Subamara is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements.^[5][6] It orbits the Sun in the outer asteroid belt at a distance of 2.7–3.4 AU once every 5 years and 4 months (1,944 days; semi-major axis of 3.05 AU). Its orbit has an eccentricity of 0.12 and an inclination of 9° with respect to the ecliptic.^[4]

The asteroid was first observed as A905 UL (1905 UL) at Heidelberg Observatory in October 1905, where the body's observation arc begins a few days later on 1 November 1905, or 16 years prior to its official discovery observation at Vienna Observatory on 27 October 1921.^[1]

This minor planet was named for the Latin "very bitter" (combining sub and amara), most likely referring to the increasingly poor observing conditions due to light pollution at the Vienna Observatory in the early 1920s. The author of the Dictionary of Minor Planet Names learned about the naming circumstances from A. Schnell, who found clues in an article by Palisa published in the journal Astronomische Nachrichten in 1924 (AN 222, 172). In this article, Palisa complains about the bad weather and the light pollution caused by the continued operation of arc lamps at Ringstreet in Vienna's Währing district, where the observatory is located. Remembering a particular night in August 1923, Palisa was unable to visually find asteroid 995 Sternberga with his large 27-inch telescope. When he learnt that the same asteroid was easily spotted at Heidelberg Observatory despite using a telescope with a much smaller aperture of only 12-inch, he first thought of his declining eyesight before realizing, it was due in fact to the city's increasing light pollution, and that the time has come to relocated the Vienna Observatory elsewhere.^[3][12]

In the SDSS-based taxonomy, Subamara is a common, stony S-type asteroid.^[6][11]

Rotation period edit

Over four nights in January 2013, a rotational lightcurve of Subamara was obtained from photometric observations by Michael Alkema at the Elephant Head Observatory (G35) in Arizona. Lightcurve analysis gave a well-defined rotation period of 6.868±0.001 hours with a brightness variation of 0.25±0.02 magnitude (U=3).^[10]

James Folberth and colleges of the Rose-Hulman Institute of Technology previously observed this asteroid at Oakley Southern Sky Observatory (E09) in August 2011, finding a period of 6.864±0.004 hours with an amplitude of 0.11±0.02 magnitude (U=2).^[13] In November 2017, Tom Polakis at the Command Module Observatory (V02) in Tempe, Arizona, determined 6.8695±0.0012 hours with an amplitude of 0.12±0.03 magnitude (U=2).^[14]

Diameter and albedo edit

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer and the Japanese Akari satellite, Subamara measures 19.835±0.536 and 21.23±1.17 kilometers in diameter and its surface has an albedo of 0.236±0.027 and 0.171±0.020, respectively.^[7][8]

An earlier published measurement by the WISE team gives larger mean-diameter of 20.266±0.505 and an albedo of 0.2264±0.0199.^[9] The Collaborative Asteroid Lightcurve Link assumes a standard albedo for a stony S-type asteroid of 0.20 and calculates a diameter of 20.56 kilometers based on an absolute magnitude of 10.8.^[9]

• Lightcurve Database Query (LCDB), at www.minorplanet.info
• Dictionary of Minor Planet Names, Google books
• Asteroids and comets rotation curves, CdR – Geneva Observatory, Raoul Behrend
• Discovery Circumstances: Numbered Minor Planets (1)-(5000) – Minor Planet Center
• 964 Subamara at AstDyS-2, Asteroids—Dynamic Site
  • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
• 964 Subamara at the JPL Small-Body Database  
  • Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters