Neptune involves opposition at late-evening on Friday, 16 September, when it’s situated among the many stars of northern Aquarius. The farthest recognized planet lurks within the frigid depths of the Photo voltaic System, mendacity on the huge distance of 4.324 billion kilometres (28.910 astronomical models) from Earth – daylight mirrored from Neptune takes 4 hours to hit our retinas! But Neptune shines shiny sufficient, at magnitude +7.8, to be picked up in a pair of binoculars and is a simple goal for a small telescope. Not surprisingly, given the planet’s enormous remoteness, Neptune is properly past naked-eye vary, the one planet the Photo voltaic System that’s.
On opposition night time, Neptune will be tracked right down to a reasonably star-poor space of north-eastern Aquarius, near the boundary with Pisces. At this location, only a few levels south of the celestial equator, the ice-giant planet culminates round 35° excessive from the south of England at about 1am BST. Neptune stays on present within the night to early night sky for the remainder of the 12 months.
Observers based mostly at mid-northern latitudes have had a really lengthy anticipate Neptune to realize an honest peak altitude. Certainly, not for the reason that late Forties has Neptune appeared as far north within the sky. It lingered lengthy within the depths of the southern sky for many of the later half of the twentieth-century.
Neptune is a gaseous ice-giant planet with a radius of 24,764 kilometres (15,388 miles), 4 occasions wider than Earth although 3 times smaller than Jupiter. It lies so distant that each one amateurs can see by a telescope is its tiny, 2.4”-sized disc. A telescope within the 100–150mm (four- to six-inch) class, working at round 100x, is highly effective sufficient to resolve Neptune’s tiny blue-green disc. Sadly, even a big telescope struggles to glean a lot element on its reasonably bland disc, although excessive decision planetary imagers ought to have extra success, particularly when utilizing infra-red filters in conjunction with an infra-red delicate digicam.
Neptune does boast a large moon known as Triton; in Greek mythology a god of the ocean and the son of Poseidon and Amphitrite. Triton is 2,710 kilometres (1,680 miles) in diameter, rating it the seventh-largest moon within the Photo voltaic System. It shines at magnitude +13.4, shiny sufficient to be discovered by a 250–300mm (10- to 12-inch) telescope.
Triton completes an orbit of Neptune in 5.9 days, and from our perspective its distinctive retrograde movement alongside an elliptical path takes it as distant as 17 arcseconds from Neptune.
