Astraea

Astraea (5 Astraea) is a large main-belt asteroid with a diameter of about 119 km, orbiting the Sun at 2.58 AU. It is an S-type asteroid with a moderately reflective, stony surface composed primarily of silicates and nickel-iron. Astraea holds a unique place in asteroid discovery history: it was the fifth asteroid found, but only after a 38-year gap since the discovery of Vesta in 1807. Its discovery reignited the search for minor planets and opened the floodgates — within a decade, dozens more asteroids had been found. Astraea orbits in the inner to middle region of the asteroid belt with a relatively low inclination of 5.4°.

At opposition, Astraea reaches about magnitude 9.0 to 9.5, requiring a small telescope to observe. Its brightness ranges from magnitude 9 to 12 depending on its orbital position, making it a moderately challenging target. Best viewed around opposition, which occurs roughly every 15 months. Astraea's relatively slow motion against the background stars (given its mid-belt position) means you can confirm it by observing its displacement over two or three nights. Use a detailed star chart or planetarium software to identify the correct star field, and compare your view on consecutive nights to spot the asteroid's motion.

Astraea was discovered on December 8, 1845 by Karl Ludwig Hencke, a German amateur astronomer and postal worker from Driesen (now Drezdenko, Poland). Hencke had spent 15 years systematically searching for new asteroids after being inspired by the earlier discoveries of Ceres, Pallas, Juno, and Vesta. His persistence paid off spectacularly, breaking a 38-year discovery drought. The King of Prussia awarded Hencke an annual pension for his achievement. The asteroid was named after Astraea, the Greek goddess of justice and innocence, who was the last of the immortals to live among humans during the Golden Age before ascending to become the constellation Virgo.