An infrared space telescope has spotted several very dark asteroids that have been lurking unseen near Earth's orbit. Their obscurity and tilted orbits have kept them hidden from surveys designed to detect things that might hit our planet.
Called the Wide-Field Infrared Survey Explorer (WISE), the new NASA telescope launched on 14 December on a mission to map the entire sky at infrared wavelengths. It began its survey in mid-January.
In its first six weeks of observations, it has discovered 16 previously unknown asteroids with orbits close to Earth's. Of these, 55 per cent reflect less than one-tenth of the sunlight that falls on them, which makes them difficult to spot with visible-light telescopes. One of these objects is as dark as fresh asphalt, reflecting less than 5 per cent of the light it receives.
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