Neptune at Opposition

Never seen Neptune? Now is a good time to try, as the icy blue giant reaches opposition and appears at its biggest and brightest of the year.

On the night of September 10, Neptune will be directly opposite the sun in the sky. At opposition, the ice giant will be closest to Earth for the year and visible all night long.

For skywatchers the opposition of Neptune means that they will have a chance to see the eighth planet of the Solar system at its bluest, largest and brightest. Tiny, blue planet will shine at magnitude 7.8, so even at its closest approach, it won't be possible to see Neptune with the naked eye. You will need a telescope to hunt the planet in the southern sky.

Neptune will rise at dusk and sink below the horizon at dawn. You can find it among the stars of Aquarius (the Water-Bearer), just to the left (celestial east) of a medium-bright naked-eye star named Phi (φ) Aquarii. Being so close together, both the star and Neptune will appear together in the field of view of a backyard telescope at medium power. Blue Neptune’s light has been travelling for 4 hours to reach your eye, while the warmly-tinted light of Phi Aquarii has been journeying for 202 years. A bit later the distance between the two objects will increase due to Neptune’s eastward orbital motion.

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Happy hunting!