Pin Me

The Scientific Reason Behind Neptune’s Blue Color

written by: Anurag Ghosh•edited by: George Adcock•updated: 3/9/2010

Neptune’s alluring bright azure color has always been associated with spirituality and the occult. But, why is Neptune Blue? Is there any scientific reason behind its color? Let’s find out…

  • slide 1 of 3

    Neptune: The Bright Azure Planet

    Why is Neptune Blue in Color? Neptune’s vibrant blue color looks spectacular when observed with a powerful telescope. With a mass of 1.02 x 1026 kg, it is 17 times heavier than Earth. Around 11 known satellites orbit Neptune, but the planet’s largest moon Triton has a retrograde orbit, i.e. it orbits in a direction opposite to Neptune’s rotation. Named after the Roman god of sea, Neptune’s enticing bluish hue is associated with mysticism, spirituality and imagination in astrology. But why is Neptune blue? What’s the exact reason behind Neptune’s bright bluish color?

  • slide 2 of 3

    The Reason Why Neptune is Blue in Color

    Before we delve deep into the key reasons behind the planet’s bright blue color, let us first discuss its surface and atmosphere:

    Neptune is chiefly made up of gases and is mainly composed of liquid ammonia, hydrogen, helium, methane. Neptune is one of the four major gas giants of the solar system; the other three are Uranus, Jupiter and Saturn. Neptune’s surface is covered by thick clouds unlike Earth’s solid surface. Its interior is composed of heavily compressed gases, which combine into a layer of liquid and surround its rocky core.

    Neptune’s bright azure blue was first revealed by NASA’s Voyager 2 during its flyby in 1989. The exact color revealed was completely distinct from Uranus’s pale blue color. So, why is Neptune blue in color?

    As previously discussed, Neptune is mainly composed of gases like hydrogen and helium. Its atmosphere comprises one percent methane, 19 percent helium and around 80 percent hydrogen. The main reason behind Neptune’s blue color is methane. When sunlight hits the planet’s surface, the methane clouds absorbs the red end of the spectrum of visible light. The blue end of the spectrum gets reflected back. So, when we see the bright bluish color of Neptune, we actually see the reflected sunlight, minus the red light.

    Neptune looks like a beautiful blue sphere from a distance, but the color variations in its clouds can be clearly noticed, if viewed closely. The surface of Neptune is also well-known for powerful storms. During the 1989 flyby, NASA’s Voyager 2 spacecraft noticed a dark area composed of gases. The area, made up of swirling gases, looked like a hurricane and was similar to the Great Red Spot on Jupiter. The dark area was later called the Great Dark Spot, but in 1994 the Hubble Space Telescope was not able to locate the dark area as it had completely vanished in thin air.

    If you search the Internet, you will find several fascinating facts about Neptune. While some facts explain about the planet’s vital stats, other shed light on the latest findings, mysteries and controversies surrounding its discovery. However few have discussed why Neptune is blue in color. Hope this article will help you understand why Neptune is blue and what its scientific reason is. You can also find out why Mars appears reddish in Bright Hub’s in-depth article about Mars’s reddish-orange appearance.

  • slide 3 of 3

    References

    Smith, Bradford A. "Neptune." World Book Online Reference Center. 2004. World Book, Inc. http://www.nasa.gov/worldbook/neptune_worldbook.html

    http://www.universetoday.com/guide-to-space/neptune/color-of-neptune/

    http://www.universetoday.com/guide-to-space/neptune/

    Image Reference:

    Photograph of Neptune, courtesy NASA (http://photojournal.jpl.nasa.gov/catalog/PIA00046)