Iris

Iris is a bright S-type asteroid with a diameter of about 200 km, orbiting at 2.39 AU in the inner asteroid belt. It has one of the highest albedos among main-belt asteroids (0.28), giving it a reflective surface composed of a mixture of nickel-iron metals and magnesium- and iron-silicates. Iris is thought to be a remnant planetesimal from the early solar system — a largely intact body rather than a collisional fragment. Unlike most large asteroids, Iris does not have an associated collisional family, suggesting it has survived the age of the solar system without being catastrophically disrupted. Iris may be a significant source of L and LL chondrite meteorites that fall on Earth.

Iris is one of the brightest asteroids, reaching magnitude 6.7 at favorable oppositions — easily visible in binoculars. At typical oppositions it ranges between magnitude 7 and 9, well within reach of a small telescope. Its position in the inner asteroid belt means it moves relatively quickly against the background stars, making motion detection over consecutive nights straightforward. The best viewing months are typically around August through October when oppositions often occur. Use a detailed ephemeris or planetarium software to plot its position and identify it among surrounding stars.

Iris was discovered on August 13, 1847 by English astronomer John Russell Hind at the George Bishop Observatory in London. It was the seventh asteroid discovered and was named after Iris, the Greek goddess of the rainbow and messenger of the gods. Hind was a prolific asteroid hunter who would go on to discover ten asteroids in total. No spacecraft has visited Iris, but extensive ground-based studies including radar observations and lightcurve analysis have revealed its approximate shape, rotation period, and surface composition.