On July 25, the asteroid made its closest approach to Earth at a distance of about 7.2 million km or about 19 times the distance from Earth to the moon.
"Radar imaging has shown that about 15 percent of near-Earth asteroids larger than 600 feet [about 180 meters], including 1999 JD6, have this sort of lobed, peanut shape," said Lance Benner of NASA's Jet Propulsion Laboratory in Pasadena, California.
To obtain the views, researchers paired NASA's Deep Space Network antenna at Goldstone, California with the National Science Foundation Green Bank Telescope in West Virginia.
Using this approach, the Goldstone antenna beams a radar signal at an asteroid and Green Bank receives the reflections. The technique, referred to as a bistatic observation, dramatically improves the amount of detail that can be seen in radar images.
The images show the asteroid is highly elongated, with a length of approximately 2 km on its long axis.
This flyby was the closest approach the asteroid will make to Earth for about the next 40 years. The next time it will approach Earth this closely is in 2054, at approximately the same distance of this flyby.