NASA captured many detailed images of the large "pumpkin asteroid" that passed close by Earth on Halloween. The asteroid 2015 TB145 came within 1.3 lunar distances — or 300,000 miles — of our planet at around 1PM ET on October 31st. NASA bounced radar signals off the asteroid as it zoomed by at 22 miles per second; those signals helped create a thorough picture of the asteroid's surface. The highest-resolution images from the flyby have been processed and released today.
To create these radar photos, NASA used huge, Earth-based radio telescopes and antennas. First, a 230-foot antenna at Goldstone, California called DSS-14 sent microwaves at TB145, which then bounced off the space rock and headed back toward Earth. These signals were then received by the 100-meter Green Bank Telescope at the National Radio Astronomy Observatory in West Virginia. These signal reflections can be pieced together into images with resolutions of less than 13 feet per pixel. That's enough to show the various cavities, boulders, and ridges on the asteroid.
These are probably the only good pictures we'll have of TB145 for a while, too. The next time the asteroid is scheduled to stop by again is in September 2018. When it does, it will pass at a distance of 24 million miles, or a quarter of the distance between Earth and the Sun. Chances are we won't get nearly as good head shots for that flyby.
Verge Video: The Pumpkin asteroid, explained