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- WASP-18b is a hot Jupiter exoplanet about 400 light-years from Earth.<\/strong> The same side of this scorching-hot planet always faces its star.<\/li>\n
- Astronomers created a 3D temperature map of WASP-18b.<\/strong> It is the 1st such map of an exoplanet ever achieved. What does it show?<\/li>\n
- The map reveals distinct variations<\/strong> in temperature and chemical composition of the atmosphere on the side of the planet facing its star.<\/li>\n<\/ul>\n
Millions come to EarthSky for night sky news and trusted science.<\/strong>
Your donation keeps us free and accessible for all.<\/p>\n1st 3D temperature map of exoplanet<\/h3>\n
For the first time, astronomers have created a three-dimensional (3D) temperature map of a distant exoplanet. The planet, WASP-18b, is a scorching ultra-hot Jupiter about 400 light-years away. The researchers, co-led by the University of Maryland in College Park and Cornell University in Ithaca, New York, said on October 28, 2025, that the map revealed three distinct temperature zones. This is the first time astronomers have used a technique called 3D eclipse mapping, or spectroscopic eclipse mapping.<\/p>\n
The new study uses data from NASA\u2019s James Webb Space Telescope. With the same data, some of the researchers in this study had previously created a 2D map of the same planet in 2023.<\/p>\n
WASP-18b has a mass equivalent to 10 Jupiters. Being very close to its star, it completes an orbit in only 23 hours<\/em>. Consequently, this also means it is extremely hot, with a temperature of almost 5,000 degrees Fahrenheit (2,760 degrees Celsius).<\/p>\n
The peer-reviewed results of the new study were published in Nature Astronomy<\/em> on October 28, 2025.<\/p>\n
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#UMD astronomer Megan Weiner Mansfield co-led the creation of the first 3D temperature map for a distant exoplanet.Published in Nature Astronomy, the team’s technique lays the groundwork for more detailed future explorations of faraway planets. ?<\/p>\n
\u2014 UMD Science (@umdscience.bsky.social) 2025-11-04T23:19:02.257Z<\/p>\n<\/blockquote>\n
Mapping a distant exoplanet<\/h3>\n
Astronomers used an eclipse mapping<\/em> technique so they could see the exoplanet\u2019s temperatures in 3D. Despite the star and planet\u2019s huge size differences, astronomers can detect tiny changes from the light of a planet as its star starts to pass in front of \u2013 or eclipse \u2013 the planet. The press release explained: <\/p>\n
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Scientists can link minute changes in light to an exoplanet\u2019s specific regions to produce a brightness map that, when rendered in multiple colors, can map out temperatures in latitude, longitude and altitude.<\/p>\n<\/blockquote>\n
As co-lead author Megan Weiner Mansfield at the University of Maryland said:<\/p>\n
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This technique is really the only one that can probe all three dimensions at once: latitude, longitude and altitude. This gives us a higher level of detail than we\u2019ve ever had to study these celestial bodies.<\/p>\n<\/blockquote>\n
A map of the exoplanet\u2019s atmosphere<\/h3>\n
Since WASP-18b is a gas giant planet, astronomers can only map its outer atmosphere. But the mapping can reveal variations in the clouds and temperature of the atmosphere. Ryan Challener, the other co-lead author at Cornell University, said:<\/p>\n
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Eclipse mapping allows us to image exoplanets that we can\u2019t see directly, because their host stars are too bright. With this telescope and this new technique, we can start to understand exoplanets along the same lines as our solar system neighbors.<\/p>\n<\/blockquote>\n
![\"Chart](\"https:\/\/earthsky.org\/upl\/2025\/11\/WASP-18b-2D-maps-single-wavelength-Nature-Astronomy-October-28-2025.jpeg\")
View larger. | Set of 2D maps for 25 different light wavelengths showing WASP-18b. The researchers then combined the individual maps to create the 3D temperature map. Image via Challener et al.\/ Nature Astronomy (Open Access\/ CC BY 4.0).<\/figcaption><\/figure>\n Observing in many wavelengths<\/h3>\n
For the previous 2D map, researchers used only one wavelength of light. But the new 3D map uses many different wavelengths. The Webb telescope\u2019s Near-Infrared Imager and Slitless Spectrograph (NIRISS) instrument made the observations. Various colors in the map refer to different temperatures and altitudes in the planet\u2019s atmosphere. As Challener explained:<\/p>\n
