|Discovered by||Johann Palisa|
|Discovery date||February 25, 1892|
|Minor planet category||Main belt|
|Epoch 30 January 2005 (JD 2453400.5)|
|Aphelion||537.241 Gm (3.591 AU)|
|Perihelion||265.576 Gm (1.775 AU)|
|Semi-major axis||401.409 Gm (2.683 AU)|
|Orbital period||1605.397 d (4.4 a)|
|Average orbital speed||18.18 km/s|
|Longitude of ascending node||328.058°|
|Argument of perihelion||44.062°|
|Dimensions||234.67 ± 7.80 km
229.4 ± 7.4 km (IRAS)
(1.03 ± 0.10) × 1019 kg
|Mean density||1.52 ± 0.20 g/cm3|
|Equatorial surface gravity||0.055 m/s²|
|Escape velocity||0.11 km/s|
|Rotation period||1.226 d
|Spectral type||C-type asteroid|
|Absolute magnitude (H)||6.82|
324 Bamberga is one of the largest asteroids in the asteroid belt. It was discovered by Johann Palisa on February 25, 1892 in Vienna, making it one of the last large (diameter over 200 km) asteroids discovered. Apart from the near-earth asteroid Eros, it was the last asteroid which is ever easily visible with binoculars to be discovered.
Although its very high orbital eccentricity means its opposition magnitude varies greatly, at a rare opposition near perihelion Bamberga can reach a magnitude of +8.0, which is as bright as Saturn's moon Titan. Such near-perihelion oppositions occur on a regular cycle every twenty-two years, with the last occurring in 1991 and the next in 2013, when attaining magnitude 8.1 on September 13. Its brightness at these rare near-perihelion oppositions makes Bamberga the brightest C-type asteroid, roughly one magnitude brighter than 10 Hygiea's maximum brightness of around +9.1. At such an opposition Bamberga can in fact be closer to Earth than any main-belt asteroid with magnitude above +9.5, getting as close as 0.78 AU. For comparison, 7 Iris never comes closer than 0.85 AU and 4 Vesta never closer than 1.13 AU (when it becomes visible to the naked eye in a light pollution-free sky).
Overall Bamberga is the tenth brightest main-belt asteroid after, in order, Vesta, Pallas, Ceres, Iris, Hebe, Juno, Melpomene, Eunomia and Flora. Its high eccentricity (for comparison 36% higher than that of Pluto), though, means that at most oppositions other asteroids reach higher magnitudes.
10µ radiometric data collected from Kitt Peak in 1975 gave a diameter estimate of 255 km. An occultation of Bamberga was observed on 8 December 1987, and gave a diameter of about 228 km, in agreement with IRAS results. In 1988 a search for satellites or dust orbiting this asteroid was performed using the UH88 telescope at the Mauna Kea Observatories, but the effort came up empty.
- See Asteroids in fiction.
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