Why is Neptune Blue?
Neptune is the eighth planet, and now the farthest, since Pluto is no longer a planet, from our in our solar system, with a bright azure blue color. Any time we see a planet, it is because of the reflection of the sun’s light off the planet’s atmosphere; this is also the reason that the moon appears illuminated on some nights, and not on other nights ‘š it isn’t emitting light, but merely reflecting the light from the sun back onto the earth. The changes in size and ‘shape’ of the moon, from full moon, to a half moon, to a crescent moon, and finally a new moon are actually shadows of the earth being cast onto the moon from the angle that the moon-earth-sun triad is making.
Neptune, however, does not have shadows cast by the earth upon its surface; it is much too far away. But it can still be seen at night through telescopes and other instruments (though not with the naked eye, it is too far away). When early astronomers saw the beautiful cerulean-esque planet, they thought of a world of picturesque oceans, and subsequently named it after the Roman god Neptune. In Greece, this god’s name was Poseidon. He was the lord of all the oceans in both mythologies (the Romans effectively stole the Greek mythology) and brother to both Zeus and Hades in Greek mythology, and Jupiter and Pluto to the Romans.
The azure blue of Neptune comes directly from the reflection of the sun off of its atmosphere ‘š because it is such a gaseous planet, the surface itself is not seen. The surface is not much more interesting than ice and rocks. However, it is the gas that contains the secret to the color. Similar to Jupiter and Saturn, it contains primarily hydrogen and helium,¦ but it also contains higher proportions of water, ammonia and methane. It is this last chemical, methane, which absorbs the red and longer end of the visible spectrum of light, reflecting back Neptune’s characteristic blue.