For centuries, Uranus has been considered a star far away. It was a pale blue star in the sky that moved slowly through constellations and could not be distinguished from other stars. Uranus wasn’t accepted by all scientists as a world until the 18th century, which was a major breakthrough for planetary science. Even today, hundreds of years later, scientists are still surprised by the blue, ringed world. New NASA research is helping to unravel some of its mystique.
Uranus differs from every other planet within our solar system. The planet spins sideways, so that each pole faces directly the Sun during a 42-year continuous “summer”. Imagine living in a world with seasons lasting generations and where the Sun is hovering over one hemisphere before moving to the opposite. Uranus rotates the other way around than all of its planets, except Venus. This adds another dimension to Uranus’s cosmic dance.
Scientists have been fascinated by this peculiar behavior for a long time, especially after NASA’s Voyager 2 flew past Uranus back in 1986. This spacecraft showed a planet with an unusually cool interior, which prompted scientists to rethink fundamental theories about how planets are formed and evolve in our solar system.
Since Voyager 2 flew by, everyone has claimed Uranus does not have internal heat. Amy Simon is a NASA Goddard Space Flight Center scientist in Greenbelt. It’s hard to understand why, particularly when you compare it with other planets.
Japanese astronomers reveal the strange origins of Uranus
Voyager 2 measured the heat emitted by Uranus, but this was only one measurement. The entire world depends on this one single data point. Simon said This is a part of the issue.
Scientists believe that the Earth is actually warmer than they thought, thanks to advanced computer models and an updated analysis of older data.
Simon and his team of researchers have now found, by using a computer model and revisiting data from decades ago, that Uranus, indeed, produces heat. They reported their findings in the Monthly Notices of Royal Astronomical Society.
Calculating a planet’s heat inside is as simple as comparing how much energy the Sun sends to it with the heat and light it emits into the space. Saturn, Jupiter and Neptune are the other solar system giants that emit more heat. This means they get it from within, a lot of which is leftover heat from high-energy processes 4.5 billions years ago when the planets were formed. Heat emitted by a planet can be a good indicator of its age. The less heat the planet produces in comparison to heat that it absorbs from the Sun the older the planet will be.
The first X-rays discovered from Uranus
Uranus was different from other planets in that it seemed to emit as much heat it received. This implied it did not have its own. Scientists were puzzled by this. Scientists hypothesized the planet was much older and had cooled completely. Some hypothesized that Uranus lost its heat due to a massive collision that knocked Earth onto its side. Scientists were not satisfied with any of the hypotheses, and they set out to find a solution for Uranus.
We thought, “Could there really be no heat inside Uranus?” ‘” Patrick Irwin is the lead author of the article and professor of planetary physics at Oxford University in England. We did several calculations to determine how much sunlight is reflected from Uranus. It was more than we had thought.
Researchers set out to calculate Uranus’s total energy budget. They wanted to know how much Uranus receives from sunlight, how much heat it produces and how much it radiates. In order to do so, the researchers needed an estimate of the amount of total light that was reflected by the planet from all angles. You need to be able to distinguish between light coming from the side and the back. Simon Said
Researchers at Oxford developed the best estimate yet of Uranus’ energy budget by developing a computer-based model. This combined information from decades worth of observations made from both ground and space telescopes. These included NASA’s Hubble Space Telescope, and NASA Infrared Telescope Facility, located in Hawaii. Model included data on the planet’s clouds, hazes and seasonal variations, which all affect how light is reflected.
Astronomers confirm the presence of a infrared aurora at Uranus
Researchers found Uranus emits about 15% more than the energy it receives. This is similar to a recent estimate published in Geophysical Research Letters on 14 July, which was funded by NASA. The studies indicate that Uranus emits its own heat. However, it is still much less than Neptune which produces more than double the amount of energy.
Now we need to better understand the remnant heat on Uranus and get more accurate measurements. Simon Said
Scientists can use Uranus’ past to map the formation and migration of solar system planets. They also gain a better understanding of exoplanets that are similar in size to Uranus.
Uranus, in other words is a template. Uranus’s tilting, its faint rings, the icy moons and, now, even its slight warmth, provide clues about not only our solar system but also about thousands of distant ice giants. Scientists are preparing for missions to Uranus. This once forgotten world, which was previously viewed as an icy relic is now being brought into the light as it has secrets to reveal.
Journal references:
- Patrick G J Irwin. Daniel D Wenkert. Amy A Simon. Emma Dahl. Heidi B Hammel. Uranus’ bolometric Bond Albedo. Monthly Notices of the Royal Astronomical Society, 2025; 540 (2): 1719 DOI: 10.1093/mnras/staf800
- Xinyue Wang, Liming Li, Michael Roman, Xi Zhang, Xun Jiang, Patrick Fry, Cheng Li, Gwenael Milcareck, Agustin Sanchez-Lavega, Santiago Perez-Hoyos, Ricardo Hueso, Tristan Guillot, Conor Nixon, Ulyana Dyudina, Robert West, Matthew Kenyon. Uranus’ Internal Heat Flux, and its Energy Imbalance. Geophysical Research Letters 2025, 52 (14): DOI 10.1029/2025GL115660
