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Astronomers Discover an Infrared Background Glow in the Universe
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By NASA
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Jupiter, Saturn, and Neptune each emit more energy than they receive from the Sun, meaning they have comparatively warm interiors. NASA’s Uranus flyby with Voyager 2 in 1986 found the planet colder than expected, which challenged ideas of how planets formed and evolved. However, with advanced computer modeling and a new look at old data, scientists think the planet may actually be warmer than previously expected. For millennia, astronomers thought Uranus was no more than a distant star. It wasn’t until the late 18th century that Uranus was universally accepted as a planet. To this day, the ringed, blue world subverts scientists’ expectations, but new NASA research helps puzzle out some of the world’s mystique.
This zoomed-in image of Uranus, captured by the Near-Infrared Camera on NASA’s James Webb Space Telescope on Feb. 6, 2023, reveals stunning views of Uranus’ rings. Credits: NASA, ESA, CSA, STScI Uranus 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.” Uranus also rotates in the opposite direction of all planets except Venus. Data from NASA’s Voyager 2 Uranus flyby in 1986 also suggested the planet is unusually cold inside, challenging scientists to reconsider fundamental theories of how planets formed and evolved 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 Center in Greenbelt, Maryland. “But it’s been really hard to explain why that is, especially when compared with the other giant planets.”
These Uranus projections came from 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.”
Now, using an advanced computer modeling technique and revisiting decades of data, Simon and a team of scientists have found that Uranus does in fact generate some heat, as they reported on May 16 in the Monthly Notices of the Royal Astronomical Society journal.
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 — Saturn, Jupiter, and Neptune — 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 that 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.
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 perhaps 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 planet on its side — blasted out all of Uranus’ heat. But none of these hypotheses satisfied scientists, motivating them to solve Uranus’ cold case.
“We thought, ‘Could it really be that there is no internal heat at Uranus?’” said Patrick Irwin, the paper’s lead author and 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.”
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.
To get the most accurate estimate of Uranus’ energy budget yet, Oxford researchers developed a computer model that brought together everything known about Uranus’ atmosphere from decades of observations from ground- and space-based telescopes, including NASA’s Hubble Space Telescope and NASA’s 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.
These side-by-side images of Uranus, taken eight years apart by NASA’s Hubble Space Telescope, show seasonal changes in the planet’s reflectivity. The left image shows the planet seven years after its northern spring equinox when the Sun was shining just above its equator. The second photo, taken six years before the planet’s summer solstice, portrays a bright and large northern polar cap. Credit: NASA, ESA, STScI, A. Simon (NASA-GSFC), M. H. Wong (UC Berkeley), J. DePasquale (STScI) 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 that was published July 14 in Geophysical Research Letters. These studies suggest Uranus it has its own heat, though still far less than its neighbor 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.
Unraveling 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.
By Emma Friedman
NASA’s Goddard Space Flight Center, Greenbelt, Md.
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Last Updated Jul 17, 2025 Editor Lonnie Shekhtman Contact Lonnie Shekhtman lonnie.shekhtman@nasa.gov Location NASA Goddard Space Flight Center Related Terms
Planetary Science Planets The Solar System Uranus View the full article
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By European Space Agency
Astronomers have discovered a huge filament of hot gas bridging four galaxy clusters. At 10 times as massive as our galaxy, the thread could contain some of the Universe’s ‘missing’ matter, addressing a decades-long mystery.
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By NASA
NASA’s James Webb Space Telescope recently imaged the Sombrero Galaxy with its NIRCam (Near-Infrared Camera), which shows dust from the galaxy’s outer ring blocking stellar light from stars within the galaxy. In the central region of the galaxy, the roughly 2,000 globular clusters, or collections of hundreds of thousands of old stars held together by gravity, glow in the near-infrared. The Sombrero Galaxy is around 30 million light-years from Earth in the constellation Virgo. From Earth, we see this galaxy nearly “edge-on,” or from the side.NASA, ESA, CSA, STScI After capturing an image of the iconic Sombrero galaxy at mid-infrared wavelengths in late 2024, NASA’s James Webb Space Telescope has now followed up with an observation in the near-infrared. In the newest image, released on June 3, 2025, the Sombrero galaxy’s tightly packed group of stars at the galaxy’s center is illuminated while the dust in the outer edges of the disk blocks some stellar light. Studying galaxies like the Sombrero at different wavelengths, including the near-infrared and mid-infrared with Webb, as well as the visible with NASA’s Hubble Space Telescope, helps astronomers understand how this complex system of stars, dust, and gas formed and evolved, along with the interplay of that material.
