90 Antiope
The most remarkable feature of Antiope is that it has two asteroids of almost equal size (the difference in mass is less than 2.5%), making it a truly "double" asteroid. Its binary nature was found on 10 August, 2000 by a group of astronomers using adaptive optics at the Keck Telescope on Mauna Kea. The "secondary" is designated S/2000 (90) 1.