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15224 Penttilä
Discovery
Discovered by	E. Bowell
Discovery site	Anderson Mesa Stn.
Discovery date	15 May 1985
Designations
MPC designation	(15224) Penttilä
Named after	Antti Penttilä; (Finnish astronomer)
Alternative designations	1985 JG · 1970 HB; 2000 HR19
Minor planet category	main-belt · (inner); background
Orbital characteristics
	Epoch 27 April 2019 (JD 2458600.5)
	Uncertainty parameter 0
Observation arc	48.02 yr (17,539 d)
Aphelion	3.0019 AU
Perihelion	1.8313 AU
Semi-major axis	2.4166 AU
Eccentricity	0.2422
Orbital period (sidereal)	3.76 yr (1,372 d)
Mean anomaly	356.13°
Mean motion	0° 15m 44.64s / day
Inclination	12.350°
Longitude of ascending node	70.116°
Argument of perihelion	196.23°
Physical characteristics
Mean diameter	7.924±0.119 km; 8.79±3.79 km; 9.60±2.05 km
Synodic rotation period	4.377±0.001 h
Geometric albedo	0.04–0.085
Absolute magnitude (H)	13.80; 13.9; 14.13

15224 Penttilä, provisional designation 1985 JG, is a dark background asteroid from the inner regions of the asteroid belt, approximately 8 kilometers (5 miles) in diameter. It was discovered on 15 May 1985, by American astronomer Edward Bowell at Lowell's Anderson Mesa Station in Arizona, United States.^[1] The likely elongated asteroid has a rotation period of 4.4 hours.^[11] It was named after planetary scientist Antti Penttilä at the University of Helsinki.^[1]

Orbit and classification

Penttilä is a non-family asteroid from the main belt's background population.^[3]^[4] It orbits the Sun in the inner asteroid belt at a distance of 1.8–3.0 AU once every 3 years and 9 months (1,372 days; semi-major axis of 2.42 AU). Its orbit has an eccentricity of 0.24 and an inclination of 12° with respect to the ecliptic.^[2]

The body's observation arc begins with its first observation, a precovery taken at the Crimean Astrophysical Observatory in April 1970, or 15 years prior to its official discovery observation at Anderson Mesa Station.^[1]

Naming

This minor planet was named for Finnish postdoctoral researcher Antti Penttilä (born 1977) at the University of Helsinki, an expert on light reflection and absorption on the surface of small Solar System bodies such as asteroids and cometary nuclei, as well as of the cosmic dust released by cometary comae.^[1] The official naming citation was published on 12 July 2014 (M.P.C. 89081).^[12]

Physical characteristics

The asteroid's spectral type has not been determined.^[3] Due to its low geometric albedo, it likely a carbonaceous C-type asteroid (see below).

Rotation period

In June 2015, a rotational lightcurve was obtained for this asteroid from photometric observations by astronomer Daniel Klinglesmith at Etscorn Campus Observatory (719), New Mexico. Lightcurve analysis gave a rotation period of 4.377±0.001 hours with a brightness variation of 0.55 in magnitude (U=3-), indicative of a non-spherical, elongated shape.^[10] Previously, in August 2012, a concurring period of 4.3771±0.0064 hours with an amplitude of 0.46 was determined from observations in the R-band by astronomers at the Palomar Transient Factory, California (U=2).^[13]

Diameter and albedo

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Penttilä measures between 7.9 and 9.6 kilometers in diameter and its surface has an albedo between 0.04 and 0.085.^[5]^[6]^[7]^[8]^[9] The Collaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20, and hence calculates a smaller diameter of 4.9 kilometers.^[11]

References

^ ^a ^b ^c ^d ^e ^f ^g ^h "15224 Penttila (1985 JG)". Minor Planet Center. Retrieved 5 December 2018.
^ ^a ^b ^c ^d "JPL Small-Body Database Browser: 15224 Penttila (1985 JG)" (2018-05-04 last obs.). Jet Propulsion Laboratory. Retrieved 5 December 2018.
^ ^a ^b ^c "Asteroid 15224 Penttila". Small Bodies Data Ferret. Retrieved 5 December 2018.
^ ^a ^b "Asteroid (15224) Penttila – Proper elements". AstDyS-2, Asteroids – Dynamic Site. Retrieved 4 December 2018.
^ ^a ^b ^c ^d Mainzer, A. K.; Bauer, J. M.; Cutri, R. M.; Grav, T.; Kramer, E. A.; Masiero, J. R.; et al. (June 2016). "NEOWISE Diameters and Albedos V1.0". NASA Planetary Data System: EAR-A-COMPIL-5-NEOWISEDIAM-V1.0. Bibcode:2016PDSS..247.....M. Retrieved 5 December 2018.
^ ^a ^b ^c Masiero, Joseph R.; Mainzer, A. K.; Grav, T.; Bauer, J. M.; Cutri, R. M.; Dailey, J.; et al. (November 2011). "Main Belt Asteroids with WISE/NEOWISE. I. Preliminary Albedos and Diameters". The Astrophysical Journal. 741 (2): 20. arXiv:1109.4096. Bibcode:2011ApJ...741...68M. doi:10.1088/0004-637X/741/2/68. S2CID 118745497.
^ ^a ^b ^c ^d 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. arXiv:1109.6407. Bibcode:2011ApJ...741...90M. doi:10.1088/0004-637X/741/2/90. S2CID 35447010. (catalog)
^ ^a ^b ^c ^d 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. arXiv:1209.5794. Bibcode:2012ApJ...759L...8M. doi:10.1088/2041-8205/759/1/L8. S2CID 46350317.
^ ^a ^b ^c ^d Nugent, C. R.; Mainzer, A.; Bauer, J.; Cutri, R. M.; Kramer, E. A.; Grav, T.; et al. (September 2016). "NEOWISE Reactivation Mission Year Two: Asteroid Diameters and Albedos". The Astronomical Journal. 152 (3): 12. arXiv:1606.08923. Bibcode:2016AJ....152...63N. doi:10.3847/0004-6256/152/3/63.
^ ^a ^b Klinglesmith, Daniel A. III; Hanowell, Jesse; Hendrickx, Sebastian; Madden, Karl; Montgomery, Samuel (October 2015). "Asteroids Observed at Etscorn Observatory: 2015 April - June". The Minor Planet Bulletin. 42 (4): 251–252. Bibcode:2015MPBu...42..251K. ISSN 1052-8091.
^ ^a ^b ^c "LCDB Data for (15224) Penttilä". Asteroid Lightcurve Database (LCDB). Retrieved 5 December 2018.
^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 5 December 2018.
^ Waszczak, Adam; Chang, Chan-Kao; Ofek, Eran O.; Laher, Russ; Masci, Frank; Levitan, David; et al. (September 2015). "Asteroid Light Curves from the Palomar Transient Factory Survey: Rotation Periods and Phase Functions from Sparse Photometry". The Astronomical Journal. 150 (3): 35. arXiv:1504.04041. Bibcode:2015AJ....150...75W. doi:10.1088/0004-6256/150/3/75. S2CID 8342929.