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Astronomers Watch Delayed Broadcast of a Powerful Stellar Eruption
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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.
NASA’s Goddard Space Flight Center
Download images and videos through NASA’s Scientific Visualization Studio.
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 European Space Agency
Europe’s first MetOp Second Generation, MetOp-SG-A1, weather satellite – which hosts Copernicus Sentinel-5 as part of its instrument package – is set for liftoff on an Ariane 6 rocket from Europe’s Spaceport in Kourou, French Guiana, on 13 August 2025 at 02:37 CEST (12 August 21:37 Kourou time).
Watch live on ESA Web TV One.
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By European Space Agency
With launch slated for August, the first MetOp Second Generation satellite, MetOp-SG-A1, which also carries the Copernicus Sentinel-5 mission, is currently undergoing final preparations for liftoff aboard an Ariane 6 rocket from Europe’s Spaceport in French Guiana.
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By NASA
6 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
Information provided by the NASA-ISRO Synthetic Aperture Radar mission (NISAR) will help to protect and inform communities around the world. The data will aid in managing agricultural fields, monitoring volcanoes, and tracking land-based ice including glaciers.NASA/JPL-Caltech Data from NISAR will map changes to Earth’s surface, helping improve crop management, natural hazard monitoring, and tracking of sea ice and glaciers.
A new U.S.-India satellite called NISAR (NASA-ISRO Synthetic Aperture Radar) will provide high-resolution data enabling scientists to comprehensively monitor the planet’s land and ice surfaces like never before, building a detailed record of how they shift over time. Hailed as a critical part of a pioneering year for U.S.-India civil space cooperation by President Trump and Prime Minister Modi during their visit in Washington in February, the NISAR launch will advance U.S.-India cooperation and benefit the U.S. in the areas of disaster response and agriculture.
As the first joint satellite mission between NASA and the Indian Space Research Organisation (ISRO), NISAR marks a new chapter in the growing collaboration between the two space agencies. Years in the making, the launch of NISAR builds on a strong heritage of successful programs, including Chandrayaan-1 and the recent Axiom Mission 4, which saw ISRO and NASA astronauts living and working together aboard the International Space Station for the first time.
The information NISAR provides will help decision-makers, communities, and scientists monitor agricultural fields, refine understanding of natural hazards such as landslides and earthquakes, and help teams prepare for and respond to disasters like hurricanes, floods, and volcanic eruptions. The satellite will also provide key global observations of changes to ice sheets, glaciers, and permafrost, as well as forests and wetlands.
The NISAR mission is slated to launch no earlier than July 30 from Satish Dhawan Space Centre on India’s southeastern coast aboard an ISRO Geosynchronous Satellite Launch Vehicle.
Here are five things to know about NISAR:
1. The NISAR satellite will provide a 3D view of Earth’s land and ice.
Two synthetic aperture radars (SARs) aboard NISAR will detect changes in the planet’s surface down to fractions of an inch. The spacecraft will bounce microwave signals off Earth’s surface and receive the return signals on a radar antenna reflector measuring 39 feet (12 meters) across. The satellite’s ability to “see” through clouds and light rain, day and night, will enable data users to continuously monitor earthquake- and landslide-prone areas and determine how quickly glaciers and ice sheets are changing. It also will offer unprecedented coverage of Antarctica, information that will help with studying how the continent’s ice sheet changes over time.
2. Data from NISAR will provide critical insights to help governments and decision-makers plan for natural and human-caused hazards.
Earthquakes, volcanoes, and aging infrastructure can pose risks to lives and property. Able to see subtle changes in Earth’s surface, NISAR can help with hazard-monitoring efforts and potentially give decision-makers more time to prepare for a possible disaster. For earthquakes, NISAR will provide insights into which parts of a fault slowly move without producing quakes and which are locked together and could potentially slip. The satellite will be able to monitor the area around thousands of volcanoes, detecting land movement that could be a precursor to an eruption. When it comes to infrastructure such as levees, aqueducts, and dams, NISAR data collected over time can help managers detect if nearby land motion could jeopardize key structures, and then assess the integrity of those facilities.
3. The most advanced radar system ever launched as part of a NASA or ISRO mission, NISAR will generate more data on a daily basis than any previous Earth satellite from either agency.
