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Gaia finds parts of the Milky Way much older than expected
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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 NASA
X-ray: NASA/CXC/RIT/A. Varga et al.; Illustration: NASA/CXC/SAO/M. Weiss; Image Processing: NASA/CXC/SAO/N. Wolk A star is unleashing a barrage of X-rays that is causing a closely-orbiting, young planet to wither away an astonishing rate, according to a new study using data from NASA’s Chandra X-ray Observatory and described in our latest press release. A team of researchers has determined that this planet will go from the size of Jupiter down to a small, barren world.
This graphic provides a visual representation of what astronomers think is happening around the star (known as TOI 1227) and a planet that is orbiting it at a fraction the distance between Mercury and the Sun. This “baby” planet, called TOI 1227 b, is just about 8 million years old, about a thousand times younger than our Sun. The main panel is an artist’s concept that shows the Jupiter-sized planet (lower left) around TOI 1227, which is a faint red star. Powerful X-rays from the star’s surface are tearing away the atmosphere of the planet, represented by the blue tail. The star’s X-rays may eventually completely remove the atmosphere.
The team used new Chandra data — seen in the inset — to measure the amounts of X-rays from TOI 1227 that are striking the planet. Using computer models of the effects of these X-rays, they concluded they will have a transformative effect, rapidly stripping away the planet’s atmosphere. They estimate that the planet is losing a mass equivalent to a full Earth’s atmosphere about every 200 years.
The researchers used different sets of data to estimate the age of TOI 1227 b. One method exploits measurements of how TOI 1227 b’s host star moves through space in comparison to nearby populations of stars with known ages. A second method compared the brightness and surface temperature of the star with theoretical models of evolving stars. The very young age of TOI 1227 b makes it the second youngest planet ever to be observed passing in front of its host star (a so-called transit). Previously the planet had been estimated by others to be about 11 million years old.
Of all the exoplanets astronomers have found with ages less than 50 million years, TOI 1227 b stands out for having the longest year and the host planet with the lowest mass. These properties, and the high dose of X-rays it is receiving, make it an outstanding target for future observations.
A paper describing these results has been accepted publication in The Astrophysical Journal and a preprint is available here. The authors of the paper are Attila Varga (Rochester Institute of Technology), Joel Kastner (Rochester Institute of Technology), Alexander Binks (University of Tubingen, Germany), Hans Moritz Guenther (Massachusetts Institute of Technology), and Simon J. Murphy (University of New South Wales Canberra in Australia).
NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program. The Smithsonian Astrophysical Observatory’s Chandra X-ray Center controls science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.
Read more from NASA’s Chandra X-ray Observatory Learn more about the Chandra X-ray Observatory and its mission here:
https://www.nasa.gov/chandra
https://chandra.si.edu
Visual Description
This release features an artist’s illustration of a Jupiter-sized planet closely orbiting a faint red star. An inset image, showing the star in X-ray light from Chandra, is superimposed on top of the illustration at our upper left corner.
At our upper right, the red star is illustrated as a ball made of intense fire. The planet, slightly smaller than the star, is shown at our lower left. Powerful X-rays from the star are tearing away the atmosphere of the planet, causing wisps of material to flow away from the planet’s surface in the opposite direction from the star. This gives the planet a slight resemblance to a comet, complete with a tail.
X-ray data from Chandra, presented in the inset image, shows the star as a small purple orb on a black background. Astronomers used the Chandra data to measure the amount of X-rays striking the planet from the star. They estimate that the planet is losing a mass equivalent to a full Earth’s atmosphere about every 200 years, causing it to ultimately shrink from the size of Jupiter down to a small, barren world.
News Media Contact
Megan Watzke
Chandra X-ray Center
Cambridge, Mass.
617-496-7998
mwatzke@cfa.harvard.edu
Corinne Beckinger
Marshall Space Flight Center, Huntsville, Alabama
256-544-0034
corinne.m.beckinger@nasa.gov
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Last Updated Jul 16, 2025 EditorLee MohonContactCorinne M. Beckingercorinne.m.beckinger@nasa.gov Related Terms
Astrophysics Chandra X-Ray Observatory Exoplanet Science Exoplanets Marshall Astrophysics Marshall Space Flight Center Science & Research Studying Exoplanets The Universe Explore More
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By European Space Agency
Astronomers using the NASA/ESA/CSA James Webb Space Telescope have captured compelling evidence of a planet with a mass similar to Saturn orbiting the young nearby star TWA 7.
If confirmed, this would represent Webb’s first direct image discovery of a planet, and the lightest planet ever seen with this technique.
