

Acknowledgment

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

Image credits:

1957 photograph of Bengt Strömgren by Roger Higgins / World Telegram & Sun; New York World-Telegram and the Sun Newspaper Photograph Collection, Library of Congress Prints and Photographs Division, Washington, D.C: Public Domain, via Library of Congress (LOC) @ https://www.loc.gov/pictures/item/2001695997/

Asteroid 1846 Bengt's most recent perihelion occurred 2018-09-16.05482 (01:18:56.45 a.m., Sunday, Sept. 16, 2018): Courtesy NASA/JPL-Caltech, via NASA JPL Solar System Dynamics @ https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2001846;orb=1;cov=0;log=0;cad=0#orb

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