15224 Penttilä

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]

15224 Penttilä

Discovery[1]
Discovered by	E. Bowell
Discovery site	Anderson Mesa Stn.
Discovery date	15 May 1985
Designations
MPC designation	(15224) Penttilä
Named after	Antti Penttilä[1] (Finnish astronomer)
Alternative designations	1985 JG · 1970 HB 2000 HR19
Minor planet category	main-belt[1][2] · (inner) background[3][4]
Orbital characteristics[2]
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[5][6][7] 8.79±3.79 km[8] 9.60±2.05 km[9]
Synodic rotation period	4.377±0.001 h[10]
Geometric albedo	0.04–0.085[5][6][7][8][9]
Absolute magnitude (H)	13.80[5][7][8] 13.9[1][2][11] 14.13[9]

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]