Washington: The planet Neptune has seasons like Earth. A progressive increase in the brightness of the distant planet is suggestive of this.

Observations of Neptune made during a six-year period with NASA's (National Aerospace and Space Administration) Hubble Space Telescope by a group of scientists from the University of Wisconsin- Madison and NASA's Jet Propulsion Laboratory (JPL) show that the planet is exhibiting a significant increase in brightness.

The changes, observed mostly in the planet's southern hemisphere, show a distinct increase in the amount and brightness of the banded cloud features that are a distinctive feature of the planet.

"Neptune's cloud bands have been getting wider and brighter. This change seems to be a response to seasonal variations in sunlight, like the seasonal changes we see on Earth," said Lawrence A Sromovsky, a senior scientist at UW-Madison's Space Science and Engineering Centre and a leading authority on Neptune's atmosphere.

Neptune, the eighth planet from the Sun, is known for its weird and violent weather. It has massive storm systems and ferocious winds that sometimes gust to 900 miles per hour, but the new Hubble observations are the first to suggest that the planet undergoes a change of seasons.

"Like the Earth, Neptune would have four seasons. Each hemisphere would have a warm summer and a cold winter, with spring and fall being transitional seasons, which may or may not have specific dynamical features," the Wisconsin scientist explained.

Unlike the Earth, however, the seasons of Neptune last for decades, not months. A single season on the planet, which takes almost 165 years to orbit the Sun, can last more than 40 years. If what scientists are observing is truly seasonal change, the planet will continue to brighten for another 20 years.

Also like Earth, Neptune spins on an axis that is tilted at an angle toward the Sun. What is remarkable, according to Sromovsky, is that Neptune exhibits any evidence of seasonal change at all, given that the Sun, as viewed from the planet, is 900 times dimmer than the Sun as seen from the Earth. The amount of solar energy a hemisphere receives at a given time is what determines the season.

ANI