The forecast on planet Neptune is cold – and colder

WASHINGTON – Cold and distant Neptune, the outermost planet of our Solar System, is adding to its reputation as a world of mystery, baffling astronomers by the dramatic drop marvel at its atmospheric temperature over the past two decades.

Focusing on Neptune’s stratosphere – the relatively stable region of the atmosphere above the turbulent weather layer – the researchers expected to find increased temperatures in the visible part of the planet. seen from Earth at the onset of summer in its southern hemisphere, a season that spans four decades. Instead, they noticed a significant drop in temperature.

The study is based on more than 95 thermal infrared images – each of which has ever been taken – spanning 2003 to 2020 using ground-based telescopes in Hawaii and Chile, primarily the Radio giant’s Very Large Telescope. Observe Southern Europe. This is the most comprehensive assessment to date of Neptune’s atmospheric temperature.

Michael Roman, a postdoctoral researcher at the University of Leicester, UK and lead author of the study published Monday in Planetary Science Magazine.

Neptune’s stratospheric temperatures dropped by as much as 14 degrees Fahrenheit (8 degrees Celsius) to minus 179 degrees Fahrenheit (minus 117 degrees Celsius) during the 17 years studied. In contrast, temperatures in Neptune’s troposphere – the even colder weather layer – showed no significant change down to minus 370 F (minus 223 C).

Neptune is one of the least explored of the eight planets of the solar system, with a great distance making it difficult to study from Earth. NASA’s Voyager 2 is the only spacecraft to have made a close-up visit, passing Neptune in 1989.

“I think Neptune is very appealing to many of us because we still know so little about it,” says Roman.

Its temperature variation is unevenly distributed, with regional variations. The southern tropics cool, then warm, then cool again. Temperatures at mid-latitudes are initially constant before gradually decreasing. South Pole temperatures initially decreased only slightly before warming significantly between 2018 and 2020.

“I suspect the overall drop in temperature is most likely due to changes in atmospheric chemistry, in response to changes in seasonal sunlight and changes in how much the atmosphere cools,” said Roman. ozone.

Neptune’s average diameter is about 30,600 miles (49,250 km), four times wider than Earth’s. It orbits 30 times farther from the sun than Earth at an average distance of about 2.8 billion miles (4.5 billion kilometers), taking about 165 Earth years to complete one orbit around the sun – a Neptune year.

The dwarf planet Pluto most of the time orbits further away, but its oval orbit sometimes brings it closer to the sun than Neptune.

Neptune and neighboring Uranus are classified as ice giants, in contrast to the gas giants Jupiter and Saturn. Neptune, like other planets without a solid surface, possesses an extremely dynamic atmosphere of mainly hydrogen and helium, with small amounts of methane, atop a mantle of mainly dilute ammonia and water and a solid core. Neptune boasts the strongest winds of any planet.

Glenn Orton study co-author Glenn Orton, a planetary scientist at Caltech’s Jet Propulsion Laboratory, said Neptune could offer lessons about planets beyond its solar system. we.

“The close relationship that Neptune may share with a large portion of the alien planet population,” Orton said, “means it could be ‘an alien planet in our backyard. us’ – possibly at the colder end of that spectrum, but still a model for what we can expect to see in the meteorology of various exoplanets. “

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