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By NASA
5 min read
Astronomers Map Stellar ‘Polka Dots’ Using NASA’s TESS, Kepler
Scientists have devised a new method for mapping the spottiness of distant stars by using observations from NASA missions of orbiting planets crossing their stars’ faces. The model builds on a technique researchers have used for decades to study star spots.
By improving astronomers’ understanding of spotty stars, the new model — called StarryStarryProcess — can help discover more about planetary atmospheres and potential habitability using data from telescopes like NASA’s upcoming Pandora mission.
“Many of the models researchers use to analyze data from exoplanets, or worlds beyond our solar system, assume that stars are uniformly bright disks,” said Sabina Sagynbayeva, a graduate student at Stony Brook University in New York. “But we know just by looking at our own Sun that stars are more complicated than that. Modeling complexity can be difficult, but our approach gives astronomers an idea of how many spots a star might have, where they are located, and how bright or dark they are.”
A paper describing StarryStarryProcess, led by Sagynbayeva, published Monday, August 25, in The Astrophysical Journal.
Watch to learn how a new tool uses data from exoplanets, worlds beyond our solar system, to tell us about their polka-dotted stars.
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NASA’s TESS (Transiting Exoplanet Survey Satellite) and now-retired Kepler Space Telescope were designed to identify planets using transits, dips in stellar brightness caused when a planet passes in front of its star.
These measurements reveal how the star’s light varies with time during each transit, and astronomers can arrange them in a plot astronomers call a light curve. Typically, a transit light curve traces a smooth sweep down as the planet starts passing in front of the star’s face. It reaches a minimum brightness when the world is fully in front of the star and then rises smoothly as the planet exits and the transit ends.
By measuring the time between transits, scientists can determine how far the planet lies from its star and estimate its surface temperature. The amount of missing light from the star during a transit can reveal the planet’s size, which can hint at its composition.
Every now and then, though, a planet’s light curve appears more complicated, with smaller dips and peaks added to the main arc. Scientists think these represent dark surface features akin to sunspots seen on our own Sun — star spots.
The Sun’s total number of sunspots varies as it goes through its 11-year solar cycle. Scientists use them to determine and predict the progress of that cycle as well as outbreaks of solar activity that could affect us here on Earth.
Similarly, star spots are cool, dark, temporary patches on a stellar surface whose sizes and numbers change over time. Their variability impacts what astronomers can learn about transiting planets.
Scientists have previously analyzed transit light curves from exoplanets and their host stars to look at the smaller dips and peaks. This helps determine the host star’s properties, such as its overall level of spottiness, inclination angle of the planet’s orbit, the tilt of the star’s spin compared to our line of sight, and other factors. Sagynbayeva’s model uses light curves that include not only transit information, but also the rotation of the star itself to provide even more detailed information about these stellar properties.
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This artist’s concept illustrates the varying brightness of star with a transiting planet and several star spots. NASA’s Goddard Space Flight Center “Knowing more about the star in turn helps us learn even more about the planet, like a feedback loop,” said co-author Brett Morris, a senior software engineer at the Space Telescope Science Institute in Baltimore. “For example, at cool enough temperatures, stars can have water vapor in their atmospheres. If we want to look for water in the atmospheres of planets around those stars — a key indicator of habitability — we better be very sure that we’re not confusing the two.”
To test their model, Sagynbayeva and her team looked at transits from a planet called TOI 3884 b, located around 141 light-years away in the northern constellation Virgo.
Discovered by TESS in 2022, astronomers think the planet is a gas giant about five times bigger than Earth and 32 times its mass.
The StarryStarryProcess analysis suggests that the planet’s cool, dim star — called TOI 3384 — has concentrations of spots at its north pole, which also tips toward Earth so that the planet passes over the pole from our perspective.
Currently, the only available data sets that can be fit by Sagynbayeva’s model are in visible light, which excludes infrared observations taken by NASA’s James Webb Space Telescope. But NASA’s upcoming Pandora mission will benefit from tools like this one. Pandora, a small satellite developed through NASA’s Astrophysics Pioneers Program, will study the atmospheres of exoplanets and the activity of their host stars with long-duration multiwavelength observations. The Pandora mission’s goal is to determine how the properties of a star’s light differs when it passes through a planet’s atmosphere so scientists can better measure those atmospheres using Webb and other missions.
“The TESS satellite has discovered thousands of planets since it launched in 2018,” said Allison Youngblood, TESS project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “While Pandora will study about 20 worlds, it will advance our ability to pick out which signals come from stars and which come from planets. The more we understand the individual parts of a planetary system, the better we understand the whole — and our own.”
