90 Antiope Facts for Kids

90 Antiope is a special space rock called an asteroid. It was first discovered on October 1, 1866, by a scientist named Robert Luther. It was the 90th asteroid ever found! Antiope is named after a character from Greek mythology, but scientists aren't sure if it's named after Antiope the Amazon warrior or Antiope, the mother of two heroes, Amphion and Zethus.

This asteroid travels in the outer part of the main asteroid belt, which is a big area between Mars and Jupiter where many asteroids orbit the Sun. Antiope is part of a group of asteroids known as the Themis family. Like many objects in this area, it looks dark because it's made of a material called carbonaceous chondrite, which is a type of rock that contains carbon.

Scientists have watched Antiope pass in front of stars (this is called an occultation) nine times since 1988. These observations help them learn more about the asteroid.

A Double Asteroid!

The most amazing thing about Antiope is that it's not just one asteroid, but two! These two asteroids are almost the same size, making it a true "double" asteroid. The difference in their weight is very small, less than 2.5%.

Scientists found out it was a double asteroid on August 10, 2000. They used a special telescope called the Keck Telescope in Hawaii, which has advanced technology to see very clearly in space. The second asteroid is officially called S/2000 (90) 1.

90 Antiope passed in front of the star LQ Aquarii on July 19, 2011. Many stations in the western USA observed this event.

Each of the two asteroids is about 86 kilometers (about 53 miles) wide. Their centers are only about 170 kilometers (about 105 miles) apart. This means the space between them is only about 60 kilometers (about 37 miles)!

The two asteroids orbit around a shared point in space, which is like their balance point. It takes them about 16.5 hours to complete one orbit around each other. Every few years, they pass in front of each other when viewed from Earth. By studying their orbit and size, scientists can figure out how heavy and dense these asteroids are.

Quick facts for kids
S/2000 (90) 1
Discovery
Discovered by	W. J. Merline, L. M. Close, J. C. Shelton, C. Dumas, F. Menard, C. R. Chapman, and D. C. Slater
Discovery date	August 10, 2000
Designations
Minor planet category	Main belt (Themis family)
Orbital characteristics
Semi-major axis	171 ± 1 km
Eccentricity	0.01 ± 0.02
Orbital period	0.687713 ± 0.00004 d (16.5051 ± 0.0001 h)
Average orbital speed	18.0 m/s
Satellite of	Binary with 90 Antiope
Physical characteristics
Dimensions	86±1 km
Mass	~ 8.1−8.5 ×10¹⁷ kg
Equatorial escape velocity	variable; ~ 35−40 m/s
Rotation period	0.687 d (16.50 h)
Absolute magnitude (H)	9.02