Sep 9, 2019

Eye on Neptune

It is an ice giant, a planet of monster storms, and a recluse rarely seen. However on the night of September 9 the planet Neptune will be at opposition, the yearly event where Earth passes directly between Neptune and our Sun. Sky watchers and astronomers will take the opportunity to observe this planet that is invisible to the naked eye, but that scientists would love to see more clearly.


When it is near opposition, Neptune reaches its highest point in the sky around midnight. This makes evenings in September the best time to grab your telescope or high-powered binoculars, and use a sky chart or sky watching software to view this planet that is 30 times farther from the Sun than Earth. When you find this elusive planet that appears as a mere dot in most amateur telescopes, remember that you’re actually viewing a planet with a thick atmosphere that is composed of massive amounts of hydrogen and helium with traces of other gasses. That atmosphere surrounds a solid interior of rock and a warm mantle of dense fluid, deep beneath the clouds. 

This opposition event also comes just after the 30thanniversary of the Voyager 2 spacecraft’s flyby of the planet, in 1989. Voyager 2 provided our closest glimpse of Neptune, passing about 3,000 miles (5000 kilometers) above its North Pole. The pictures Voyager 2 sent back gave scientists a new snapshot of weather in the extreme, including a dark and violent vortex that looked similar to the great red spot on Jupiter. Since then, observatories such as the Hubble Space Telescope have given us additional observations of the planet from afar. NASA scientists have learned, for instance, that unlike Jupiter, the Neptune vortex disappears for a time, and then similar storms appear later. Scientists have determined that Neptune has seasons such as those on Earth, but that these are much longer, spanning decades instead of months. By studying these seasons on a continual basis, scientists look to gain a better understanding of the similarities and differences of atmospheres on other planets, including right here on Earth. 

So consider taking a look at the ice giant planet Neptune in September, and you’ll see why it captures the imagination of so many scientists and astronomers. Grab your telescope, step outside, andenjoy the view. 

For more details on Neptune and the other planets in our solar system, visit