Deep-Sky Objects, Galaxies Two open clusters in Perseus, emission nebula NGC 1491, and barred spiral galaxy NGC 1512
Alien Life, Exoplanets, Planets, Robotic Spaceflight, Solar System MESSENGER provides first optical images of ice near Mercury’s north pole
Science I often read about a sunspot on the western limb of the Sun, or a crater on the eastern limb of the Moon, etc. As there is no “up” in space, how are north, south, east, and west determined?
