Category Archives: Asteroids
The dwarf planet Ceres, at 587 miles wide the largest object in the main asteroid belt between Mars and Jupiter, has a different surface composition than previously thought—and it took NASA and DLR’s Boeing 747-based SOFIA observatory to make the distinction. By observing Ceres in mid-infrared, only possible from high altitudes above infrared-absorbing water vapor, SOFIA found that Ceres is covered in silicates—pyroxenes—that likely came from impacts, the result of infalling material from elsewhere in the asteroid belt…the “dust” of asteroid collisions.
Astronomers are always watching the skies for observations of near-Earth asteroids—”space rocks” that have orbits close to Earth’s and, in the case of potentially hazardous asteroids (aka PHAs), those whose orbits could actually cross Earth’s and are larger than 150 meters (500 ft) across. When a new one of these is discovered—no small feat considering that many are very dark, move quickly, and could really be anywhere in the sky—it’s a scramble to determine the object’s orbital parameters and figure out just how close it can get to us and when. Such was the case on Oct. 19, 2016, when the asteroid 2016 WJ1 was identified with the Catalina Sky Survey. This object, estimated to be anywhere from 110 to 340 meters across—easily within the potentially hazardous range—was initially calculated to pose a threat in 2065 with a possible impact risk, albeit a very small one. Eventually though, scientists were able to refine the risk chance with more observations of 2016 WJ1…observations that had actually occurred over 13 years earlier.
Read the full story from ESA here: Asteroid sleuths go back to the future
This week NASA’s Jet Propulsion Laboratory announced news of an object traveling around the Sun in an orbit that keeps it relatively close to our own planet. The object, a near-Earth asteroid (NEO) less than 300 feet (100 m) across, is designated 2016 HO3 and has in some reports been called a “new” or “mini” moon of Earth…but that’s not entirely true. More accurately 2016 HO3 is what’s known as a quasi-satellite, and is in a temporary (albeit long-lived by human standards) orbit that takes it on a “leapfrog” path around Earth, never getting closer than 38 times the distance to the Moon—about 9.1 million miles.
After more than a dozen years of head-scratching we finally have our first really good look at the weird bright spot on Ceres, thanks to NASA’s Dawn spacecraft and its low-altitude mapping orbit (aka LAMO) around the dwarf planet. Appearing from 240 miles up as a dome covered in cracks and rising from the surrounding darker terrain, the largest of Ceres’ bright spots looks not unlike… a giant pimple.
Researchers using the High Accuracy Radial velocity Planet Searcher (HARPS) instrument on ESO’s 3.6-meter telescope at La Silla have detected “unexpected” changes in the brightness of Ceres during observations made in July and August of 2015. Variations in line with Ceres’ 9-hour rotational period were expected, but other fluctuations in brightness were also found that indicate albedo changes on a daily, diurnal basis.
Long story short: Ceres is slowly “blinking.”