Facebook logo @NASAUniverse @NASAUniverse Instagram logo @NASAUniverse By Jeanette Kazmierczak
NASA’s Goddard Space Flight Center, Greenbelt, Md.
Media Contact:
Alise Fisher
202-358-2546
alise.m.fisher@nasa.gov
NASA Headquarters, Washington
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Last Updated Aug 25, 2025 Related Terms
Astrophysics Exoplanet Atmosphere Exoplanets Galaxies, Stars, & Black Holes Galaxies, Stars, & Black Holes Research Goddard Space Flight Center Kepler / K2 Stars TESS (Transiting Exoplanet Survey Satellite) The Universe View the full article
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By NASA
ESA/Hubble & NASA, J. Bally, M. Robberto NASA’s Hubble Space Telescope captured a bright variable star, V 372 Orionis, and its companion in this festive image in this image released on Jan. 27, 2023. The pair lie in the Orion Nebula, a colossal region of star formation roughly 1,450 light-years from Earth.
V 372 Orionis is a particular type of variable star known as an Orion Variable. These young stars experience some tempestuous moods and growing pains, which are visible to astronomers as irregular variations in luminosity. Orion Variables are often associated with diffuse nebulae, and V 372 Orionis is no exception; the patchy gas and dust of the Orion Nebula pervade this scene.
Text credit: European Space Agency (ESA)
Image credit: ESA/Hubble & NASA, J. Bally, M. Robberto
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By NASA
Explore HubbleHubble Home OverviewAbout Hubble The History of Hubble Hubble Timeline Why Have a Telescope in Space? Hubble by the Numbers At the Museum FAQs Impact & BenefitsHubble’s Impact & Benefits Science Impacts Cultural Impact Technology Benefits Impact on Human Spaceflight Astro Community Impacts ScienceHubble Science Science Themes Science Highlights Science Behind Discoveries Hubble’s Partners in Science Universe Uncovered Explore the Night Sky ObservatoryHubble Observatory Hubble Design Mission Operations Missions to Hubble Hubble vs Webb TeamHubble Team Career Aspirations Hubble Astronauts NewsHubble News Social Media Media Resources MultimediaMultimedia Images Videos Sonifications Podcasts e-Books Online Activities Lithographs Fact Sheets Posters Hubble on the NASA App Glossary More35th Anniversary Online Activities 3 Min Read Hubble Spots Stellar Sculptors in Nearby Galaxy
This dazzling NASA/ESA Hubble Space Telescope image features the young star cluster NGC 346. Credits: ESA/Hubble & NASA, A. Nota, P. Massey, E. Sabbi, C. Murray, M. Zamani (ESA/Hubble) As part of ESA/Hubble’s 35th anniversary celebrations, ESA is sharing a new image series revisiting stunning, previously released Hubble targets with the addition of the latest Hubble data and new processing techniques.
This new image showcases the dazzling young star cluster NGC 346. Although both the James Webb Space Telescope and Hubble have released images of NGC 346 previously, this image includes new data and is the first to combine Hubble observations made at infrared, optical, and ultraviolet wavelengths into an intricately detailed view of this vibrant star-forming factory.
This dazzling NASA/ESA Hubble Space Telescope image features the young star cluster NGC 346. ESA/Hubble & NASA, A. Nota, P. Massey, E. Sabbi, C. Murray, M. Zamani (ESA/Hubble) NGC 346 is in the Small Magellanic Cloud, a satellite galaxy of the Milky Way that lies 200,000 light-years away in the constellation Tucana. The Small Magellanic Cloud is less rich in elements heavier than helium — what astronomers call metals — than the Milky Way. This makes conditions in the galaxy similar to what existed in the early universe.
NGC 346 is home to more than 2,500 newborn stars. The cluster’s most massive stars, which are many times more massive than our Sun, blaze with an intense blue light in this image. The glowing pink nebula and snakelike dark clouds are sculpted by the luminous stars in the cluster.
Hubble’s exquisite sensitivity and resolution were instrumental in uncovering the secrets of NGC 346’s star formation. Using two sets of observations taken 11 years apart, researchers traced the motions of NGC 346’s stars, revealing them to be spiraling in toward the center of the cluster. This spiraling motion arises from a stream of gas from outside of the cluster that fuels star formation in the center of the turbulent cloud.
The inhabitants of this cluster are stellar sculptors, carving out a bubble within the nebula. NGC 346’s hot, massive stars produce intense radiation and fierce stellar winds that pummel the billowing gas of their birthplace, dispersing the surrounding nebula.
