镶蓝带的红月
2021年12月01日 A Blue-Banded Blood Moon Image Credit: Angel Yu Explanation: What causes a blue band to cross the Moon during a lunar eclipse? The blue band is real but usually quite hard to see. The featured HDR image of last week’s lunar eclipse, however — taken from Yancheng, China — has been digitally processed to equalize the Moon’s brightness and exaggerate the colors. The gray color of the bottom right is the Moon’s natural color, directly illuminated by sunlight. The upper left part of the Moon is not directly lit by the Sun since it is being eclipsed — it in the Earth’s shadow. It is faintly lit, though, by sunlight that has passed deep through Earth’s atmosphere. This part of the Moon is red…