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By NASA
5 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
The blazar BL Lacertae, a supermassive black hole surrounded by a bright disk and jets oriented toward Earth, provided scientists with a unique opportunity to answer a longstanding question: How are X-rays generated in extreme environments like this?
NASA’s IXPE (Imaging X-ray Polarimetry Explorer) collaborated with radio and optical telescopes to find answers. The results (preprint available here), to be published in the journal Astrophysical Journal Letters, show that interactions between fast-moving electrons and particles of light, called photons, must lead to this X-ray emission.
This artist’s concept depicts the central region of the blazar BL Lacertae, a supermassive black hole surrounded by a bright disk and a jet oriented toward Earth. The galaxy’s central black hole is surrounded by swirls of orange in various shades representing the accretion disk of material falling toward the black hole. While black holes are known for pulling in material, this accretion process can result in the ejection of jets of electrons at nearly the speed of light. The jet of matter is represented by the cone of light that starts at the center of the black hole and widens out as it reaches the bottom of the image. It is streaked with lines of white, pink and purple which represent helix-shaped magnetic fields. We can observe these jets in many wavelengths of light including radio, optical, and X-ray. NASA’s Imaging X-ray Polarimetry Explorer (IXPE) recently collaborated with radio and optical telescopes to observe this jet and determine how the X-rays are generated in these types of celestial environments.NASA/Pablo Garcia Scientists had two competing possible explanations for the X-rays, one involving protons and one involving electrons. Each of these mechanisms would have a different signature in the polarization of X-ray light. Polarization is a property of light that describes the average direction of the electromagnetic waves that make up light.
If the X-rays in a black hole’s jets are highly polarized, that would mean that the X-rays are produced by protons gyrating in the magnetic field of the jet or protons interacting with jet’s photons. If the X-rays have a lower polarization degree, it would suggest that electron-photons interactions lead to X-ray production.
IXPE, which launched Dec. 9, 2021, is the only satellite flying today that can make such a polarization measurement.
“This was one of the biggest mysteries about supermassive black hole jets” said Iván Agudo, lead author of the study and astronomer at the Instituto de Astrofísica de Andalucía – CSIC in Spain. “And IXPE, with the help of a number of supporting ground-based telescopes, finally provided us with the tools to solve it.”
Astronomers found that electrons must be the culprits through a process called Compton Scattering. Compton scattering (or the Compton effect) happens when a photon loses or gains energy after interacting with a charged particle, usually an electron. Within jets from supermassive black holes, electrons move near the speed of light. IXPE helped scientists learn that, in the case of a blazar jet, the electrons have enough energy to scatter photons of infrared light up to X-ray wavelengths.
BL Lacertae (BL Lac for short) is one of the first blazars ever discovered, originally thought to be a variable star in the Lacerta constellation. IXPE observed BL Lac at the end of November 2023 for seven days along with several ground-based telescopes measuring optical and radio polarization at the same time. While IXPE observed BL Lac in the past, this observation was special. Coincidentally, during the X-ray polarization observations, the optical polarization of BL Lac reached a high number: 47.5%.
“This was not only the most polarized BL Lac has been in the past 30 years, this is the most polarized any blazar has ever been observed!” said Ioannis Liodakis, one of the primary authors of the study and astrophysicist at the Institute of Astrophysics – FORTH in Greece.
IXPE found the X-rays were far less polarized than the optical light. The team was not able to measure a strong polarization signal and determined that the X-rays cannot be more polarized than 7.6%. This proved that electrons interacting with photons, via the Compton effect, must explain the X-rays.
The fact that optical polarization was so much higher than in the X-rays can only be explained by Compton scattering.
Steven Ehlert
Project Scientist for IXPE at Marshall Space Flight Center
“The fact that optical polarization was so much higher than in the X-rays can only be explained by Compton scattering”, said Steven Ehlert, project scientist for IXPE and astronomer at the Marshall Space Flight Center.
“IXPE has managed to solve another black hole mystery” said Enrico Costa, astrophysicist in Rome at the Istituto di Astrofísica e Planetologia Spaziali of the Istituto Nazionale di Astrofísica. Costa is one of the scientists who conceived this experiment and proposed it to NASA 10 years ago, under the leadership of Martin Weisskopf, IXPE’s first principal investigator. “IXPE’s polarized X-ray vision has solved several long lasting mysteries, and this is one of the most important. In some other cases, IXPE results have challenged consolidated opinions and opened new enigmas, but this is how science works and, for sure, IXPE is doing very good science.”