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If you build a map at a wavelength that water absorbs, you\u2019ll see the water deck in the atmosphere, whereas a wavelength that water does not absorb will probe deeper. If you put those together, you can get a 3D map of the temperatures in this atmosphere.<\/p>\n<\/blockquote>\n
Distinct regions in the atmosphere<\/h3>\n
Overall, the results show that WASP-18b has distinct regions or zones in its atmosphere on the dayside of the planet. WASP-18b is tidally locked to its star. This means that the same side of the planet always faces the star. That\u2019s the planet\u2019s dayside. This is similar to how the same side of the moon always faces Earth. On WASP-18b, the regions vary in both temperature and chemical composition.<\/p>\n
Also, in the area where the light from the star most directly hits the planet, there is a \u201chot spot.\u201d A colder \u201cring\u201d surrounds the hot spot. The researchers said the hot spot and ring are due to winds not being strong enough to redistribute the heat from the hot spot into the surrounding atmosphere. In addition, there is less water vapor in the hot spot than the average for the planet overall. This is the first time such variations have been mapped on a single exoplanet. Mansfield said:<\/p>\n
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We\u2019ve seen this happen on a population level, where you can see a cooler planet that has water and then a hotter planet that doesn\u2019t have water. But this is the first time we\u2019ve seen this be broken across one planet instead. It\u2019s one atmosphere, but we see cooler regions that have water and hotter regions where the water\u2019s being broken apart. That had been predicted by theory, but it\u2019s really exciting to actually see this with real observations.<\/p>\n<\/blockquote>\n
![\"Smiling](\"https:\/\/earthsky.org\/upl\/2025\/11\/Ryan-Challener-Cornell-University.jpg\")
Ryan Challener at Cornell University is the co-lead author of the new study about WASP-18b. Image via Cornell University.<\/figcaption><\/figure>\n ![\"Smiling](\"https:\/\/earthsky.org\/upl\/2025\/11\/Megan-Mansfield-University-of-Maryland.jpg\")
Megan Weiner Mansfield at the University of Maryland is the co-lead author of the new study about WASP-18b. Image via GitHub.<\/figcaption><\/figure>\n Using the 3D temperature map for more hot Jupiters<\/h3>\n
Now, the researchers want this 3D mapping technique to be extended to other hot Jupiters as well. And indeed, astronomers have already found hundreds of them. It is also hoped that astronomers will be able to produce similar 3D maps of smaller rocky exoplanets, too. That would be exciting, because some of them could be potentially habitable for life. As Mansfield explained:<\/p>\n
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It\u2019s very exciting to finally have the tools to see and map out the temperatures of a different planet in this much detail. It\u2019s set us up to possibly use the technique on other types of exoplanets. For example, if a planet doesn\u2019t have an atmosphere, we can still use the technique to map the temperature of the surface itself to possibly understand its composition. Although WASP-18b was more predictable, I believe we will have the chance to see things that we could never have expected before.<\/p>\n<\/blockquote>\n
Last February, another group of astronomers announced the first 3D weather map of an exoplanet, another hot Jupiter called WASP-121b. That one, however, was a weather<\/em> map, while the new one is the temperature<\/em> map. The researchers used the ESPRESSO instrument on the Very Large Telescope (VLT) in Chile to make the previous weather map.<\/p>\n
Bottom line: Astronomers have created the 1st 3D temperature map of a distant exoplanet. The planet, WASP-18b, is a scorching ultra-hot Jupiter 400 light-years away.<\/p>\n
Source: Horizontal and vertical exoplanet thermal structure from a JWST spectroscopic eclipse map<\/p>\n
Via University of Maryland<\/p>\n
Read more: Double hot Jupiters: How do these rare gigantic worlds form?<\/p>\n
Read more: Our 1st 3D weather map from a distant exoplanet<\/p>\n
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\n - Astronomers created a 3D temperature map of WASP-18b.<\/strong> It is the 1st such map of an exoplanet ever achieved. What does it show?<\/li>\n