No one bothered to formally name Triton until Neptune's second satellite, Nereid, was discovered in 1949, calling it simply "the satellite of Neptune." Named for the son of Poseidon, the Greek equivalent of Neptune, Triton resides 2.8 billion miles from the Sun. Its surface displays a peculiar netted or "cantelope" terrain and active cryovolcanoes. Covered in nitrogen frost and tholins (dark organic compounds that form when solar UV alters methane gas), Triton is one of the coldest places in the Solar System. Lassell ran a successful brewery business and used some of the money to build the telescope that revealed the first of the planet's 14 known moons. French mathematician Urbain Leverrier sent his predictions (based on irregularities in Uranus' motion) of the planet's location to German astronomer Johann Galle, who found it after only a half hour of looking on September 23, 1846.ġ7 days later on October 10, another amateur, William Lassell, nabbed Triton, following a suggestion made by astronomer John Herschel that a search for moons might prove fruitful. One could argue that beer was crucial to the discovery of Triton. Neptune is the only planet discovered by mathematical prediction rather than staring us in the face or through accidental telescopic discovery.
Click to download detailed charts for Neptune and Uranus. Neptune's position is shown for August 26, 2015. Once you've found it, use the detailed chart to spot Neptune in binoculars and telescopes. Your keystone star is Lambda Aquarii, circled in red. On nights of good seeing, when the disk focuses crisply, you can sense how remote the planet - nearly four times the size of our own - must be to look so minute. Is this how the Earth, suitably magnified, appears from Neptune, I wonder? The combination map shows the sky facing southeast in late August–early September around 10 o'clock local time from mid-northern latitudes. A 3-inch or larger telescope at 75x hints of its non-stellar nature, and if you increase the magnification to 150x or higher, a tiny blue disk emerges. Using only an inch-and-a-half telescope and 30x, he spotted the planet and recorded its position on two occasions, but apparently mistook it for a faint star.Īny pair of 7x binoculars mimics Galileo's view of Neptune, which looks like a slow-crawling "star" just west of the 4th magnitude Lambda Aquarii this season.
The two planets happened to be in close conjunction at the time, with Neptune in the same field of view. Galileo was the first to see Neptune on December 27, 1612, while observing Jupiter and its moons. Sometimes it's an obvious blue, other times a washed-out green or greenish-yellow. What do you see? I've found that Neptune's color varies depending on how long you stare at it and how tired your eyes are. The planet owes its remarkable blue hue to absorption of red light by methane in the atmosphere. Voyager 2, which flew by Neptune in August 1989, sent back photos of an aquamarine globe blemished by a huge, spinning storm called the Great Dark Spot. Methane in its atmosphere gives it a characteristic blue color. Neptune, the fourth largest planet, is nearly four times Earth's size.
Uranus follows suit the night of October 11. Neptune reaches opposition on August 31 when it will shine at magnitude +7.8 and present a tiny disk just 2.3″ across. Because both require optical aid, we often forget they're there. Two more planets have quietly joined the skyscape in recent weeks - Uranus and Neptune. I've gotten into the habit lately of thinking Saturn's the only remaining evening planet. Triton, like Pluto, is pink, but too faint to show color in amateur telescopes. Neptune and its largest moon Triton (1,700 miles in diameter) photographed on September 25, 2010. Neptune reaches opposition next week, giving amateurs the chance to track its unique, backwards-orbiting moon Triton.