M, Rizzi M, Gadaleta F, Grechi A, Baiardini R, Fanfulla F, et al.
0 denotes no asteroids, 4 as perturbers are asteroids: (1) Ceres, (2) Pallas, (4) Vesta, and (10) Hygiea, additions for 16 asteroids: (3) Juno, (6) Hebe, (7) Iris, (15) Eunomia, (16) Psyche, (29) Amphitrite, (52) Europa, (65) Cybele, (88) Thisbe, (511) Davida, and (704) Interamnia, and additions for 25 asteroids: (11) Parthenope, (14) Irene, (56) Melete, (63) Ausonia, (135) Hertha, (259) Aletheia, (324) Bamberga
, (419) Aurelia, and (532) Herculina (see Table 6 in Chesley et al.
Asteroid 324 Bamberga
reaches opposition near the Circlet of Pisces on September 13th, when it's just 0.81 a.u.
The main-belt asteroid 324 Bamberga has a very ordinary orbital period of 4.395 years, but its unusually high orbital eccentricity (0.34) brings it closer to Earth than any other asteroid so large ever comes.
Bamberga is magnitude 9.5 on August 1st, 8.4 by September 1st, 8.1 at opposition on September 13th, 8.5 October 1st, and 9.3 November 1st.
Although it was discovered much earlier and hence is much lower-numbered than Bamberga, 7 Iris is similarly bright around its opposition this summer.
Iris is the same size as Bamberga but has a much more reflective surface (albedo 28%), and this makes up for its being farther away.
About 25 years ago, the asteroid 324 Bamberga
caught the attention of researchers seeking the origin of carbonaceous meteorites because it was found to have an albedo (reflectivity) of only 6 percent.