The nebula, named N66, is the brightest example of an H II (pronounced ‘H-two’) region in the Small Magellanic Cloud. H II regions are set aglow by ultraviolet light from hot, young stars like those in NGC 346. The presence of this nebula indicates the young age of the star cluster, as an H II region shines only as long as the stars that power it — a mere few million years for the massive stars pictured here.
The Hubble Space Telescope has been operating for over three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope and mission operations. Lockheed Martin Space, based in Denver, also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.
Facebook logo @NASAHubble @NASAHubble Instagram logo @NASAHubble Explore Hubble NGC 346 Images and Science
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NASA’s Hubble Finds Spiraling Stars, Providing Window into Early Universe
Young Stars Sculpt Gas with Powerful Outflows in the Small Magellanic Cloud
Hubble’s Black and White View
Infant Stars in the Small Magellanic Cloud
Hubble Captures Unique Ultraviolet View of a Spectacular Star Cluster
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Last Updated Apr 04, 2025 EditorAndrea GianopoulosLocationNASA Goddard Space Flight Center Contact Media
Claire Andreoli
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
claire.andreoli@nasa.gov
Bethany Downer
ESA/Hubble Chief Science Communications Officer
bethany.downer@esahubble.org
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By European Space Agency
Image: This new image from the NASA/ESA Hubble Space Telescope showcases NGC 346, a dazzling young star cluster in the Small Magellanic Cloud. The Small Magellanic Cloud is a satellite galaxy of the Milky Way, located 210 000 light-years away in the constellation Tucana. The Small Magellanic Cloud is less rich in elements heavier than helium — what astronomers call metals — than the Milky Way. This makes conditions in the galaxy similar to what existed in the early Universe.
Although several images of NGC 346 have been released previously, this view includes new data and is the first to combine Hubble observations made at infrared, optical, and ultraviolet wavelengths into an intricately detailed view of this vibrant star-forming factory.
NGC 346 is home to more than 2500 newborn stars. The cluster’s most massive stars, which are many times more massive than our Sun, blaze with an intense blue light in this image. The glowing pink nebula and snakelike dark clouds are the remnant of the birthplace of the stars in the cluster.
The inhabitants of this cluster are stellar sculptors, carving out a bubble from the nebula. NGC 346’s hot, massive stars produce intense radiation and fierce stellar winds that pummel the billowing gas of their birthplace and begin to disperse the surrounding nebula.
The nebula, named N66, is the brightest example of an H II (pronounced ‘H-two’) region in the Small Magellanic Cloud. H II regions are set aglow by ultraviolet light from hot young stars like those in NGC 346. The presence of the brilliant nebula indicates the young age of the star cluster, as an H II region shines only as long as the stars that power it — a mere few million years for the massive stars pictured here.
[Image description: A star cluster within a nebula. The background is filled with thin, pale blue clouds. Parts are thicker and pinker in colour. The cluster is made up of bright blue stars that illuminate the nebula around them. Large arcs of dense dust curve around, before and behind the clustered stars, pressed together by the stars’ radiation. Behind the clouds of the nebula can be seen large numbers of orange stars.]
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By NASA
X-ray: NASA/CXC/Penn State Univ./L. Townsley et al.; Infrared: NASA/JPL-CalTech/SST; Optical: NASA/STScI/HST; Radio: ESO/NAOJ/NRAO/ALMA; Image Processing: NASA/CXC/SAO/J. Schmidt, N. Wolk, K. Arcand This image, released on Feb. 12, 2025, is the deepest X-ray image ever made of the spectacular star forming region called 30 Doradus. By combining X-ray data from NASA’s Chandra X-ray Observatory (blue and green) with optical data from NASA’s Hubble Space Telescope (yellow) and radio data from the Atacama Large Millimeter/submillimeter Array (orange), this stellar arrangement comes alive.
Otherwise known as the Tarantula Nebula, 30 Dor is located about 160,000 light-years away in a small neighboring galaxy to the Milky Way known as the Large Magellanic Cloud. Because it one of the brightest and populated star-forming regions to Earth, 30 Dor is a frequent target for scientists trying to learn more about how stars are born.
Learn more about this new image and what it reveals.
Image credit: X-ray: NASA/CXC/Penn State Univ./L. Townsley et al.; Infrared: NASA/JPL-CalTech/SST; Optical: NASA/STScI/HST; Radio: ESO/NAOJ/NRAO/ALMA; Image Processing: NASA/CXC/SAO/J. Schmidt, N. Wolk, K. Arcand
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