3430 Bradfield

3430 Bradfield (prov. designation: 1980 TF₄) is a stony Agnia asteroid from the central regions of the asteroid belt, approximately 8 kilometers (5 miles) in diameter. It was discovered on 9 October 1980, by American astronomer Carolyn Shoemaker at the Palomar Observatory in California. The Sq-type asteroid was named after comet hunter William A. Bradfield.^[1]

3430 Bradfield

Shape model of Bradfield from its lightcurve
Discovery[1]
Discovered by	C. Shoemaker
Discovery site	Palomar Obs.
Discovery date	9 October 1980
Designations
MPC designation	(3430) Bradfield
Named after	William A. Bradfield (discoverer of comets)
Alternative designations	1980 TF4 · 1974 HY1 1976 YS7
Minor planet category	main-belt[1][2] · (middle) Agnia[3]
Orbital characteristics[2]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc	43.93 yr (16,044 d)
Aphelion	3.0293 AU
Perihelion	2.4890 AU
Semi-major axis	2.7592 AU
Eccentricity	0.0979
Orbital period (sidereal)	4.58 yr (1,674 d)
Mean anomaly	102.11°
Mean motion	0° 12m 54s / day
Inclination	4.4281°
Longitude of ascending node	43.225°
Argument of perihelion	278.60°
Physical characteristics
Mean diameter	8.492±0.263 km[4]
Geometric albedo	0.269±0.035[4]
Spectral type	SMASS = Sq[2]
Absolute magnitude (H)	12.5[1][2]

Orbit and classification

When applying the hierarchical clustering method to its proper orbital elements according to Nesvorný, Bradfield is a member of the Agnia family (514),^[3] a very large family of stony asteroids with more than 2000 known members.^[5] They most likely formed from the breakup of a basalt object, which in turn was spawned from a larger parent body that underwent igneous differentiation.^[6] The family's parent body and namesake is the asteroid 847 Agnia.^[5] In the 1995-HCM analysis by Zappalà, however, it is a member of the Liberatrix family (also described as Nemesis family by Nesvorný).^[3][7]

It orbits the Sun in the central main-belt at a distance of 2.5–3.0 AU once every 4 years and 7 months (1,674 days; semi-major axis of 2.76 AU). Its orbit has an eccentricity of 0.10 and an inclination of 4° with respect to the ecliptic.^[2] The body's observation arc begins with its observations as 1974 HY₁ at Cerro El Roble Observatory in April 1974, more than 6 years prior to its official discovery observation at Palomar.^[1]

Naming

This minor planet was named after New Zealand-born Australian amateur astronomer and rocket engineer William A. Bradfield (1927–2014). A discoverer of several comets himself, he significantly increased the rate of discovery of bright comets from the southern hemisphere during the 1970s and 1980s.^[1] The official naming citation was published by the Minor Planet Center on 14 April 1987 (M.P.C. 11750).^[8]

Physical characteristics

In the SMASS classification, Bradfield is an Sq-subtype, that transitions between the common, stony S-type and Q-type asteroids.^[2]

Diameter and albedo

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Bradfield measures 8.492 kilometers in diameter and its surface has an albedo of 0.269.^[4]

Rotation period

As of 2018, no rotational lightcurve of Bradfield has been obtained from photometric observations. The body's rotation period, pole and shape remain unknown.^[2]