Asteroid 3015 Candy

3015 Candy is a main belt asteroid with an estimated diameter of about 15 km. It was discovered on November 9, 1980 by E. Bowell at Lowell Observatory. The semi-major axis is 3.395 AU, the eccentricity is 0.165 and the inclination is 17.425 degrees.

I first observed this asteroid on five nights during December 2005. The resulting lightcurve showed a period of about 4.6250 hours.

2005 lightcurve results for 3015 Candy. Derived period 4.6250 ± 0.001 hours. Amplitude 0.90 ± 0.01 magnitude.

Further observations were made on four nights during October and November 2011. This data resulted in a very good lightcurve with a period of about 4.6249 hours, confirming the 2005 result. More observations were obtained in 2014 and 2015.

2011 lightcurve results for 3015 Candy. Derived period 4.6249 ± 0.0001 hours. Amplitude 0.90 ± 0.01 magnitude.

2014 lightcurve results for 3015 Candy. Derived period 4.62516 ± 0.0001 hours. Amplitude 0.90 ± 0.01 magnitude.

2015 lightcurve results for 3015 Candy. Derived period 4.62538 ± 0.00004 hours. Amplitude 0.66 ± 0.01 magnitude.

The main reason for observing the asteroid the second time was to use the extra data to model the asteroid's shape.

The first step in the shape model analysis was to use the lightcurve data to derive a sidereal period, which was then applied in a pole search that generated a map of possible pole solutions. This is shown below.

Map of possible pole solutions for 3015 Candy. Dark blue indicates the lower values of log(chi-square) in the range of solutions. There is no strong solution as shown by the large area of blue. This indicates that the pole direction and therefore the shape are poorly constrained.

I was rather puzzled by this result until I looked more closely at the orbit. The orbital period is 6.25 years, almost exactly the interval between my observations! So I had observed the asteroid at the same solar longitude both times. This explained the lack of a definitive result. More observations at future oppositions are planned.