Pallas

Pallas is the second-largest asteroid in the solar system with a diameter of 544 km, orbiting at 2.77 AU in the asteroid belt. Despite its size, Pallas is far less well understood than Vesta or Ceres because its highly inclined orbit (34.8°) makes it difficult for spacecraft to reach. Pallas has an irregular, somewhat elongated shape and a relatively dark surface (albedo 0.16) composed of carbonaceous material similar to CM chondrite meteorites. Its surface appears heavily cratered and possibly contains hydrated silicate minerals, suggesting it has retained some water-bearing compounds since the early solar system. Pallas accounts for about 7% of the total mass of the asteroid belt.

At favorable oppositions, Pallas reaches about magnitude 6.7 — visible in binoculars but not to the naked eye. It typically appears between magnitude 7 and 9, requiring binoculars or a small telescope. Its highly inclined orbit means Pallas can appear far from the ecliptic, sometimes wandering into northern constellations like Ursa Major or southern ones well below the zodiac. This unusual sky position can actually help with identification, as few asteroids travel so far from the ecliptic plane. Track its nightly motion against background stars over two to three nights to confirm identity. Oppositions occur roughly every 16 months.

Pallas was discovered on March 28, 1802 by Heinrich Olbers while he was searching for Ceres, which had been found the previous year. It was the second asteroid ever discovered and was initially considered a planet. The name honors Pallas Athena, the Greek goddess of wisdom. Its discovery was pivotal in establishing that a new class of small bodies existed between Mars and Jupiter. No spacecraft has ever visited Pallas, largely because its extreme orbital inclination would require enormous fuel to match — making it the largest unexplored object in the inner solar system.