1691 Oort

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Rare-type carbonaceous Themistian asteroid

title: "1691 Oort" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["themis-asteroids", "discoveries-by-karl-wilhelm-reinmuth", "discoveries-by-ingrid-van-houten-groeneveld", "named-minor-planets", "jan-oort", "cu-type-asteroids-(tholen)", "astronomical-objects-discovered-in-1956"] description: "Rare-type carbonaceous Themistian asteroid" topic_path: "general/themis-asteroids" source: "https://en.wikipedia.org/wiki/1691_Oort" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Rare-type carbonaceous Themistian asteroid ::

::data[format=table title="Infobox planet"]

Field	Value
minorplanet	yes
name	1691 Oort
background	#D6D6D6
image	1691Oort (Lightcurve Inversion).png
caption
discovery_ref
discovered	9 September 1956
discoverer	K. Reinmuth
I. Groeneveld
discovery_site	Heidelberg Obs.
mpc_name	(1691) Oort
alt_names	1956 RB1945 TD
1947 DA1950 PZ
1950 RU1951 XW
1955 MW1956 SD
1964 DAA917 TD
named_after	Jan Oort (astronomer)
mp_category	main-belt Themis
orbit_ref
epoch	4 September 2017 (JD 2458000.5)
uncertainty	0
observation_arc	71.42 yr (26,086 days)
aphelion	3.7153 AU
perihelion	2.6084 AU
semimajor	3.1618 AU
eccentricity	0.1750
period	5.62 yr (2,054 days)
mean_anomaly	240.25°
inclination	1.0860°
asc_node	174.55°
arg_peri	232.69°
dimensions	27.13 km (calculated)
km

km | | rotation | h h | | albedo |

km | rotation = h h | albedo =

0.10 (assumed) | spectral_type = Tholen = CUCU B–V = 0.682 U–B = 0.316 | abs_magnitude = 10.95

1691 Oort, provisional designation , is a rare-type carbonaceous Themistian asteroid from the outer region of the asteroid belt, approximately 33 kilometers in diameter.

It was discovered on 9 September 1956, by German astronomer Karl Reinmuth and Dutch astronomer Ingrid van Houten-Groeneveld at Heidelberg Observatory in south-west Germany. It was later named after Dutch astronomer Jan Oort.

Orbit and classification

is a member of the Themis family, a dynamical family of outer-belt asteroids with nearly coplanar ecliptical orbits. Oort orbits the Sun at a distance of 2.6–3.7 AU once every 5 years and 7 months (2,054 days). Its orbit has an eccentricity of 0.18 and an inclination of 1° with respect to the ecliptic.

It was first identified as at Turku in 1945, extending body's observation arc by 14 years prior to its official discovery observation. Information about an earlier 1917-identification, , is not available.

Physical characteristics

The dark C-type asteroid, classified as a rare intermediate CU-type in the Tholen taxonomy.

Rotation period

In February 2009, a rotational lightcurve of Oort was obtained from photometric observations taken by French amateur astronomer René Roy. It gave a well-defined rotation period of 10.2705 hours with a brightness variation of 0.38 magnitude (). An international study from 2013, published a concurring, modeled period of 10.2684 hours (n.a.).

Diameter and albedo

According to the surveys carried out by the Japanese Akari satellite and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Oort measures 33.64 and 37.37 kilometers in diameter, and its surface has an albedo of 0.065 and 0.053, respectively. The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.10 and calculates a diameter of 27.13 kilometers with an absolute magnitude of 10.95.

Naming

This minor planet was named in honor of Dutch astronomer Jan Oort (1900–1992), director of the Leiden Observatory (1945–1970), president of the International Astronomical Union (1958–1961), and a well-known authority on stellar statistics and galactic structure.

He overturned the idea that the Sun was at the center of the Milky Way. The Oort cloud, the outermost gravitationally bound region of the Solar System, was also named after him. The official was published by the Minor Planet Center on 15 February 1970 (M.P.C. 3023).

References

|type = 2017-03-17 last obs. |title = JPL Small-Body Database Browser: 1691 Oort (1956 RB) |url = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2001691 |publisher = Jet Propulsion Laboratory |accessdate = 6 June 2017}}

|title = Dictionary of Minor Planet Names – (1691) Oort |last = Schmadel | first = Lutz D. |publisher = Springer Berlin Heidelberg |page = 134 |date = 2007 |isbn = 978-3-540-00238-3 |doi = 10.1007/978-3-540-29925-7_1692 |chapter = (1691) Oort }}

|title = 1691 Oort (1956 RB) |work = Minor Planet Center |url = https://www.minorplanetcenter.net/db_search/show_object?object_id=1691 |accessdate = 19 December 2016}}

|title = Dictionary of Minor Planet Names – Addendum to Fifth Edition (2006–2008) |year = 2009 |url = https://archive.org/details/dictionaryminorp2008schm |url-access = limited |chapter = Appendix – Publication Dates of the MPCs |last = Schmadel |first=Lutz D. |publisher = Springer Berlin Heidelberg |page = 221 |isbn = 978-3-642-01964-7 |doi = 10.1007/978-3-642-01965-4}}

|title = Asteroids and comets rotation curves – (1691) Oort |last = Behrend |first = Raoul |publisher = Geneva Observatory |url = http://obswww.unige.ch/~behrend/page4cou.html#001691 |accessdate = 19 December 2016}}

|title = LCDB Data for (1691) Oort |publisher = Asteroid Lightcurve Database (LCDB) |url = http://www.minorplanet.info/PHP/generateOneAsteroidInfo.php?AstInfo=1691%7COort |accessdate = 19 December 2016}}

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|display-authors = 6 |first1 = Joseph R. |last1 = Masiero |first2 = T. |last2 = Grav |first3 = A. K. |last3 = Mainzer |first4 = C. R. |last4 = Nugent |first5 = J. M. |last5 = Bauer |first6 = R. |last6 = Stevenson |first7 = S. |last7 = Sonnett |date = August 2014 |title = Main-belt Asteroids with WISE/NEOWISE: Near-infrared Albedos |url = http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=2014ApJ...791..121M |journal = The Astrophysical Journal |volume = 791 |issue = 2 |page = 11 |bibcode = 2014ApJ...791..121M |doi = 10.1088/0004-637X/791/2/121 |arxiv = 1406.6645 |access-date= 19 December 2016}}

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