Tonight – December 6, 2016 – don’t expect to see Neptune with the eye alone. It’ll be tough to see even with optical aid because it’s near the moon on December 6. In fact, the moon will cover or occult Neptune on this date, sailing peacefully in front of it and blotting it temporarily from view. The occultation of Neptune will be visible, weather permitting, over a swath of the Western Hemisphere including the northeastern USA, eastern Canada, Greenland, Iceland and the western British Isles. AstronomyNow said:
As seen from Reykjavik in Iceland, Neptune starts to disappear at 22:14:33 GMT, the planet’s 2.3-arcsecond-wide disc taking about 4 seconds of time to be fully occulted. Neptune lies just 9 degrees high in the southwest at the time. In the Greenland capital of Nuuk, Neptune is occulted by the Moon at 6:59pm WGT when the moon and planet are 16 degrees high in the southern sky.
In New York, New York the sun is still above the horizon as Neptune is occulted, but the planet reappears at the Moon’s bright limb close to 5:30pm EST. In Boston, Massachusetts, Neptune’s reappearance occurs close to 5:36pm EST.
So for most of us in North America, by the time night falls, the occultation will be over. You would need a telescope to view it, anyway, because Neptune – eighth planet out from the sun and outermost of the major planets according to the International Astronomical Union – is the only major planet in our solar system that you absolutely can’t see with the unaided eye.
— Massimo (@Rainmaker1973) December 4, 2016
On December 6, Neptune shines in front of the constellation Aquarius, and near the star Lambda Aquarii (see chart below).
Neptune is also close to the ecliptic – the path the planets follow in front of the constellations of the zodiac. Because of the moonlit glare, you probably won’t see much of Aquarius tonight. What will you see? Only the moon shining in all its splendor. You can gaze at it and imagine Neptune nearby.
Although the moon and Neptune are close together on the sky’s dome tonight, they’re nowhere close in space. The moon resides just over one light-second from Earth, whereas Neptune looms way out there at over four light-hours away. In other words, Neptune is nearly 12,000 times farther away than the moon in tonight’s sky.
The moon resides about 237,000 miles (380,000 km) from Earth this evening. For a more exact figure of the moon’s distance at present (or a given date), click here.
Once the moon leaves the evening sky, starting in the second half of December, Aquarius will easy to spot in a dark country sky. Then, if you’re armed with a telescope or powerful binoculars and a good sky chart, you might be able to glimpse Neptune.
For a stellar reference, learn how to star-hop to Lambda Aquarii, your guide star to Neptune. Neptune demands high-quality binoculars or a telescope, patience and a detailed star chart. Look for Neptune and the star Lambda Aquarii to take stage within the same binocular field.
Bottom line: On this November night – December 6, 2016 – use your mind’s eye to envision the solar system’s most distant major planet – Neptune – by tonight’s moon.
Bruce McClure has served as lead writer for EarthSky's popular Tonight pages since 2004. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also writes and hosts public astronomy programs and planetarium programs in and around his home in upstate New York.