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Stellar Thief Is the Surviving Companion to a Supernova
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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
Explore Hubble Hubble Home Overview About Hubble The History of Hubble Hubble Timeline Why Have a Telescope in Space? Hubble by the Numbers At the Museum FAQs Impact & Benefits Hubble’s Impact & Benefits Science Impacts Cultural Impact Technology Benefits Impact on Human Spaceflight Astro Community Impacts Science Hubble Science Science Themes Science Highlights Science Behind Discoveries Hubble’s Partners in Science Universe Uncovered Hubble and Artificial Intelligence Explore the Night Sky Observatory Hubble Observatory Hubble Design Mission Operations Missions to Hubble Hubble vs Webb Team Hubble Team Career Aspirations Hubble Astronauts Multimedia Images Videos Sonifications Podcasts e-Books Online Activities 3D Hubble Models Lithographs Fact Sheets Posters Hubble on the NASA App Glossary News Hubble News Social Media Media Resources More 35th Anniversary Online Activities 2 min read
Hubble Surveys Supernova-Rich Spiral
This NASA/ESA Hubble Space Telescope image features the face-on spiral galaxy NGC 1309. ESA/Hubble & NASA, L. Galbany, S. Jha, K. Noll, A. Riess Rich with detail, the spiral galaxy NGC 1309 shines in this NASA/ESA Hubble Space Telescope image. NGC 1309 is about 100 million light-years away in the constellation Eridanus.
This stunning Hubble image encompasses NGC 1309’s bluish stars, dark brown gas clouds, and pearly-white core, as well as hundreds of distant background galaxies. Nearly every smudge, streak, and blob of light in this image is an individual galaxy, some shining through less dense regions of NGC 1309 itself. The only exception to this extragalactic ensemble is a star near the top of the frame identified by its diffraction spikes. The star is positively neighborly at just a few thousand light-years away in the Milky Way galaxy.
Hubble turned its attention toward NGC 1309 several times; previous Hubble images of this galaxy were released in 2006 and 2014. Much of NGC 1309’s scientific interest derives from two supernovae, SN 2002fk in 2002 and SN 2012Z in 2012. SN 2002fk was a perfect example of a Type Ia supernova, which happens when the stripped-down core of a dead star (a white dwarf) explodes.
SN 2012Z, on the other hand, was a bit of a renegade. It was classified as a Type Iax supernova: while its spectrum resembled that of a Type Ia supernova, the explosion wasn’t as bright as expected. Hubble observations showed that in this case, the supernova did not destroy the white dwarf completely, leaving behind a ‘zombie star’ that shone even brighter than it did before the explosion. Hubble observations of NGC 1309 taken across several years also made this the first time astronomers spotted a star system that later produced an unusual supernova explosion of a white dwarf.
Text Credit: ESA/Hubble
Facebook logo @NASAHubble @NASAHubble Instagram logo @NASAHubble Media Contact:
Claire Andreoli (claire.andreoli@nasa.gov)
NASA’s Goddard Space Flight Center, Greenbelt, MD
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Last Updated Jul 31, 2025 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center Related Terms
Astrophysics Astrophysics Division Galaxies Goddard Space Flight Center Hubble Space Telescope Spiral Galaxies The Universe Keep Exploring Discover More Topics From Hubble
Hubble Space Telescope
Since its 1990 launch, the Hubble Space Telescope has changed our fundamental understanding of the universe.
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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
An image of Betelgeuse, the yellow-red star, and the signature of its close companion, the faint blue object.Data: NASA/JPL/NOIRlab. Visualization: NOIRLAB. A century-old hypothesis that Betelgeuse, the 10th brightest star in our night sky, is orbited by a very close companion star was proved true by a team of astrophysicists led by a scientist at NASA’s Ames Research Center in California’s Silicon Valley.
The research published in The Astrophysical Journal Letters in the paper “Probable Direct Imaging Discovery of the Stellar Companion to Betelgeuse.”
Fluctuations in the brightness and measured velocity of Betelgeuse, the closest red supergiant star to Earth, had long presented clues that it may have a partner, but the bigger star’s intense glow made direct observations of any fainter neighbors nearly impossible.
Two recent studies by other teams of astronomers reignited the companion star hypothesis by using more than 100 years of Betelgeuse observations to provide predictions of the companion’s location and brightness.
If the smaller star did exist, the location predictions suggested that scientists had a window of just a few months to observe the companion star at its widest separation from Betelgeuse, as it orbited near the visible edge of the supergiant. After that, they would have to wait another three years for it to orbit to the other side and again leave the overpowering glow of its larger companion.
Searches for the companion were initially made using space-based telescopes, because observing through Earth’s atmosphere can blur images of astronomical objects. But these efforts did not detect the companion.
Steve Howell, a senior research scientist at Ames, recognized the ground-based Gemini North telescope in Hawai’i, one of the largest in the world, paired with a special, high-resolution camera built by NASA, had the potential to directly observe the close companion to Betelgeuse, despite the atmospheric blurring.
Officially called the ‘Alopeke speckle instrument, the advanced imaging camera let them obtain many thousands of short exposures to measure the atmospheric interference in their data and remove it with detailed image processing, providing an image of Betelgeuse and its companion.
Howell’s team detected the very faint companion star right where it was predicted to be, orbiting very close to the outer edge of Betelgeuse.
“I hope our discovery excites other astrophysicists about the robust power of ground-based telescopes and speckle imagers – a key to opening new observational windows,” said Howell. “This can help unlock the great mysteries in our universe.”
To start, this discovery of a close companion to Betelgeuse may explain why other similar red supergiant stars undergo periodic changes in their brightness on the scale of many years.
Howell plans to continue observations of Betelgeuse’s stellar companion to better understand its nature. The companion star will again return to its greatest separation from Betelgeuse in November 2027, a time when it will be easiest to detect.
Having found the long-anticipated companion star, Howell turned to giving it a name. The traditional star name “Betelgeuse” derives from Arabic, meaning “the hand of al-Jawza’,” a female figure in old Arabian legend. Fittingly, Howell’s team named the orbiting companion “Siwarha,” meaning “her bracelet.”
Photo of the constellation Orion, showing the location of Betelgeuse – and its newfound companion star.NOIRLab/Eckhard Slawik The NASA–National Science Foundation Exoplanet Observational Research Program (NN-EXPLORE) is a joint initiative to advance U.S. exoplanet science by providing the community with access to cutting-edge, ground-based observational facilities. Managed by NASA’s Exoplanet Exploration Program, NN-EXPLORE supports and enhances the scientific return of space missions such as Kepler, TESS (Transiting Exoplanet Survey Satellite), Hubble Space Telescope, and James Webb Space Telescope by enabling essential follow-up observations from the ground—creating strong synergies between space-based discoveries and ground-based characterization. NASA’s Exoplanet Exploration Program is located at the agency’s Jet Propulsion Laboratory.
To learn more about NN-EXPLORE, visit:
https://exoplanets.nasa.gov/exep/NNExplore/overview
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Last Updated Jul 23, 2025 Related Terms
Astrophysics Ames Research Center Ames Research Center's Science Directorate Astrophysics Division Exoplanet Exploration Program General Science & Research Science Mission Directorate Explore More
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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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