Once Neptune was discovered, it took just seventeen days for William Lassell to find its moon Triton. None of its other 12 moons were found until the 20th century. Neptune is the fourth-largest planet in diameter and the third largest in terms of mass — 17 times that of Earth — in the solar system. It is also the farthest planet from the Sun since Pluto’s demotion in 2006.
The gas giant is often lumped together with Uranus under the label “ice giants” due to the fact that they are smaller and have a higher proportion of “ices” (such as water, ammonia and methane) then Jupiter and Saturn. Its atmosphere is composed primarily of hydrogen and helium and it’s pretty chilly, with temperatures approaching -218 degrees C. It’s also pretty windy, with gusts reaching speeds of up to 1,200 miles per hour.
So, although Neptune is a rather inhospitable place, we wish the planet a happy birthday. Link
(Image credit: NASA)