The giant asteroid set to pass by Earth this week has a companion moon, according to NASA. The huge rock, which is 1.7 (2.7 kilometers) miles wide, will be closest to Earth on Friday at 4:59 p.m. EDT, but still far too distant to pose any danger to the planet, according to space agency officials.
NASA scientists discovered the moon orbiting asteroid 1998 QE2 yesterday evening (May 29) while obtaining a series of radar images with the 230-foot (70-meter) Deep Space Network antenna at Goldstone, California. The asteroid was about 3.7 million miles (6 million kilometers) away from Earth, or 15.6 lunar distances, at the time the moon was spotted. The radar observations were led by Marina Brozovic of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. Asteroid 1998 QE2 was first discovered on August 19, 1998, by astronomers at the Massachusetts Institute of Technology Lincoln Near Earth Asteroid Research (LINEAR) program near Socorro, New Mexico.
According to NASA, radar images indicate that the primary body is about 1.7 miles (2.7 kilometers) in diameter and has a rotation of about four hours. An initial estimate for the size of the asteroid’s satellite is approximately 2,000 feet (600 meters) wide. Radar imagery also showed several dark surface features suggesting large concave areas. Of all near-Earth asteroids that are 655 feet (200 meters) or larger, only about 16 percent are binary or triple systems.
At its closest point to Earth tomorrow, 1998 QE2 will be about 3.6 million miles (5.8 million kilometers) away–the nearest the asteroid will come to our planet for at least the next two centuries, say astronomers. Between May 30 and June 9, astronomers will use the Deep Space Network antenna in conjunction with the Arecibo Observatory in Puerto Rico to perform extensive observations of the asteroid. The two telescopes’s imaging capabilities complement each other, allowing astronomers to learn as much as possible about 1998 QE2 before it disappears from sight.
The asteroid flyby is the latest for Earth. Already a number of massive asteroid have passed Earth, missing us by millions of miles. At least one of them, the asteroid that exploded over the Russian town of Chelyabinsk, was undetected until it entered Earth’s atmosphere. Since then, scientists around the world have called for increased funding for asteroid detection programs.
Radar imaging is a powerful tool for studying an asteroid’s attributes, such as size, shape, rotation, surface features, and orbit. According to NASA, radar measurements of asteroid distances and speed can permit calculation of asteroid orbits much further into the future than without radar observations. However, with asteroid distances ranging from millions of miles from Earth to hundreds (or even billions) of miles from Earth, it is difficult to tell exactly how many are large enough to support their own moons. Some experts have estimated that upwards of five to ten percent of asteroids are large enough to support their own moons.
NASA plays a crucial role in tracking asteroids and protecting Earth’s inhabitants from them. Of all the countries in the world, the United States has the most robust near-Earth asteroid detection programs, discovering more than 98 percent of all known near-Earth objects to date, according to the space agency. Still, speaking before U.S. lawmakers earlier this year, experts have warned that the ability to detect even fairly large asteroids is far from perfect. A number of astronomers have warned that even a medium-sized asteroid could cause significant destruction should it strike one of Earth’s larger cities.
NASA plans to launch a robotic probe in 2016 to one of the most potentially dangerous Near-Earth Objects, asteroid 101955 Bennu. The OSIRIS-REx mission will pave the way for future spacecraft to perform reconnaissance on any newly-found space objects that could pose a threat to Earth.