Asteroid 180 Garumna

Asteroid 180 Garumna is a main belt asteroid that was discovered by the French astronomer Henri Joseph Perrotin on January 29, 1878. The semi-major axis is 2.72AU and the eccentricity is 0.169 with a very low inclination of 0.87 degrees.

I first observed this asteroid in 2004. My initial results indicated a rotation period of almost exactly 24 hours, which meant that international colaberation was required to observe the full lightcurve. After putting out a request for other observers to assist, R. Roy, D. Starkey, and S. Sposetti contributed and our combined data enabled R. Behrend to derive a provisional rotation period of 23.85 h.

2004 lightcurve results for Asteroid 180 Garumna.
The derived period was 23.85 hours with an amplitude of about 0.5 magnitude. Image courtisty R. Behrend.

I obtained further observations of the asteroid in 2009 while it was in the field of the asteroid I was principally studying. These observations supported a period somewhat over 23 hours. However, since the observations only covered a small portion of the lightcurve, the period could still only be consideredapproximate.

2009 lightcurve results for Asteroid 180 Garumna.
The derived period was 23.32 hours with an amplitude of about 0.6 magnitude.

Finally in 2011, Frederick Pilcher lead an international collaboration which successfully observed the complete lightcurve of the asteroid and derived a period of 23.866 hours and an amplitude of about 0.45 magnitude.