Neptune

Credit: NASA

Neptune is the eighth planet from the Sun making it the most distant in the solar system. This gas giant planet may have formed much closer to the Sun in early solar system history before migrating to its present position.

Equatorial Diameter: 49,528 km

Polar Diameter: 48,682 km

Moons: 14 (Triton)

Rings:5Orbit Distance: 4,498,396,441 km (30.10 AU)

Orbit Period: 60,190 days (164.8 years)

Effective Temperature: -214 °C

Discovery Date: September 23rd 1846

Discovered By: Urbain Le Verrier & Johann Galle

Neptune was not known to the ancients. It is not visible to the naked eye and was first observed in 1846. Its position was determined using mathematical predictions. It was named after the Roman god of the sea. Neptune is the smallest of the ice giants. Despite being smaller than Uranus, Neptune has a greater mass. Below its heavy atmosphere, Uranus is made of layers of hydrogen, helium, and methane gases. They enclose a layer of water, ammonia and methane ice. The inner core of the planet is made of rock.The atmosphere of Neptune is made of hydrogen and helium, with some methane. The methane absorbs red light, which makes the planet appear a lovely blue. High, thin clouds drift in the upper atmosphere. Neptune spins on its axis very rapidly. Its equatorial clouds take 18 hours to make one rotation. This is because Neptune is not solid body.

Neptune has 14 moons. The most interesting moon is Triton, a frozen world that is spewing nitrogen ice and dust particles out from below its surface. It was likely captured by the gravitational pull of Neptune. It is probably the coldest world in the solar system.

Neptune has an incredibly thick atmosphere comprised of 74% hydrogen, 25% helium and approximately 1% methane. Its atmosphere also contains icy clouds and the fastest winds recorded in the solar system. Particles of icy methane and minor gases in the extremities of the atmosphere give Neptune its deep blue colour. The striking blue and white features of Neptune also help to distinguish it from Uranus.

Significant Dates:

• 1846: Using mathematical calculations, astronomers discover Neptune, increasing the number of known planets to eight. Neptune's largest moon, Triton, is found the same year.
• 1984: Astronomers find evidence for the existence of a ring system around Neptune.
• 1989: Voyager 2 becomes the first and only spacecraft to visit Neptune, passing about 4,800 km (2,983 miles) above the planet's north pole.
• 1998: Scientists using telescopes on Earth and in space image Neptune's rings and ring arcs for the first time.
• 2003: Using improved observing techniques, astronomers discover five new moons orbiting Neptune.
• 2005: Scientists using the Keck Observatory image the outer rings and find that some of the ring arcs have deteriorated.
• 2011: Neptune completes its first 165-year orbit of the sun since its discovery in 1846.
• 2013: A scientist studying Neptune's ring arcs in archival Hubble Space Telescope images finds a previously unknown 14th moon of Neptune, provisionally designated S/2004 N 1.

Credit: Karl Tate/Space.com

Reference: Karl Tate/spacedotcom/Nasa Solar System