1777 Gehrels

1777 GehrelsDiscovery[1]

Discovered by| C. J. van Houten
I. van Houten-G.
T. Gehrels
Discovery site| Palomar Obs.
Discovery date| 24 September 1960
Designations

MPC designation

| (1777) Gehrels
Named after| Tom Gehrels (astronomer)[2]

Alternative designations

| 4007 P-L * 1937 GN
1941 BU * 1951 QB
1958 DA * A905 UE
A923 AA
Minor planet category| main-belt * (middle) [3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc| 111.43 yr (40,699 days)
|{{{apsis}}}|helion}}| 2.6705 AU
|{{{apsis}}}|helion}}| 2.5810 AU

Semi-major axis

| 2.6258 AU
Eccentricity| 0.0171
Orbital period| 4.25 yr (1,554 days)
Mean anomaly| 37.596°
Mean motion| 0° 13m 53.76s / day
Inclination| 3.1476°
Longitude of ascending node| 334.69°

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

| 131.12°
Physical characteristics
Dimensions| 11.860±0.184[4]
12.486±0.228 km[5]
12.667 km[6]
12.67 km (taken)[3]
13.14±1.25 km[7]
Rotation period| 2.83±0.05 h[8]
2.83552±0.00001 h[8]
2.8356±0.0002 h[lower-alpha 1][lower-alpha 2]
2.8356±0.0001 h[lower-alpha 1]
2.8358±0.0001 h[9]
2.836±0.001 h[10]
2.837±0.002 h[8]
2.840±0.004 h[11][lower-alpha 3]
Geometric albedo| 0.2151[6]
0.2212±0.0170[5]
0.244±0.013[4]
0.277±0.274[7]

Spectral type

| SMASS = Sq[1] * S[3]
Absolute magnitude (H)| 11.42[7] * 11.6[1] * 11.77±0.03[lower-alpha 1] * 11.773±0.03[3][6] * 11.78[5] * 11.78±0.05[11]

1777 Gehrels, also designated 4007 P-L, is a stony asteroid from the middle region of the asteroid belt, approximately 13 kilometers in diameter. It was discovered during the Palomar–Leiden survey in 1960, and named for astronomer Tom Gehrels, one of the survey's principal investigators and credited discoverer.

## Contents

* 1 Discovery
* 2 Orbit and classification
* 3 Physical characteristics
* 3.1 Diameter and albedo
* 3.2 Lightcurves
* 4 Naming
* 5 Notes
* 6 References
* 7 External links

## Discovery

Gehrels was discovered during the Palomar–Leiden survey by the Dutch astronomer couple Ingrid and Cornelis van Houten, in collaboration with Dutch–American astronomer Tom Gehrels at Palomar Observatory, California, on 24 September 1960.[12]

The survey designation "P-L" stands for Palomar–Leiden, named after Palomar and Leiden Observatory, which collaborated on the fruitful Palomar–Leiden survey in the 1960s. Gehrels used Palomar's Samuel Oschin telescope (also known as the 48-inch Schmidt Telescope), and shipped the photographic plates to Ingrid and Cornelis van Houten at Leiden Observatory, where astrometry was carried out. The trio are credited with the discovery of several thousand minor planets.[13]

## Orbit and classification

It orbits the Sun in the central main-belt at a distance of 2.6–2.7 AU once every 4 years and 3 months (1,554 days). Its orbit has an eccentricity of 0.02 and an inclination of 3° with respect to the ecliptic.[1]

First observed as A905 UE at Heidelberg Observatory in 1905, Gehrels' first used observation was made at Goethe Link Observatory in 1958, extending the body's observation arc by 2 years prior to its official discovery at Palomar.[12]

## Physical characteristics

This S-type asteroid is characterized as a transitional Sq-type in the SMASS classification.[1]

### Diameter and albedo

According to the survey carried out by NASA's Wide-field Infrared Survey Explorer (WISE) with its subsequent NEOWISE mission, Gehrels measures between 11.860 and 13.14 kilometers in diameter and its surface has an albedo between 0.2212 and 0.277.[4][5][7]

The Collaborative Asteroid Lightcurve Link adopts Petr Pravec's revised WISE-data and takes an albedo of 0.2151 with a diameter of 12.67 kilometers based on an absolute magnitude of 11.773.[3][6]

### Lightcurves

Several rotational lightcurve of Gehrels were obtained from photometric observations by astronomers Wiesław Wiśniewski, Petr Pravec, Pierre Antonini, Raoul Behrend, Donn Starkey, Laurent Bernasconi, Jacques Montier, Serge Heterier, Daniel Klinglesmith and Robert Stephens. Lightcurve analysis gave a rotation period between 2.83 and 2.840 hours with a brightness variation of 0.21 and 0.27 magnitude ({{{1}}}).[8][9][10][11][lower-alpha 1][lower-alpha 2][lower-alpha 3]

## Naming

This minor planet was named in honor of Dutch-born American astronomer Tom Gehrels (1925–2011), professor at the University of Arizona, staff member of the LPL research center at Tucson, a principal investigator in the Pioneer program, receiver of the Masursky Award, initiator of the Spacewatch project, and co-discoverer of thousands of minor planets in the Palomar–Leiden survey (see above). He was a pioneer in the field of photometric and polarimetric observations of Solar System bodies in the 1950s.[2][14] The official naming citation was published by the Minor Planet Center on 25 September 1971 (M.P.C. 3185).[15]

