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By European Space Agency
Image: The Ocean and Land Colour Instrument on Copernicus Sentinel-3 captured this image of Earth’s biggest iceberg, A23a, on 5 April 2025. View the full article
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By NASA
Did you know some of the brightest sources of light in the sky come from the regions around black holes in the centers of galaxies? It sounds a little contradictory, but it’s true! They may not look bright to our eyes, but satellites have spotted oodles of them across the universe.
One of those satellites is NASA’s Fermi Gamma-ray Space Telescope. Fermi has found thousands of these kinds of galaxies since it launched in 2008, and there are many more out there!
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Watch a cosmic gamma-ray fireworks show in this animation using just a year of data from the Large Area Telescope (LAT) aboard NASA’s Fermi Gamma-ray Space Telescope. Each object’s magenta circle grows as it brightens and shrinks as it dims. The yellow circle represents the Sun following its apparent annual path across the sky. The animation shows a subset of the LAT gamma-ray records available for more than 1,500 objects in a continually updated repository. Over 90% of these sources are a type of galaxy called a blazar, powered by the activity of a supermassive black hole. NASA’s Marshall Space Flight Center/Daniel Kocevski Black holes are regions of space that have so much gravity that nothing — not light, not particles, nada — can escape. Most galaxies have supermassive black holes at their centers, and these black holes are hundreds of thousands to billions of times the mass of our Sun. In active galactic nuclei (also called “AGN” for short, or just “active galaxies”) the central region is stuffed with gas and dust that’s constantly falling toward the black hole. As the gas and dust fall, they start to spin and form a disk. Because of the friction and other forces at work, the spinning disk starts to heat up.
This composite view of the active galaxy Markarian 573 combines X-ray data (blue) from NASA’s Chandra X-ray Observatory and radio observations (purple) from the Karl G. Jansky Very Large Array in New Mexico with a visible light image (gold) from the Hubble Space Telescope. Markarian 573 is an active galaxy that has two cones of emission streaming away from the supermassive black hole at its center. X-ray: NASA/CXC/SAO/A.Paggi et al; Optical: NASA/STScI; Radio: NSF/NRAO/VLA The disk’s heat gets emitted as light, but not just wavelengths of it that we can see with our eyes. We detect light from AGN across the entire electromagnetic spectrum, from the more familiar radio and optical waves through to the more exotic X-rays and gamma rays, which we need special telescopes to spot.
In the heart of an active galaxy, matter falling toward a supermassive black hole creates jets of particles traveling near the speed of light as shown in this artist’s concept. NASA/Goddard Space Flight Center Conceptual Image Lab About one in 10 AGN beam out jets of energetic particles, which are traveling almost as fast as light. Scientists are studying these jets to try to understand how black holes — which pull everything in with their huge amounts of gravity — somehow provide the energy needed to propel the particles in these jets.
This artist’s concept shows two views of the active galaxy TXS 0128+554, located around 500 million light-years away. Left: The galaxy’s central jets appear as they would if we viewed them both at the same angle. The black hole, embedded in a disk of dust and gas, launches a pair of particle jets traveling at nearly the speed of light. Scientists think gamma rays (magenta) detected by NASA’s Fermi Gamma-ray Space Telescope originate from the base of these jets. As the jets collide with material surrounding the galaxy, they form identical lobes seen at radio wavelengths (orange). The jets experienced two distinct bouts of activity, which created the gap between the lobes and the black hole. Right: The galaxy appears in its actual orientation, with its jets tipped out of our line of sight by about 50 degrees. NASA’s Goddard Space Flight Center Many of the ways we tell one type of AGN from another depend on how they’re oriented from our point of view. With radio galaxies, for example, we see the jets from the side as they’re beaming vast amounts of energy into space. Then there’s blazars, which are a type of AGN that have a jet that is pointed almost directly at Earth, which makes the AGN particularly bright.
Blazar 3C 279’s historic gamma-ray flare in 2015 can be seen in this image from the Large Area Telescope on NASA’s Fermi satellite. During the flare, the blazar outshone the Vela pulsar, usually the brightest object in the gamma-ray sky. NASA/DOE/Fermi LAT Collaboration Fermi has been searching the sky for gamma ray sources since 2008. More than half of the sources it has found have been blazars. Gamma rays are useful because they can tell us a lot about how particles accelerate and how they interact with their environment.
So why do we care about AGN? We know that some AGN formed early in the history of the universe. With their enormous power, they almost certainly affected how the universe changed over time. By discovering how AGN work, we can understand better how the universe came to be the way it is now.
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Last Updated Apr 30, 2025 Related Terms
The Universe Active Galaxies Fermi Gamma-Ray Space Telescope Galaxies Explore More
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By NASA
1 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
On April 16, 2025, the Earth Science Division at NASA’s Ames Research Center in Silicon Valley held an Earth Science Showcase to share its work with the center and their families. As part of this event, kids were invited to share something they like about the Earth. These are their masterpieces.
Sora U. Age 9. “Wildlife”
Sora U. Age 9. “Wildlife” Wesley P. Age 2.5. “Pale Blue”
Wesley P. Age 2.5. “Pale Blue” Kira U. Age 5. “Hawaii”
Kira U. Age 5. “Hawaii” Anonymous. “eARTh”
Anonymous. “eARTh” Brooks P. Age 8mo. “Squiggles”
Brooks P. Age 8mo. “Squiggles” About the Author
Milan Loiacono
Science Communication SpecialistMilan Loiacono is a science communication specialist for the Earth Science Division at NASA Ames Research Center.
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Last Updated Apr 25, 2025 Related Terms
Earth Science Ames Research Center Ames Research Center's Science Directorate Earth Science Division Keep Exploring Discover More Topics From NASA
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By European Space Agency
Image: Copernicus Sentinel-1 captured this radar image over French Guiana – home to Europe’s Spaceport in Kourou, where ESA’s Biomass mission is being prepared for liftoff on 29 April onboard a Vega-C rocket. View the full article
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By European Space Agency
Video: 00:02:22 ESA’s state-of-the-art Biomass mission has been designed to shed new light on the health and dynamics of the world’s forests, revealing how they are changing over time and, critically, enhancing our understanding of their role in the global carbon cycle. It is the first satellite to carry a fully polarimetric P-band synthetic aperture radar for interferometric imaging. Thanks to the long wavelength of P-band, around 70 cm, the radar signal can slice through the forest canopy and whole forest layer to measure the ‘biomass’, meaning the woody trunks, branches and stems, which is where trees store most of their carbon.
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