Uranus coldest mystery solved

 Scientists finally solved, why Uranus is so cold

For millennia, astronomers thought Uranus was no more than a distant star. A pale blue glimmer in the night sky, it wandered slowly across constellations, indistinguishable from the stellar crowd. It wasn’t until the late 18th century that Uranus was universally accepted as a planet, marking a significant breakthrough in planetary science. But even now, centuries later, the ringed, blue world subverts scientists’ expectations, and new NASA research helps puzzle out some of the world’s mystique. For decades, Uranus baffled scientists because it seemed to have no internal heat. Now, new computer modelling shows the planet actually emits more energy than it receives from the Sun. This subtle warmth suggests Uranus’ story is more complex than previously thought, offering fresh clues about its violent past and about exoplanets similar in size.

Uranus does in fact generate some heat. It is unlike any other planet in our solar system. It spins on its side, which means each pole directly faces the Sun for a continuous 42-year “summer.” Imagine a world where seasons last generations, and the Sun hovers over one hemisphere for decades before retreating to the other. Uranus also rotates in the opposite direction to all planets except Venus, adding another twist to its cosmic choreography. Uranus spins sideways, flips expectations and has puzzled scientists since Voyager 2 revealed its surprising chill in 1986. Fresh analysis now suggests the planet might hold more warmth than once thought. To this day, the ringed, blue world subverts scientists' expectations, but new NASA research helps puzzle out some of the world's mystique. However, with advanced computer modelling and a new look at old data, scientists think the planet may actually be warmer than previously expected.

This peculiar behaviour has long fascinated scientists, particularly after NASA’s Voyager 2 flyby of Uranus in 1986. The spacecraft revealed a planet that was unusually cold inside, prompting scientists to reconsider fundamental theories of how planets form and evolve throughout our solar system. “Since Voyager 2’s flyby, everybody has said Uranus has no internal heat,” said Amy Simon, a planetary scientist at NASA’s Goddard Space Flight Centre in Greenbelt, Maryland. “But it’s been tough to explain why that is, especially when compared with the other giant planets.” These Uranus projections were based on only one up-close measurement of the planet’s emitted heat, made by Voyager 2. “Everything hinges on that one data point,” said Simon. “That is part of the problem.” However, with advanced computer modelling and a new examination of old data, scientists believe the planet is warmer than previously expected.

Uranus stood out from the other planets because it appeared to give off as much heat as it received, implying it had none of its own. This puzzled scientists. Some hypothesized that the planet is much older than all the others and has cooled off completely. Others proposed that a giant collision, the same one that may have knocked the Earth on its side, blasted out all of Uranus’ heat. However, none of these hypotheses satisfied scientists, motivating them to solve Uranus’ long-standing mystery. “We thought, ‘Could it really be that there is no internal heat at Uranus?'” said Patrick Irwin, professor of planetary physics at the University of Oxford in England. “We did many calculations to see how much sunshine is reflected by Uranus, and we realized that it is actually more reflective than people had estimated.” To obtain the most accurate estimate of Uranus’ energy budget yet, Oxford researchers developed a computer model that combined all known information about Uranus’ atmosphere from decades of observations from ground- and space-based telescopes, including NASA’s Hubble Space Telescope and the NASA Infrared Telescope Facility in Hawaii. The model included information about the planet’s hazes, clouds and seasonal changes, all of which affect how sunlight is reflected and how heat escapes.

The researchers set out to determine Uranus' full energy budget: how much energy it receives from the Sun compared to how much it reflects as sunlight and how much it emits as heat. To do this, they needed to estimate the total amount of light reflected from the planet at all angles. "You need to see the light that's scattered off to the sides, not just coming straight back at you," Simon said. A planet's internal heat can be calculated by comparing the amount of energy it receives from the Sun to the amount it of energy it releases into space in the form of reflected light and emitted heat. The solar system's other giant planets like Saturn, Jupiter and Neptune etc emit more heat than they receive, which means the extra heat is coming from inside, much of it left over from the high-energy processes which formed the planets 4.5 billion years ago. The amount of heat a planet exudes could be an indication of its age: the less heat released relative to the heat absorbed from the Sun, the older the planet is.

The researchers found that Uranus releases about 15% more energy than it receives from the Sun, a figure that is similar to another recent estimate from a separate study funded in part by NASA. These studies suggest Uranus has its own heat, though still far less than its neighbour Neptune, which emits more than twice the energy it receives. "Now we have to understand what that remnant amount of heat at Uranus means, as well as get better measurements of it," Simon said. Unravelling Uranus' past is useful not only for mapping the timeline of when solar system planets formed and migrated to their current orbits, but it also helps scientists better understand many of the planets discovered outside the solar system, called exoplanets, a majority of which are the same size as Uranus. In other words, Uranus is a blueprint. Its strange tilt, faint rings, icy moons and now its subtle warmth offer clues not just about our own solar system, but about the thousands of ice giants orbiting distant stars. As scientists prepare for future missions to Uranus, this once-forgotten world is finally stepping into the spotlight, not as a cold relic, but as a dynamic planet with secrets still to shared with the world.