Learn more about the Sombrero galaxy and what this new view can tell us.
Image credit: NASA, ESA, CSA, STScI
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By NASA
Explore This Section Science Science Activation Take a Tour of the Cosmos with… Overview Learning Resources Science Activation Teams SME Map Opportunities More Science Activation Stories Citizen Science 4 min read
Take a Tour of the Cosmos with New Interactives from NASA’s Universe of Learning
Ready for a tour of the cosmos? NASA’s Universe of Learning has released a new, dynamic way for lifelong learners to explore NASA’s breathtaking images of the universe—ViewSpace interactive Image Tours. ViewSpace has an established track record of providing museums, science centers, libraries, and other informal learning environments with free, web-based videos and digital interactives—like its interactive Image Sliders. These new Image Tours are another unique experience from NASA’s Universe of Learning, created through a collaboration between scientists that operate NASA telescopes and experts well-versed in the most modern methods of learning. Hands-on, self-directed learning resources like these have long been valued by informal learning sites as effective means for engaging and intriguing users with the latest discoveries from NASA’s space telescope missions—while encouraging lifelong learners to continue their passionate exploration of the stars, galaxies, and distant worlds.
With these new ViewSpace Image Tours, visitors can take breathtaking journeys through space images that contain many exciting stories. The “Center of the Milky Way Galaxy” Tour, for example, uses breathtaking images from NASA’s Hubble, Spitzer, and Chandra X-ray telescopes and includes eleven Tour Stops, where users can interact with areas like “the Brick”—a dense, dark cloud of hydrogen molecules imaged by Spitzer. Another Tour Stop zooms toward the supermassive black hole, Sagittarius A*, offering a dramatic visual journey to the galaxy’s core.
In other tours, like the “Herbig-Haro 46/47” Tour, learners can navigate through points of interest in an observation from a single telescope mission. In this case, NASA’s James Webb Space Telescope provides the backdrop where lifelong learners can explore superheated jets of gas and dust being ejected at tremendous speeds from a pair of young, forming stars. The power of Webb turns up unexpected details in the background, like a noteworthy distant galaxy famous for its uncanny resemblance to a question mark. Each Interactive Image Tour allows people to examine unique features through videos, images, or graphical overlays to identify how those features have formed in ways that static images alone can’t convey.
These tours, which include detailed visual descriptions for each Tour Stop, illuminate the science behind the beauty, allowing learners of all ages to develop a greater understanding of and excitement for space science, deepening their engagement with astronomy, regardless of their prior experience. Check out the About the Interactives page on the ViewSpace website for a detailed overview of how to use the Image Tours.
ViewSpace currently offers three Image Tours, and the collection will continue growing:
Center of the Milky Way Galaxy:
Peer through cosmic dust and uncover areas of intense activity near the Milky Way’s core, featuring imagery from the Hubble Space Telescope, Spitzer Space Telescope, and the Chandra X-ray Observatory.
Herbig-Haro 46/47:
Witness how a tightly bound pair of young stars shapes their nebula through ejections of gas and dust in an image from the James Webb Space Telescope.
The Whirlpool Galaxy:
Explore the iconic swirling arms and glowing core of a stunning spiral galaxy, with insights into star formation, galaxy structure, and more in a Hubble Space Telescope image.
“The Image Tours are beautiful, dramatic, informational, and easy to use,” explained Sari Custer, Chief of Science and Curiosity at Arizona Science Center. “I’m excited to implement them in my museum not only because of the incredible images and user-friendly features, but also for the opportunity to excite and ignite the public’s curiosity about space.”
NASA’s Universe of Learning is supported by NASA under cooperative agreement award number NNX16AC65A and is part of NASA’s Science Activation Portfolio. Learn more about how Science Activation connects NASA science experts, real content, and experiences with community leaders to do science in ways that activate minds and promote deeper understanding of our world and beyond: https://science.nasa.gov/learn/about-science-activation/
Select views from various Image Tours. Clockwise from top left: The Whirlpool Galaxy, Center of the Milky Way Galaxy, Herbig-Haro 46/47, detail view in the Center of the Milky Way Galaxy. Share
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Last Updated May 13, 2025 Editor NASA Science Editorial Team Related Terms
Science Activation Astrophysics For Educators Explore More
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