Duck! NASA just released a second year’s worth of survey data taken by its NEOWISE space telescope and it shows 439 NEOs categorized since 2013 with 72 being new discoveries and 8 that are potentially hazardous asteroids (PHAs). Duck!
Duck? Why? What’s NEOWISE? This spacecraft was launched in December 2009 as the Wide-field Infrared Survey Explorer (WISE). Its original mission was to create infrared images of 99 percent of the sky, using four wavelengths of the infrared band and taking at least eight images of each position for accuracy. That massive undertaking was completed successfully by October 2010 (over 33,500 new asteroids and comets were discovered and nearly 154,000 Solar System objects were observed) and WISE was put into hibernation in February 2011.
Yeah, yeah ... what about the eight hazardous asteroids? We’re getting to them. WISE was reactivated in 2013 as Near-Earth Object Wide-field Survey Explorer (NEOWISE) with a new mission to discover, size and track both new and previously known potentially hazardous near-Earth objects. In the past year, NEOWISE’s 16-inch (40-cm) telescope and infrared cameras captured about 5.1 million images and processed information on more than 19,000 asteroids and comets. JPL’s Amy Mainzer, NEOWISE’s principal investigator, describes them.
NEOWISE discovers large, dark, near-Earth objects, complementing our network of ground-based telescopes operating at visible-light wavelengths. On average, these objects are many hundreds of meters across.
Hundreds of meters across? Duck! Run! Duck and run! NASA defines “Potentially Hazardous Asteroids (PHAs) as “all asteroids with an Earth Minimum Orbit Intersection Distance (MOID) of 0.05 AU or less and an absolute magnitude (H) of 22.0 or less are considered PHAs.” That means asteroids that can come within 7,480,000 km or 4,650,000 mi of Earth and are at least 150 m (500 ft) in diameter.
Where are they? Duck! That’s NASA’s secret. If you look at the map it released, they’re part of the green dots representing NEOs (Earth's orbit is the green circle, the yellow squares are comets and the grey dots are all other asteroids.
That looks bad. Actually, it’s good. At least we know where these are. As the meteor explosion over the South Atlantic in February 2016 indicated, it’s not the ones we know about that should worry us … it’s the ones that sneak up unexpectedly.
Are you talking about potentially hazardous asteroids or flatulence? Both. Hold your nose and duck!