Astronomy Journal Entry
Hubble Looks at Outer Planets (February 14, 2004)
New color-enhanced views of Uranus and Neptune. Courtesy Hubble Space Telescope.
NASA recently released new Hubble Space Telescope views of Uranus and Neptune. The color-enhanced photos reveal details of the atmospheres of both of the gas giants.
The view of Uranus at lower left shows details of the planet's faint rings (color bands) and several of its moons (red dots). The planet has eleven known rings. They are dark like Jupiter's rings and made up of large particles (up to ten meters in diameter) and fine dust like Saturn's.
The blue color of Uranus is due to the absorption of red light by methane gas in its atmosphere. Methane makes up about 2% of the planet's atmosphere. The rest is made up of hydrogen (83%) and helium (15%).
Neptune's atmosphere is similar to that of Uranus. It is mostly hydrogen and helium with small amounts of methane. As with Uranus, the planet's methane absorbs the red wavelengths of the spectrum, making the planet appear blue. Neptune also has four faint, dark rings but scientists know very little about what they are made of.
Neptune has 13 known moons. Triton, discovered in 1846, is by far the largest (830 miles or 1,350 kilometers in diameter) and best known. By contrast, Uranus has at least twenty-seven moons although most are very small. The largest is Titania, which measures about 490 miles (790 kilometers) across.
