Mars and Neptune will share the same right ascension, with Mars passing 1'14" to the south of Neptune.
At around the same time, the two objects will also make a close approach, technically called an appulse.
From Cambridge , the pair will become visible at around 17:35 (EST), 32° above your south-western horizon, as dusk fades to darkness. They will then sink towards the horizon, setting at 21:13.
Mars will be at mag 0.9, and Neptune at mag 7.9, both in the constellation Aquarius.
The pair will be close enough to fit within the field of view of a telescope, but will also be visible through a pair of binoculars.
A graph of the angular separation between Mars and Neptune around the time of closest approach is available here.
The positions of the two objects at the moment of conjunction will be as follows:
| Object | Right Ascension | Declination | Constellation | Magnitude | Angular Size |
| Mars | 22h45m30s | 8°49'S | Aquarius | 0.9 | 5"7 |
| Neptune | 22h45m30s | 8°47'S | Aquarius | 7.9 | 2"2 |
The coordinates above are given in J2000.0. The pair will be at an angular separation of 58° from the Sun, which is in Sagittarius at this time of year.
The sky on 1 Jan 2017
| The sky on 1 January 2017 | ||||||||||||||||||||||||||||||||||
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11% 3 days old |
All times shown in EST.
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Source
The circumstances of this event were computed using the DE430 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).
This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.
Related news
| 19 Nov 2016 | – Neptune ends retrograde motion |
| 16 Jun 2017 | – Neptune enters retrograde motion |
| 05 Sep 2017 | – Neptune at opposition |
| 22 Nov 2017 | – Neptune ends retrograde motion |
Image credit
The Moon in conjunction with Venus and Jupiter, with the Very Large Telescope in the foreground. Image © Y. Beletsky, ESO, 2009.