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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 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 2 min read
Hubble Studies a Nearby Galaxy’s Star Formation
This NASA/ESA Hubble Space Telescope image features the picturesque spiral galaxy NGC 4941. ESA/Hubble & NASA, D. Thilker This NASA/ESA Hubble Space Telescope image features the picturesque spiral galaxy NGC 4941, which lies about 67 million light-years from Earth in the constellation Virgo (The Maiden). Because this galaxy is nearby, cosmically speaking, Hubble’s keen instruments are able to pick out exquisite details such as individual star clusters and filamentary clouds of gas and dust.
The data used to construct this image were collected as part of an observing program that investigates the star formation and stellar feedback cycle in nearby galaxies. As stars form in dense, cold clumps of gas, they begin to influence their surroundings. Stars heat and stir up the gas clouds in which they form through winds, starlight, and — eventually, for massive stars — by exploding as supernovae. These processes are collectively called stellar feedback, and they influence the rate at which a galaxy can form new stars.
As it turns out, stars aren’t the only entities providing feedback in NGC 4941. At the heart of this galaxy lies an active galactic nucleus: a supermassive black hole feasting on gas. As the black hole amasses gas from its surroundings, the gas swirls into a superheated disk that glows brightly at wavelengths across the electromagnetic spectrum. Similar to stars — but on a much, much larger scale — active galactic nuclei shape their surroundings through winds, radiation, and powerful jets, altering not only star formation but also the evolution of the galaxy as a whole.
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Claire Andreoli (claire.andreoli@nasa.gov)
NASA’s Goddard Space Flight Center, Greenbelt, MD
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Last Updated Apr 04, 2025 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center Related Terms
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Hubble Space Telescope
Since its 1990 launch, the Hubble Space Telescope has changed our fundamental understanding of the universe.
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By European Space Agency
Image: This image shows Webb’s recent observation of the asteroid 2024 YR4 using both its Near-Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI). Data from NIRCam shows reflected light, while the MIRI observations show thermal light.
On 8 March 2025, the NASA/ESA/CSA James Webb Space Telescope turned its watchful eye toward asteroid 2024 YR4, which we now know poses no significant threat to Earth in 2032 and beyond.
This is the smallest object targeted by Webb to date, and one of the smallest objects to have its size directly measured.
Observations were taken to study the thermal properties of 2024 YR4, including how quickly it heats up and cools down and how hot it is at its current distance from the Sun. These measurements indicate that this asteroid does not share properties observed in larger asteroids. This is likely a combination of its fast spin and lack of fine-grained sand on its surface. Further research is needed, however this is considered consistent with a surface dominated by rocks that are roughly fist-sized or larger.
Asteroid 2024 YR4 was recently under close watch by the team at ESA's Near Earth Objects Coordination Centre, located in Italy. Planetary defence experts from the Agency's Space Safety programme worked with NASA and the international asteroid community to closely watch this object and refine its orbit, which was eventually determined to not pose a risk of Earth impact. Read details on this unusual campaign via ESA's Rocket Science blog and in news articles here and here.
Webb’s observations indicate that the asteroid measures roughly 60 meters (comparable to the height of a 15-story building).
The new observations from Webb not only provide unique information about 2024 YR4’s size, but can also complement ground-based observations of the object's position to help improve our understanding of the object’s orbit and future trajectory.
Note: This post highlights data from Webb science in progress, which has not yet been through the peer-review process.
[Image description: A collage of three images showing the black expanse of space. Two-thirds of the collage is taken up by the black background sprinkled with small, blurry galaxies in orange, blue, and white. There are two images in a column at the right side of the collage. On the right side of the main image, not far from the top, a very faint dot is outlined with a white square. At the right, there are two zoomed in views of this area. The top box is labeled NIRCam and shows a fuzzy dot at the center of the inset. The bottom box is labeled MIRI and shows a fuzzy pinkish dot.]