What’s next for the blazar research?
“One thing we’ll want to do is try to find as many of these as possible,” Ehlert said. “Blazars change quite a bit with time and are full of surprises.”
More about IXPE
IXPE, which continues to provide unprecedented data enabling groundbreaking discoveries about celestial objects across the universe, is a joint NASA and Italian Space Agency mission with partners and science collaborators in 12 countries. IXPE is led by NASA’s Marshall Space Flight Center in Huntsville, Alabama. BAE Systems, Inc., headquartered in Falls Church, Virginia, manages spacecraft operations together with the University of Colorado’s Laboratory for Atmospheric and Space Physics in Boulder. Learn more about IXPE’s ongoing mission here:
https://www.nasa.gov/ixpe
Elizabeth Landau
NASA Headquarters
elizabeth.r.landau@nasa.gov
202-358-0845
Lane Figueroa
Marshall Space Flight Center, Huntsville, Ala.
lane.e.figueroa@nasa.gov
256.544.0034
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Last Updated May 06, 2025 EditorBeth RidgewayContactElizabeth R. Landauelizabeth.r.landau@nasa.govLocationMarshall Space Flight Center Related Terms
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Black Holes
Black Holes Black holes are among the most mysterious cosmic objects, much studied but not fully understood. These objects aren’t…
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By NASA
NASA The instrument enclosure of NASA’s Near-Earth Object Surveyor is prepared for critical environmental tests inside the historic Chamber A at the Space Environment Simulation Laboratory at NASA’s Johnson Space Center in Houston in December 2024. Wrapped in silver thermal blanketing, the 12-foot-long (3.7-meter-long) angular structure was subjected to the frigid, airless conditions that the spacecraft will experience when in deep space. The cavernous thermal-vacuum test facility is famous for testing the Apollo spacecraft that traveled to the Moon in the 1960s and ’70s.
The instrument enclosure is designed to protect the spacecraft’s infrared telescope while also removing heat from it during operations. After environmental testing was completed, the enclosure returned to NASA’s Jet Propulsion Laboratory in Southern California for further work, after which it will ship to the Space Dynamics Laboratory (SDL) in Logan, Utah, and be joined to the telescope. Both the instrument enclosure and telescope were assembled at JPL.
As NASA’s first space-based detection mission specifically designed for planetary defense, NEO Surveyor will seek out, measure, and characterize the hardest-to-find asteroids and comets that might pose a hazard to Earth. While many near-Earth objects don’t reflect much visible light, they glow brightly in infrared light due to heating by the Sun. The spacecraft’s telescope, which has an aperture of nearly 20 inches (50 centimeters), features detectors sensitive to two infrared wavelengths in which near-Earth objects re-radiate solar heat.
More information about NEO Surveyor is available at: https://science.nasa.gov/mission/neo-surveyor/
Image credit: NASA
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By NASA
For more than a decade, Tristan McKnight has been a driving force behind some of NASA’s most iconic events, orchestrating the behind-the-scenes magic that brings each historic moment to life while sharing the agency’s advancements with the public.
As a multimedia producer on the audiovisual team at Johnson Space Center in Houston, McKnight produces and directs live broadcasts and manages event planning, coordination, and execution. From overseeing resources, mitigating risks, and communicating with stakeholders, he ensures every detail aligns seamlessly.
Official portrait of Tristan McKnight.NASA/Josh Valcarcel McKnight has played an integral role in the audiovisual team’s coverage of major events including the Artemis II crew announcement, where NASA revealed the astronauts who will venture around the Moon and back, to Johnson’s 2023 Open House, which celebrated the agency’s 65th anniversary and the 25th anniversary of the International Space Station’s operations. These achievements highlight key milestones in human space exploration.
A standout achievement was contributing to the Dorothy Vaughan Center in Honor of the Women of Apollo naming ceremony, held on the eve of the 55th anniversary of the Apollo 11 Moon landing. The event honored the unsung heroes who made humanity’s first steps on the Moon possible.
The team’s dedication and passion are a testament to their commitment to sharing NASA’s legacy with the world.
“Not only have these events been impactful to Johnson, but they have also resonated across the entire agency,” McKnight said. “That is what I’m most proud of!”
