Neptune at solar conjunction

2015 Feb 26

Dominic Ford – originally published on

From our vantage point on the Earth, Neptune will appear very close to the Sun in the sky as it passes around the far side of the solar system from the Earth.

At closest approach, Neptune and the Sun will appear at a separation of only 0°43', making Neptune totally unobservable for several weeks while it is lost in the Sun’s glare.

At around the same time, Neptune will also be at its most distant from the Earth – receding to a distance of 30.96 AU – since the two planets will lie on opposite sides of the solar system.

If Neptune could be observed at this time, it would appear at its smallest and faintest on account of its large distance. It would measure 2.2 arcsec in diameter.

Over following weeks and months, Neptune will re-emerge to the west of the Sun, gradually becoming visible for ever-longer periods in the pre-dawn sky. After around six months, it will reach opposition, when it will be visible for virtually the whole night. A chart of the path of Neptune across the night sky can be found here, and a chart of its rising and setting times here.

The position of Neptune at the moment it passes solar conjunction will be:

Object Right Ascension Declination Constellation Angular Size
Neptune 22h36m10s -09°35' Aquarius 2.2"
Sun 22h35m -08°55' Aquarius 32'18"

The coordinates above are given in J2000.0.

The details of this observing event were provided courtesy of