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1615 Bardwell
Discovery
Discovered by	Indiana University; (Indiana Asteroid Program)
Discovery site	Goethe Link Obs.
Discovery date	28 January 1950
Designations
MPC designation	(1615) Bardwell
Named after	Conrad Bardwell (astronomer)
Alternative designations	1950 BW · 1926 TO; 1937 TJ · 1948 RB1; 1948 RH1 · 1948 TG
Minor planet category	main-belt · Themis
Orbital characteristics
	Epoch 4 September 2017 (JD 2458000.5)
	Uncertainty parameter 0
Observation arc	90.49 yr (33,053 days)
Aphelion	3.6887 AU
Perihelion	2.5664 AU
Semi-major axis	3.1275 AU
Eccentricity	0.1794
Orbital period (sidereal)	5.53 yr (2,020 days)
Mean anomaly	169.71°
Mean motion	0° 10m 41.52s / day
Inclination	1.6901°
Longitude of ascending node	152.55°
Argument of perihelion	252.97°
Physical characteristics
Dimensions	21.92±5.97 km; 25.01±1.49 km; 27.78±1.6 km (IRAS:5); 28.8±2.9 km; 29.139±0.148 km; 31±3 km; 31.579±0.250 km
Synodic rotation period	18 h
Geometric albedo	0.0497±0.0192; 0.05±0.01; 0.060±0.010; 0.0642±0.008 (IRAS:5); 0.079±0.015; 0.09±0.06
Spectral type	Tholen = B · B; B–V = 0.692; U–B = 0.329
Absolute magnitude (H)	11.38 · 11.46

1615 Bardwell, provisional designation 1950 BW, is a rare-type Themistian asteroid from the outer region of the asteroid belt, approximately 27 kilometers in diameter. It was discovered on 28 January 1950, by IU's Indiana Asteroid Program at Goethe Link Observatory near Brooklyn, Indiana, United States.^[11] It is named for American astronomer Conrad Bardwell.^[2]

Orbit and classification

Bardwell is a member of the Themis family, a dynamical family of outer-belt asteroids with nearly coplanar ecliptical orbits. It orbits the Sun at a distance of 2.6–3.7 AU once every 5 years and 6 months (2,020 days). Its orbit has an eccentricity of 0.18 and an inclination of 2° with respect to the ecliptic.^[1]

Its orbit has an eccentricity of 0.18 and an inclination of 2° with respect to the ecliptic.^[1] It was first identified as 1926 TO at Simeiz Observatory in 1926, extending the body's observation arc by 24 years prior to its official discovery observation.^[11]

Naming

This minor planet was named for Conrad M. Bardwell (1926–2010), who was a research associate at the Cincinnati Observatory and later associate director of the Minor Planet Center in Cambridge, Massachusetts, United States. Bardwell successfully established numerous identifications from observations in widely separated oppositions and provided observers with reliable data of orbital elements.^[2] The official naming citation was published by the Minor Planet Center on 15 June 1974 (M.P.C. 3643).^[12]

Physical characteristics

In the Tholen taxonomy, Bardwell is a blueish B-type asteroid, a rare subtype of the abundant carbonaceous C-types found in the outer belt. The spectra of B-type bodies show a broad absorption feature at one micron wavelength that is associated with the presence of magnetite and is what gives the asteroid its blue tint.^[13] There are only a few dozens asteroids of this type known to exist.^[14]

Rotation period

In the late 1970s, a rotational lightcurve of Bardwell was obtained by American astronomer Edward Tedesco. It gave a provisional rotation period of 18 hours with a change in brightness of 0.2 magnitude (U=1).^[a] As of 2017, no other photometric analysis of Bardwell has been made.

Diameter and albedo

According to the surveys carried out by the Infrared Astronomical Satellite IRAS and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Bardwell measures between 21.92 and 31.58 kilometers in diameter, and its surface has an albedo between 0.049 and 0.09.^[4]^[6]^[7]^[8]^[10] The Collaborative Asteroid Lightcurve Link agrees with the results obtained by IRAS, that is, an albedo of 0.0642 and a diameter of 27.78 kilometers based on an absolute magnitude of 11.38.^[3]

Notes

^ ^a ^b Tedesco, E.F. (1979) PhD Dissertation, New. Mex. State Univ. 280pp.; Rotation period of 18 hours with a brightness amplitude of 0.2. Summary figures at Asteroid Lightcurve Database for (1615) Bardwell