Tristan McKnight at the 45th Annual Original Martin Luther King Jr. Day Parade in downtown Houston.NASA/James Blair One of McKnight’s most memorable events was the 2023 “Back in the Saddle,” an annual tradition designed to refocus Johnson’s workforce at the start of a new year and renew the center’s commitment to safety and mission excellence. McKnight recalled how the speaker transformed Johnson’s Teague Auditorium into a venue filled with drum kits, inspiring messages, and lighting displays. Each audience member, drumsticks in hand, participated in a lesson on teamwork and synchronization to create a metaphor for working in harmony toward a shared goal.
Like many high-achieving professionals. McKnight has faced moments of self-doubt. Then he realized that he is exactly where he is supposed to be. “As I settled into my role, I recognized that my contributions matter and simply being true to who I am adds value to the Johnson community,” he said.
Tristan McKnight (right) receives a Group Special Act Award from Johnson Space Center Director Vanessa Wyche for his contributions to the Dorothy Vaughn in Honor of the Women of Apollo naming ceremony.NASA Each day brings its own set of challenges, ranging from minor issues like communication gaps and scheduling conflicts to major obstacles like technology failures. One of McKnight’s most valuable lessons is recognizing that there is no one-size-fits-all solution, and each situation requires a thoughtful analysis.
McKnight understands the importance of the “check-and double-check,” a philosophy he considers crucial when working with technology. “Taking the extra time to do your due diligence, or even having someone else take a look, can make all the difference,” he said.
“The challenges I’ve faced helped me grow as a problem solver and taught me valuable lessons on resilience and adaptability in the workplace,” he said. McKnight approaches obstacles with a level head, focusing on effective solutions rather than dwelling on the problem.
Tristan McKnight (left) with his daughter Lydia McKnight and Johnson’s External Relations Director Arturo Sanchez at the 2024 Bring Your Youth To Work Day. NASA/Helen Arase Vargas As humanity looks to the stars, McKnight is energized about the future of exploration, particularly advancements in spacesuit and rocket technology that will enable us to travel farther, faster, and safer than ever before. His work, though grounded on Earth, helps create the inspiration that fuels these bold endeavors.
“My hope for the next generation is that they dive deeper into their curiosity—exploring not only the world around them but also the Moon, planets, and beyond,” he said. “I also hope they carry forward the spirit of resilience and a commitment to making the world a better place for all.”
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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 Explore the Night Sky Observatory Hubble Observatory Hubble Design Mission Operations Missions to Hubble Hubble vs Webb Team Hubble Team Career Aspirations Hubble Astronauts News Hubble News Hubble News Archive Social Media Media Resources Multimedia Multimedia Images Videos Sonifications Podcasts e-Books Online Activities Lithographs Fact Sheets Posters Hubble on the NASA App Glossary More 35th Anniversary Online Activities Hubble captured this image of supernova SN 2022abvt (the pinkish-white dot at image center) about two months after it was discovered in 2022. ESA/Hubble & NASA, R. J. Foley (UC Santa Cruz)
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A supernova and its host galaxy are the subject of this NASA/ESA Hubble Space Telescope image. The galaxy in question is LEDA 132905 in the constellation Sculptor. Even at more than 400 million light-years away, LEDA 132905’s spiral structure is faintly visible, as are patches of bright blue stars.
The bright pinkish-white dot in the center of the image, between the bright center of the galaxy and its faint left edge, is a supernova named SN 2022abvt. Discovered in late 2022, Hubble observed SN 2022abvt about two months later. This image uses data from a study of Type Ia supernovae, which occur when the exposed core of a dead star ignites in a sudden, destructive burst of nuclear fusion. Researchers are interested in this type of supernova because they can use them to measure precise distances to other galaxies.
The universe is a big place, and supernova explosions are fleeting. How is it possible to be in the right place at the right time to catch a supernova when it happens? Today, robotic telescopes that continuously scan the night sky discover most supernovae. The Asteroid Terrestrial-impact Last Alert System, or ATLAS, spotted SN 2022abvt. As the name suggests, ATLAS tracks down the faint, fast-moving signals from asteroids close to Earth. In addition to searching out asteroids, ATLAS also keeps tabs on objects that brighten or fade suddenly, like supernovae, variable stars, and galactic centers powered by hungry black holes.
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Media Contact:
Claire Andreoli (claire.andreoli@nasa.gov)
NASA’s Goddard Space Flight Center, Greenbelt, MD
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Last Updated Feb 07, 2025 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center Related Terms
Hubble Space Telescope Galaxies Goddard Space Flight Center Spiral Galaxies Stars Supernovae The Universe Keep Exploring Discover More Topics From Hubble
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