Washington : For astronomers, it has been nearly 165 years since Neptune was discovered in 1846. But for Neptune, it has been just one circuit around the Sun.
On Tuesday, the giant blue-green planet reached the same location in the space where it was discovered. And NASA has published new ‘anniversary’ images of Neptune taken by the Hubble Space Telescope to commemorate the event.
Hubble shot four images of Neptune from June 25 to 26, 2011, during the planet’s 16-hour rotation, using the Wide Field Camera 3. The images reveal pinkish high-altitude clouds composed of methane ice crystals in the northern and southern hemispheres.
Neptune is 4.5 billion km from the Sun, 30 times farther than Earth. Under the Sun’s weak pull at that distance, Neptune plods along in its huge orbit, slowly completing one revolution approximately every 165 years.
The giant planet experiences seasons just as Earth does, because it is tilted 29 degrees, similar to Earth’s 23-degree tilt. Instead of lasting a few months, each of Neptune’s seasons continues for about 40 years.
The Hubble snapshots show that Neptune has more clouds than a few years ago, when most of the clouds were in the southern hemisphere.
It reveals that the cloud activity is shifting to the northern hemisphere. It is early summer in the southern hemisphere and winter in the northern hemisphere.
Neptune is not visible to the naked eye, but may be seen in binoculars or a small telescope. It can be found in the constellation Aquarius, close to the boundary with Capricorn.