2021 SG passed us safely on Sept. 16, but at a relatively close distance -- astronomically speaking -- of around 153,000 miles (246,000 km). If it had entered Earth's atmosphere, it likely would have caused destruction, especially if it hit near a populated area. The Chelyabinsk meteor and asteroid 2021 SG point out a literal blind spot when it comes to watching for so-called near-Earth objects: the sun. As NASA solar system ambassador Eddie Irizarry and EarthSky editor-in-chief Deborah Byrd explain, both space rocks went undetected as they approached us because they came from the direction of the sun. NASA...