Last weekend the asteroid 2014 HQ124 passed by our planet at just over three lunar distances — a safe distance, yes, but still a relatively close call for an object longer than an aircraft carrier and traveling a relative velocity of 31,000 mph! And even at that distance and speed astronomers were able to obtain some of the best images yet of any passing asteroid, by combining the power of radar telescopes located thousands of miles apart.
Before its June 8 close approach HQ124 had been nicknamed “The Beast” due to its considerable size. But now that the radar data has been obtained astronomers see it as anything but.
“These radar observations show that the asteroid is a beauty, not a beast,” said Alessondra Springmann, a data analyst at Arecibo Observatory, home of the 305-meter William E. Gordon Telescope.
With an elongated, lobed shape resembling a peanut, HQ124 is what’s known as a contact binary — a single large asteroid formed by the connection of two smaller ones.
By pairing the observation capabilities of NASA’s 70-meter DSS-14 antenna at Goldstone, California with those of the enormous 305-meter dish at Arecibo, and then later with a smaller 34-meter antenna in California, JPL astronomers were able to obtain some of the highest-resolution views ever of a near-Earth asteroid.
The collage above shows observations of HQ124 during its close approach, when it came within about 776,000 miles (1.25 million km) of Earth. Each frame represents 10 minutes of observation time, with the finest resolution being about 12 feet (3.75 meters). The first five images specifically are from the Goldstone-Arecibo partnership, and are brighter, more detailed, and contain less “snow.”
The surface structure of HQ124 can clearly be seen, with what seems to be a large depression on its larger lobe, some rocky outcrops at its far end, and a pointy hill rising up from its middle.
Watch an animation of the radar images below:
Other telescopes located in Texas, New Mexico, and Arizona were also used to pick up signals transmitted from Goldstone and Arecibo, providing robust measurements of the asteroid’s rotation rate.
“Using multiple telescopes to track the motion of an asteroid’s radar echo across the Earth, we can determine its rotation independently of radar imaging,” said Michael Busch, a radio astronomer involved with the observations at the SETI Institute. “This resolves ambiguities in the radar images and is essential for long-term trajectory prediction.”
With the success of this particular campaign astronomers plan to continue using the telescope team-up to image future close passes by asteroids.
Although designated a PHA — potentially hazardous asteroid — there was never any danger that HQ124 would impact Earth during this particular pass or any in the foreseeable future. (Its next close approach will be in November 2017 but then it will be considerably farther out.) Still, with 1,483 other known PHAs out there there’ll be no shortage of radar love for the Goldstone-Arecibo team.