About the length of a pickup truck, NISAR’s main body contains a dual-radar payload — an L-band system with a 10-inch (25-centimeter) wavelength and an S-band system with a 4-inch (10-centimeter) wavelength. Each system is sensitive to land and ice features of different sizes and specializes in detecting certain attributes, such as moisture content, surface roughness, and motion. By including both radars on one spacecraft — a first — NISAR will be more capable than previous SAR missions. These two radars, one from NASA and one from ISRO, and the data they will produce, exemplify how collaboration between spacefaring allies can achieve more than either would alone.
NISAR press kit The radars will generate about 80 terabytes of data products per day over the course of NISAR’s prime mission. That’s roughly enough data to fill about 150 512-gigabyte hard drives each day. The information will be processed, stored, and distributed via the cloud — and accessible to all.
This artist’s concept depicts the NISAR satellite in orbit over central and Northern California. The spacecraft will survey all of Earth’s land and ice-covered surfaces twice every 12 days.NASA/JPL-Caltech 4. The NISAR mission will help monitor ecosystems around the world.
The mission’s two radars will monitor Earth’s land and ice-covered surfaces twice every 12 days. Their near-comprehensive coverage will include areas not previously covered by other Earth-observing radar satellites with such frequency. The NISAR satellite’s L-band radar penetrates deep into forest canopies, providing insights into forest structure, while the S-band radar is ideal for monitoring crops. The NISAR data will help researchers assess how forests, wetlands, agricultural areas, and permafrost change over time.
5. The NISAR mission marks the first collaboration between NASA and ISRO on a project of this scale and marks the next step in a long line of Earth-observing SAR missions.
The NISAR satellite features components developed on opposite sides of the planet by engineers from ISRO and NASA’s Jet Propulsion Laboratory working together. The S-band radar was built at ISRO’s Space Applications Centre in Ahmedabad, while JPL built the L-band radar in Southern California. After engineers from JPL and ISRO integrated NISAR’s instruments with a modified ISRO I3K spacecraft bus and tested the satellite, ISRO transported NISAR to Satish Dhawan Space Centre in May 2025 to prepare it for launch.
The SAR technique was invented in the U.S. in 1952 and now countries around the globe have SAR satellites for a variety of missions. NASA first used the technique with a space-based satellite in 1978 on the ocean-observing Seasat, which included the first spaceborne SAR instrument for scientific observations. In 2012, ISRO began launching SAR missions starting with Radar Imaging Satellite (RISAT-1), followed by RISAT-1A in 2022, to support a wide range of applications in India.
More About NISAR
Managed by Caltech in Pasadena, JPL leads the U.S. component of the project and provided the L-band SAR. JPL also provided the radar reflector antenna, the deployable boom, a high-rate communication subsystem for science data, GPS receivers, a solid-state recorder, and payload data subsystem. NASA’s Goddard Space Flight Center manages the Near Space Network, which will receive NISAR’s L-band data.
The ISRO Space Applications Centre is providing the mission’s S-band SAR. The U R Rao Satellite Centre is providing the spacecraft bus. The rocket is from Vikram Sarabhai Space Centre, launch services are through Satish Dhawan Space Centre, and satellite mission operations are by the ISRO Telemetry Tracking and Command Network. The National Remote Sensing Centre is responsible for S-band data reception, operational products generation, and dissemination.
To learn more about NISAR, visit:
https://nisar.jpl.nasa.gov/
How New NASA, India Satellite NISAR Will See Earth Powerful New US-Indian Satellite Will Track Earth’s Changing Surface NASA-ISRO Radar Mission to Provide Dynamic View of Forests, Wetlands NASA-ISRO Mission Will Map Farmland From Planting to Harvest News Media Contacts
Andrew Wang / Jane J. Lee
Jet Propulsion Laboratory, Pasadena, Calif.
626-379-6874 / 626-491-1943
andrew.wang@jpl.nasa.gov / jane.j.lee@jpl.nasa.gov
2025-090
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Last Updated Jul 21, 2025 Related Terms
NISAR (NASA-ISRO Synthetic Aperture Radar) Earth Science Earth Surface & Interior Jet Propulsion Laboratory Explore More
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