New observations by three of the world's largest radio telescopes (including the Arecibo Observatory) have revealed that an asteroid discovered last year is actually two objects, each about 3,000 feet (900 meters) in size, orbiting each other. Read More

NASA-funded Arecibo Planetary Radar system was tested for the first time since hurricane Maria with a successful detection of near-Earth asteroid 2007 AG. This object at its closest approach to Earth will be some 0.059 AU and is estimated to be 300 meters in diameter

Columbia, MD and Puerto Rico — December 22, 2017. After several months of downtime since Hurricane Maria struck the island of Puerto Rico, the Arecibo Observatory Planetary Radar has returned to normal operation, providing the highest-resolution images to date of near-Earth asteroid 3200 Phaethon during its December 2017 close approach to Earth. The radar images, which are subtle at the available resolution, reveal the asteroid is spheroidal (roughly ball-shaped) and has a large concavity, or depression, at least several hundred meters in extent near its equator, and a conspicuous dark, circular feature near one of the poles. Arecibo’s radar images of Phaethon have resolutions as fine as about 250 feet (75 meters) per pixel. Read More

M-class asteroids are a relatively rare type of asteroid in the main asteroid belt, located between the orbits of Mars and Jupiter. For many years, planetary scientists have thought that they were the remnants of small protoplanets that were shattered in the violent early days of the solar system, leaving only an exposed metal core behind. Unfortunately, determining whether an asteroid is mostly metallic is very difficult with traditional optical telescopes. For the past decade, we have used the Arecibo Planetary Radar to probe these objects, for only a radar telescope can give an unambiguous indication of a metallic composition. Read More