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By NASA
X-ray: NASA/CXC/CfA/Stroe, A. et al.; Optical: PanSTARRS; Radio: ASTRON/LOFAR; Image Processing: NASA/CXC/SAO/N. Wolk New observations from NASA’s Chandra X-ray Observatory and other telescopes have captured a rare cosmic event: two galaxy clusters have collided and are now poised to head back for another swipe at each other.
Galaxy clusters are some of the largest structures in the Universe. Held together by gravity, they are monster-sized collections of hundreds or thousands of individual galaxies, massive amounts of superheated gas, and invisible dark matter.
The galaxy cluster PSZ2 G181.06+48.47 (PSZ2 G181 for short) is about 2.8 billion light-years from Earth. Previously, radio observations from the LOw Frequency ARray (LOFAR), an antenna network in the Netherlands, spotted parentheses-shaped structures on the outside of the system. In this new composite image, X-rays from Chandra (purple) and ESA’s XMM-Newton (blue) have been combined with LOFAR data (red) and an optical image from Pan-STARRs of the stars in the field of view.
These structures are probably shock fronts — similar to those created by jets that have broken the sound barrier — likely caused by disruption of gas from the initial collision about a billion years ago. Since the collision they have continued traveling outwards and are currently separated by about 11 million light-years, the largest separation of these kinds of structures that astronomers have ever seen.
Colliding galaxy clusters PSZ2 G181.06+48.47 (Labeled).X-ray: NASA/CXC/CfA/Stroe, A. et al.; Optical: PanSTARRS; Radio: ASTRON/LOFAR; Image Processing: NASA/CXC/SAO/N. Wolk Now, data from NASA’s Chandra and ESA’s XMM-Newton is providing evidence that PSZ2 G181 is poised for another collision. Having a first pass at ramming each other, the two clusters have slowed down and begun heading back toward a second crash.
Astronomers made a detailed study of the X-ray observations of this collision site and found three shock fronts. These are aligned with the axis of the collision, and the researchers think they are early signs of the second, oncoming crash.
The researchers are still trying to determine how much mass each of the colliding clusters contains. Regardless, the total mass of the system is less than others where galaxy clusters have collided. This makes PSZ2 G181 an unusual case of a lower-mass system involved in the rare event of colliding galaxy clusters.
A paper describing these results appears in a recent issue of The Astrophysical Journal (ApJ) and is led by Andra Stroe from the Center for Astrophysics | Harvard & Smithsonian (CfA) and collaborators. It is part of a series of three papers in ApJ. The second paper is led by Kamlesh Rajpurohit, also of CfA, and the third paper is led by Eunmo Ahn, from Yonsei University in the Republic of Korea.
NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program. The Smithsonian Astrophysical Observatory’s Chandra X-ray Center controls science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.
Read more from NASA’s Chandra X-ray Observatory Learn more about the Chandra X-ray Observatory and its mission here:
https://www.nasa.gov/chandra
https://chandra.si.edu
Visual Description
In this release, a composite image illustrates a dramatic cosmic story unfolding 2.8 billion light years from Earth. Presented both with and without labels, the image details the fallout when two galaxy clusters collide.
At the center of the image are the colliding galaxy clusters, which together are known as PSZ2 G181. This combined cluster somewhat resembles an irregular violet peanut shell, with bulbous ends linked by a tapered middle. Inside each bulbous end are several glowing dots; some of the galaxies within the clusters. The violet peanut shape is tilted at a slight angle, surrounded by a blue haze of X-ray gas.
Far from the bulbous ends, at our upper left and lower right, are two blotchy, thick red lines. These are probably shock fronts, similar to those created by jets that have broken the sound barrier. Bracketing the combined galaxy cluster, these shock fronts were caused by the initial collision about a billion years ago. They are currently separated by 11 million light-years.
New data from the Chandra and XMM-Newton observatories suggests that PSZ2 G181 is poised for another powerful cosmic event. Having already taken one swipe at each other, the two clusters within are once again on a collision course.
News Media Contact
Megan Watzke
Chandra X-ray Center
Cambridge, Mass.
617-496-7998
mwatzke@cfa.harvard.edu
Lane Figueroa
Marshall Space Flight Center, Huntsville, Alabama
256-544-0034
lane.e.figueroa@nasa.gov
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Last Updated Jun 04, 2025 Related Terms
Chandra X-Ray Observatory Galaxies Galaxy clusters Marshall Astrophysics Marshall Space Flight Center The Universe
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By European Space Agency
Over a decade’s worth of NASA/ESA Hubble Space Telescope data was used to re-examine the long-held prediction that the Milky Way galaxy will collide with the Andromeda galaxy in about 4.5 billion years. The astronomers found that, based on the latest observational data from Hubble and Gaia, there is only a 50-50 chance of the two galaxies colliding within the next 10 billion years.
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