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By NASA
Explore This Section Webb News Latest News Latest Images Blog (offsite) Awards X (offsite – login reqd) Instagram (offsite – login reqd) Facebook (offsite- login reqd) Youtube (offsite) Overview About Who is James Webb? Fact Sheet Impacts+Benefits FAQ Science Overview and Goals Early Universe Galaxies Over Time Star Lifecycle Other Worlds Observatory Overview Launch Deployment Orbit Mirrors Sunshield Instrument: NIRCam Instrument: MIRI Instrument: NIRSpec Instrument: FGS/NIRISS Optical Telescope Element Backplane Spacecraft Bus Instrument Module Multimedia About Webb Images Images Videos What is Webb Observing? 3d Webb in 3d Solar System Podcasts Webb Image Sonifications Team International Team People Of Webb More For the Media For Scientists For Educators For Fun/Learning 5 Min Read NASA Webb Explores Effect of Strong Magnetic Fields on Star Formation
An image of the Milky Way captured by the MeerKAT radio telescope array puts the James Webb Space Telescope’s image of the Sagittarius C region in context. Full image below. Credits:
NASA, ESA, CSA, STScI, SARAO, Samuel Crowe (UVA), John Bally (CU), Ruben Fedriani (IAA-CSIC), Ian Heywood (Oxford) Follow-up research on a 2023 image of the Sagittarius C stellar nursery in the heart of our Milky Way galaxy, captured by NASA’s James Webb Space Telescope, has revealed ejections from still-forming protostars and insights into the impact of strong magnetic fields on interstellar gas and the life cycle of stars.
“A big question in the Central Molecular Zone of our galaxy has been, if there is so much dense gas and cosmic dust here, and we know that stars form in such clouds, why are so few stars born here?” said astrophysicist John Bally of the University of Colorado Boulder, one of the principal investigators. “Now, for the first time, we are seeing directly that strong magnetic fields may play an important role in suppressing star formation, even at small scales.”
Detailed study of stars in this crowded, dusty region has been limited, but Webb’s advanced near-infrared instruments have allowed astronomers to see through the clouds to study young stars like never before.
“The extreme environment of the galactic center is a fascinating place to put star formation theories to the test, and the infrared capabilities of NASA’s James Webb Space Telescope provide the opportunity to build on past important observations from ground-based telescopes like ALMA and MeerKAT,” said Samuel Crowe, another principal investigator on the research, a senior undergraduate at the University of Virginia and a 2025 Rhodes Scholar.
Bally and Crowe each led a paper published in The Astrophysical Journal.
Image A: Milky Way Center (MeerKAT and Webb)
An image of the Milky Way captured by the MeerKAT (formerly the Karoo Array Telescope) radio telescope array puts the James Webb Space Telescope’s image of the Sagittarius C region in context. Like a super-long exposure photograph, MeerKAT shows the bubble-like remnants of supernovas that exploded over millennia, capturing the dynamic nature of the Milky Way’s chaotic core. At the center of the MeerKAT image the region surrounding the Milky Way’s supermassive black hole blazes bright. Huge vertical filamentary structures echo those captured on a smaller scale by Webb in Sagittarius C’s blue-green hydrogen cloud. NASA, ESA, CSA, STScI, SARAO, Samuel Crowe (UVA), John Bally (CU), Ruben Fedriani (IAA-CSIC), Ian Heywood (Oxford) Image B: Milky Way Center (MeerKAT and Webb), Labeled
The star-forming region Sagittarius C, captured by the James Webb Space Telescope, is about 200 light-years from the Milky Way’s central supermassive black hole, Sagittarius A*. The spectral index at the lower left shows how color was assigned to the radio data to create the image. On the negative end, there is non-thermal emission, stimulated by electrons spiraling around magnetic field lines. On the positive side, thermal emission is coming from hot, ionized plasma. For Webb, color is assigned by shifting the infrared spectrum to visible light colors. The shortest infrared wavelengths are bluer, and the longer wavelengths appear more red. NASA, ESA, CSA, STScI, SARAO, Samuel Crowe (UVA), John Bally (CU), Ruben Fedriani (IAA-CSIC), Ian Heywood (Oxford) Using Infrared to Reveal Forming Stars
In Sagittarius C’s brightest cluster, the researchers confirmed the tentative finding from the Atacama Large Millimeter Array (ALMA) that two massive stars are forming there. Along with infrared data from NASA’s retired Spitzer Space Telescope and SOFIA (Stratospheric Observatory for Infrared Astronomy) mission, as well as the Herschel Space Observatory, they used Webb to determine that each of the massive protostars is already more than 20 times the mass of the Sun. Webb also revealed the bright outflows powered by each protostar.
Even more challenging is finding low-mass protostars, still shrouded in cocoons of cosmic dust. Researchers compared Webb’s data with ALMA’s past observations to identify five likely low-mass protostar candidates.
