It’s getting hot and, er, gassy on Uranus.
A deep, long probe of the bluish gas giant has revealed that it leaks far more heat than it receives from the Sun.
The seventh planet in the solar system has an average temperature of just -195°C, unsurprising given it’s 1.8billion miles from the Sun.
But scientists now say that Uranus is actually warmed from the inside, according to a study published in Geophysical Research Letters.
Lead researcher Dr Xinyue Wang, of the University of Houston, said: ‘From a scientific perspective, this study helps us better understand Uranus and other giant planets.’
Uranus is an ice giant, so-called because of the freezing conditions in which it formed 4.5billion years ago, when gravity squeezed gas and dust together not far from the Sun before drifting outwards.
Most of what we understand about Uranus comes from a brief flyby that NASA’s Voyager 2 spacecraft did in 1986, when it snapped photos of the planet as a featureless light-blue blob.
Voyager 2 picked up no internal heat from Uranus, being about the temperature scientists would expect if it were only heated by the Sun.
Yet when it whizzed by Jupiter, Saturn and Neptune, the craft found they all radiated 100% more energy into space than they received from the Sun.
This made Uranus something of a planetary pariah, with scientists having no clue why the ice giant’s internal temperature was so low.
But when Dr Wang and her team looked into an archive of data about Uranus, they found it emits 12.5% more heat than it receives from the Sun.
Dr Wang said: ‘This means it’s still slowly losing leftover heat from its early history, a key piece of the puzzle that helps us understand its origins and how it has changed over time.’
Dr Wang said that the Voyager 2 probe may have caught Uranus at a strange time, such as a surge in solar weather or how it was at solstice.
The planet’s energy levels also seem to change with its 20-year-long seasons, with these changes making Uranus’ orbit and spin wobbly.
So while Uranus probably has internal heat like the other outer planets, it’s still something of a weird cousin to them, with researchers suggesting it might have a ‘different interior structure or evolutionary history’.
Jupiter and Saturn are, broadly speaking, toasty because of gravitational compression – heat is released as gravity squashes them. Why Neptune is warmer than it should be is still something of a mystery, however.
Quick Uranus facts
- Uranus is four times wider than Earth. If Earth were the size of a 10p coin, Uranus would be about as big as a softball.
- One day on Uranus takes about 17 hours, while a year is 84 Earth years.
- Uranus has two sets of just-about visible rings – nine inner loops and two dusty outer ones which have a reddish tint.
- The planet’s core is about the size of Mercury and is 4,982°C.
- The gas giant is, well, gassy, with an atmosphere made of hydrogen, helium and methane, which gives it a blue colour.
- It’s pretty windy on Uranus, with speeds reaching up to 560mph.
Liming Li, co-author and professor in UH’s Department of Physics, said the study shows why it’s so important we get up, close and personal with Uranus.
After all, scientists have upended what they assumed about Uranus over the years, such as it likely being awash with 5,000-mile deep oceans and its moons supporting life.
‘By uncovering how Uranus stores and loses heat, we gain valuable insights into the fundamental processes that shape planetary atmospheres, weather systems and climate systems,’ she said.
‘These findings help broaden our perspective on Earth’s atmospheric system and the challenges of climate change.’
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