Spooky may be a rough character, but scary? Naw. The usual lumps and bumps, but given its small size, maybe more spherical than expected. On Halloween morning, the near-Earth asteroid 2015 TB145 (nicknamed ‘Spooky’) flew only 300,000 miles (486,000 km) from Earth and became bright enough to see in a modest-sized telescope. It was also the focus of a radar-imaging campaign involving three large radio telescopes.
NASA scientists used used the scopes to bounce radar signals off the asteroid as it flew past Earth. The returned echoes paint a picture of a spherical body 1,968 feet (600 meters) in diameter.
Animation using new radar images of asteroid 2015 TB145 from Arecibo Observatory in Puerto Rico November 1, 2015. The video clearly shows boulders littering the surface.
“The radar images of asteroid 2015 TB145 show portions of the surface not seen previously and reveal pronounced concavities, bright spots that might be boulders, and other complex features that could be ridges,” said Lance Benner of NASA’s Jet Propulsion Laboratory, who leads NASA’s asteroid radar research program. “The images look distinctly different from the Arecibo radar images obtained on Oct. 30 and are probably the result of seeing the asteroid from a different perspective in its three-hour rotation period.”
To obtain the radar images, the scientists used the 230-foot (70-meter) DSS-14 antenna at Goldstone, California, to transmit high power microwaves toward the asteroid. The signal bounced of the asteroid, and their radar echoes were received by the National Radio Astronomy Observatory’s 100-meter (330-foot) Green Bank Telescope in West Virginia. The images achieve a spatial resolution of about 13 feet (4 meters) per pixel.
Asteroid 2015 TB145 was discovered in October by the Pan-STARRS I survey in Hawaii and classified as a potentially hazardous asteroid due to its size and relative proximity to Earth. Its next pass will be in September 2018 when it will miss us by 24 million miles (38 million km).
The asteroid reflects only 6% of the light it receives from the sun, making it similar in brightness to fresh asphalt here on Earth. Dark for sure but still twice as bright as a typical comet nucleus. One of our readers, Richard Keen of Colorado, spotted it easily in his telescope and thought he saw changes in its brightness that may have been an indication of rotation.
Nice that it dropped by, so we could get acquainted. That’s the closest TB145 will come to Earth for the remainder of the century.