## Notes

1. ↑ 1.0 1.1 1.2 1.3 Pravec (2005) web: rotation period 2.8356±0.0002 hours with a brightness amplitude of 0.23 mag. Pravec (1990) web:rotation period 2.8356±0.0001 hours with a brightness amplitude of 0.21 mag. Summary figures at Collaborative Asteroid Lightcurve Link (CALL) for (1777) Gehrels
2. ↑ 2.0 2.1 Lightcurve plot A and lightcurve plot B by Petr Pravec (2005) from Ondrejov data obtained by the NEO Photometric Program and collaborating projects
3. ↑ 3.0 3.1 Lightcurve plot by Petr Pravec from re-analysis of the Wisniewski et al. (1997) data

## References

1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 "JPL Small-Body Database Browser: 1777 Gehrels (4007 P-L)". Jet Propulsion Laboratory. https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2001777. Retrieved 8 June 2017.
2. ↑ 2.0 2.1 Schmadel, Lutz D. (2007). "(1777) Gehrels". Dictionary of Minor Planet Names – (1777) Gehrels. Springer Berlin Heidelberg. p. 142. doi:10.1007/978-3-540-29925-7_1778. ISBN 978-3-540-00238-3.
3. ↑ 3.0 3.1 3.2 3.3 3.4 "LCDB Data for (1777) Gehrels". Asteroid Lightcurve Database (LCDB). http://www.minorplanet.info/PHP/generateOneAsteroidInfo.php?AstInfo=1777|Gehrels. Retrieved 15 May 2016.
4. ↑ 4.0 4.1 4.2 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 8 December 2016.
5. ↑ 5.0 5.1 5.2 5.3 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. http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=2011ApJ...741...90M. Retrieved 15 May 2016.
6. ↑ 6.0 6.1 6.2 6.3 Pravec, Petr; Harris, Alan W.; Kusnirák, Peter; Galád, Adrián; Hornoch, Kamil (September 2012). "Absolute magnitudes of asteroids and a revision of asteroid albedo estimates from WISE thermal observations". Icarus 221 (1): 365–387. doi:10.1016/j.icarus.2012.07.026. Bibcode: 2012Icar..221..365P. http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=2012Icar..221..365P. Retrieved 17 November 2015.
7. ↑ 7.0 7.1 7.2 7.3 Masiero, Joseph R.; Mainzer, A. K.; Grav, T.; Bauer, J. M.; Cutri, R. M.; Nugent, C. et al. (November 2012). "Preliminary Analysis of WISE/NEOWISE 3-Band Cryogenic and Post-cryogenic Observations of Main Belt Asteroids". The Astrophysical Journal Letters 759 (1): 5. doi:10.1088/2041-8205/759/1/L8. Bibcode: 2012ApJ...759L...8M. http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=2012ApJ...759L...8M. Retrieved 15 May 2016.
8. ↑ 8.0 8.1 8.2 8.3 Behrend, Raoul. "Asteroids and comets rotation curves – (1777) Gehrels". Geneva Observatory. http://obswww.unige.ch/~behrend/page4cou.html#001777. Retrieved 15 May 2016.
9. ↑ 9.0 9.1 Stephens, Robert D. (September 2005). "Asteroid lightcurve photometry from Santana Observatory - winter 2005". The Minor Planet Bulletin 32 (3): 66–68. ISSN 1052-8091. Bibcode: 2005MPBu...32...66S. http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=2005MPBu...32...66S. Retrieved 17 November 2015.
10. ↑ 10.0 10.1 Klinglesmith, Daniel A., III (April 2017). "Spin-Shape Model Lightcurves". The Minor Planet Bulletin 44 (2): 127–129. ISSN 1052-8091. Bibcode: 2017MPBu...44..127K. http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=2017MPBu...44..127K. Retrieved 8 June 2017.
11. ↑ 11.0 11.1 11.2 Wisniewski, W. Z.; Michalowski, T. M.; Harris, A. W.; McMillan, R. S. (March 1995). "Photoelectric Observations of 125 Asteroids". Abstracts of the Lunar and Planetary Science Conference 26: 1511. Bibcode: 1995LPI....26.1511W. http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=1995LPI....26.1511W. Retrieved 17 November 2015.
12. ↑ 12.0 12.1 "1777 Gehrels (4007 P-L)". Minor Planet Center. https://www.minorplanetcenter.net/db_search/show_object?object_id=1777. Retrieved 15 May 2016.
13. ↑ "Minor Planet Discoverers". Minor Planet Center. 24 April 2016. https://www.minorplanetcenter.net/iau/lists/MPDiscsNum.html. Retrieved 15 May 2016.
14. ↑ Jeff Harrison (12 July 2011). "Astronomer Tom Gehrels, 1925–2011". University of Arizona. http://uanews.org/story/astronomer-tom-gehrels-1925-2011. Retrieved 17 November 2015.
15. ↑ Schmadel, Lutz D.. "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.

## External links

* Lightcurve plot of 1777 Gehrels[Usurped!], Palmer Divide Observatory, B. D. Warner (2005)
* 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
* 1777 Gehrels at AstDyS-2, Asteroids—Dynamic Site
* Ephemeris * Observation prediction * Orbital info * Proper elements * Observational info
* 1777 Gehrels at the JPL Small-Body Database
* Close approach * Discovery * Ephemeris * Orbit diagram * Orbital elements * Physical parameters

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