1691 Oort

Lightcurve-based 3D-model of Oort

Discovery[1]
Discovered by| K. Reinmuth
I. Groeneveld
Discovery site| Heidelberg Obs.
Discovery date| 9 September 1956
Designations

MPC designation

| (1691) Oort
Named after| Jan Oort (astronomer)[2]

Alternative designations

| 1956 RB * 1945 TD
1947 DA * 1950 PZ
1950 RU * 1951 XW
1955 MW * 1956 SD
1964 DA * A917 TD
Minor planet category| main-belt * Themis[3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc| 71.42 yr (26,086 days)
|{{{apsis}}}|helion}}| 3.7153 AU
|{{{apsis}}}|helion}}| 2.6084 AU

Semi-major axis

| 3.1618 AU
Eccentricity| 0.1750
Orbital period| 5.62 yr (2,054 days)
Mean anomaly| 240.25°
Inclination| 1.0860°
Longitude of ascending node| 174.55°

|{{{apsis}}}|helion}}

| 232.69°
Physical characteristics
Dimensions| 27.13 km (calculated)[3]
33.163±0.534 km[4]
33.644±0.267[5]
37.37±0.74 km[6]
Rotation period| 10.2684±0.0005 h[7]
10.2705±0.0004 h[8]
Geometric albedo| 0.053±0.002[6]
0.065±0.011[5]
0.0672±0.0150[4]
0.10 (assumed)[3]

Spectral type

| Tholen = CU[1] * CU[3]
B–V = 0.682[1]
U–B = 0.316[1]
Absolute magnitude (H)| 10.90±0.12[9] * 10.95[1][3][4][6]

1691 Oort, provisional designation 1956 RB, 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.[10] It was later named after Dutch astronomer Jan Oort.[2]

## Contents

* 1 Orbit and classification
* 2 Physical characteristics
* 2.1 Rotation period
* 2.2 Diameter and albedo
* 3 Naming
* 4 References
* 5 External links

## 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.[1]

It was first identified as 1945 TD at Turku in 1945, extending body's observation arc by 14 years prior to its official discovery observation. Information about an earlier 1917-identification, A917 TD, is not available.[10]

## Physical characteristics

The dark C-type asteroid, classified as a rare intermediate CU-type in the Tholen taxonomy.[1]

### 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 ({{{1}}}).[8] An international study from 2013, published a concurring, modeled period of 10.2684 hours (n.a.).[7]

### 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.[4][5][6] 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.[3]

## 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.[2]

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 naming citation was published by the Minor Planet Center on 15 February 1970 (M.P.C. 3023).[11]

## References

1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 "JPL Small-Body Database Browser: 1691 Oort (1956 RB)". Jet Propulsion Laboratory. https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2001691. Retrieved 6 June 2017.
2. ↑ 2.0 2.1 2.2 Schmadel, Lutz D. (2007). "(1691) Oort". Dictionary of Minor Planet Names – (1691) Oort. Springer Berlin Heidelberg. p. 134. doi:10.1007/978-3-540-29925-7_1692. ISBN 978-3-540-00238-3.
3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 "LCDB Data for (1691) Oort". Asteroid Lightcurve Database (LCDB). http://www.minorplanet.info/PHP/generateOneAsteroidInfo.php?AstInfo=1691|Oort. Retrieved 19 December 2016.
4. ↑ 4.0 4.1 4.2 4.3 Mainzer, A.; Grav, T.; Masiero, J.; Hand, E.; Bauer, J.; Tholen, D. et al. (November 2011). "NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results". The Astrophysical Journal 741 (2): 25. doi:10.1088/0004-637X/741/2/90. Bibcode: 2011ApJ...741...90M.
5. ↑ 5.0 5.1 5.2 Masiero, Joseph R.; Grav, T.; Mainzer, A. K.; Nugent, C. R.; Bauer, J. M.; Stevenson, R. et al. (August 2014). "Main-belt Asteroids with WISE/NEOWISE: Near-infrared Albedos". The Astrophysical Journal 791 (2): 11. doi:10.1088/0004-637X/791/2/121. Bibcode: 2014ApJ...791..121M. http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=2014ApJ...791..121M. Retrieved 19 December 2016.
6. ↑ 6.0 6.1 6.2 6.3 Usui, Fumihiko; Kuroda, Daisuke; Müller, Thomas G.; Hasegawa, Sunao; Ishiguro, Masateru; Ootsubo, Takafumi et al. (October 2011). "Asteroid Catalog Using Akari: AKARI/IRC Mid-Infrared Asteroid Survey". Publications of the Astronomical Society of Japan 63 (5): 1117–1138. doi:10.1093/pasj/63.5.1117. Bibcode: 2011PASJ...63.1117U. (online, AcuA catalog p. 153)
7. ↑ 7.0 7.1 Hanus, J.; Broz, M.; Durech, J.; Warner, B. D.; Brinsfield, J.; Durkee, R. et al. (November 2013). "An anisotropic distribution of spin vectors in asteroid families". Astronomy and Astrophysics 559: 19. doi:10.1051/0004-6361/201321993. Bibcode: 2013A&A...559A.134H. http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=2013A&A...559A.134H. Retrieved 19 December 2016.
8. ↑ 8.0 8.1 Behrend, Raoul. "Asteroids and comets rotation curves – (1691) Oort". Geneva Observatory. http://obswww.unige.ch/~behrend/page4cou.html#001691. Retrieved 19 December 2016.
9. ↑ Veres, Peter; Jedicke, Robert; Fitzsimmons, Alan; Denneau, Larry; Granvik, Mikael; Bolin, Bryce et al. (November 2015). "Absolute magnitudes and slope parameters for 250,000 asteroids observed by Pan-STARRS PS1 - Preliminary results". Icarus 261: 34–47. doi:10.1016/j.icarus.2015.08.007. Bibcode: 2015Icar..261...34V. http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=2015Icar..261...34V. Retrieved 19 December 2016.
10. ↑ 10.0 10.1 "1691 Oort (1956 RB)". Minor Planet Center. https://www.minorplanetcenter.net/db_search/show_object?object_id=1691. Retrieved 19 December 2016.
11. ↑ Schmadel, Lutz D. (2009). "Appendix – Publication Dates of the MPCs". Dictionary of Minor Planet Names – Addendum to Fifth Edition (2006–2008). Springer Berlin Heidelberg. p. 221. doi:10.1007/978-3-642-01965-4. ISBN 978-3-642-01964-7. https://archive.org/details/dictionaryminorp2008schm.

## External links

* Asteroid Lightcurve Database (LCDB), query form (info )
* Dictionary of Minor Planet Names, Google books
* Asteroids and comets rotation curves, CdR – Observatoire de Genève, Raoul Behrend
* Discovery Circumstances: Numbered Minor Planets (1)-(5000) – Minor Planet Center
* 1691 Oort at AstDyS-2, Asteroids—Dynamic Site
* Ephemeris * Observation prediction * Orbital info * Proper elements * Observational info
* 1691 Oort at the JPL Small-Body Database
* Close approach * Discovery * Ephemeris * Orbit diagram * Orbital elements * Physical parameters

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