An asteroid passed Earth last week, and with the Arecibo radio telescope astronomers got an unprecedented look—along with a couple surprises.
Asteroid 1998 QE2 came within six million kilometers of Earth, about 15 times the distance to the Moon. Researchers used Arecibo’s 300-meter-wide dish to bounce radio signals off the rock. By measuring how quickly the transmitted signals returned, the researchers could map the asteroid’s surface.
The first images, however, came back with a twist: the asteroid has a moon. At one quarter the size of the three-kilometer-diameter asteroid, the moonlet has the same proportional size to 1998 QE2 as our moon does to Earth. The discovery is a pleasant bonus: astronomers can calculate the asteroid’s mass by measuring how quickly the satellite orbits it.
Spectra obtained at NASA’s Infrared Telescope Facility in Hawaii also revealed that the asteroid’s surface has not been significantly altered from its original composition. That makes 1998 QE2 unique among all known asteroids and collected meteorites. So-called “primitive” asteroids can reveal details about the origin and evolution of the solar system.
via Arecibo Telescope Gets Detailed Look at Passing Asteroid: Scientific American Gallery.