The team also identified 88 features that appear to be shocked hydrogen gas, where material being blasted out in jets from young stars impacts the surrounding gas cloud. Analysis of these features led to the discovery of a new star-forming cloud, distinct from the main Sagittarius C cloud, hosting at least two protostars powering their own jets.
“Outflows from forming stars in Sagittarius C have been hinted at in past observations, but this is the first time we’ve been able to confirm them in infrared light. It’s very exciting to see, because there is still a lot we don’t know about star formation, especially in the Central Molecular Zone, and it’s so important to how the universe works,” said Crowe.
Magnetic Fields and Star Formation
Webb’s 2023 image of Sagittarius C showed dozens of distinctive filaments in a region of hot hydrogen plasma surrounding the main star-forming cloud. New analysis by Bally and his team has led them to hypothesize that the filaments are shaped by magnetic fields, which have also been observed in the past by the ground-based observatories ALMA and MeerKAT (formerly the Karoo Array Telescope).
“The motion of gas swirling in the extreme tidal forces of the Milky Way’s supermassive black hole, Sagittarius A*, can stretch and amplify the surrounding magnetic fields. Those fields, in turn, are shaping the plasma in Sagittarius C,” said Bally.
The researchers think that the magnetic forces in the galactic center may be strong enough to keep the plasma from spreading, instead confining it into the concentrated filaments seen in the Webb image. These strong magnetic fields may also resist the gravity that would typically cause dense clouds of gas and dust to collapse and forge stars, explaining Sagittarius C’s lower-than-expected star formation rate.
“This is an exciting area for future research, as the influence of strong magnetic fields, in the center of our galaxy or other galaxies, on stellar ecology has not been fully considered,” said Crowe.
The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).
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View/Download the science paper led by Bally from the The Astrophysical Journal.
View/Download the science paper led by Crowe from the The Astrophysical Journal.
Media Contacts
Laura Betz – laura.e.betz@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md.
Leah Ramsay – lramsay@stsci.edu
Space Telescope Science Institute, Baltimore, Md.
Christine Pulliam – cpulliam@stsci.edu
Space Telescope Science Institute, Baltimore, Md.
Related Information
Read more: press releases about the center of the Milky Way
NASA’s Universe of Learning: ViewSpace Interactive image tour of the center of the Milky Way
Learn more about the Milky Way and Sagittarius Constellation
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James Webb Space Telescope
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Last Updated Apr 02, 2025 Editor Marty McCoy Contact Laura Betz laura.e.betz@nasa.gov Related Terms
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By NASA
X-ray: NASA/CXC/Technion/N. Keshet et al.; Illustration: NASA/CXC/SAO/M. Weiss People often think about archaeology happening deep in jungles or inside ancient pyramids. However, a team of astronomers has shown that they can use stars and the remains they leave behind to conduct a special kind of archaeology in space.
Mining data from NASA’s Chandra X-ray Observatory, the team of astronomers studied the relics that one star left behind after it exploded. This “supernova archaeology” uncovered important clues about a star that self-destructed – probably more than a million years ago.
Today, the system called GRO J1655-40 contains a black hole with nearly seven times the mass of the Sun and a star with about half as much mass. However, this was not always the case.
Originally GRO J1655-40 had two shining stars. The more massive of the two stars, however, burned through all of its nuclear fuel and then exploded in what astronomers call a supernova. The debris from the destroyed star then rained onto the companion star in orbit around it, as shown in the artist’s concept.
This artist’s impression shows the effects of the collapse and supernova explosion of a massive star. A black hole (right) was formed in the collapse and debris from the supernova explosion is raining down onto a companion star (left), polluting its atmosphere.CXC/SAO/M. Weiss With its outer layers expelled, including some striking its neighbor, the rest of the exploded star collapsed onto itself and formed the black hole that exists today. The separation between the black hole and its companion would have shrunk over time because of energy being lost from the system, mainly through the production of gravitational waves. When the separation became small enough, the black hole, with its strong gravitational pull, began pulling matter from its companion, wrenching back some of the material its exploded parent star originally deposited.
While most of this material sank into the black hole, a small amount of it fell into a disk that orbits around the black hole. Through the effects of powerful magnetic fields and friction in the disk, material is being sent out into interstellar space in the form of powerful winds.
This is where the X-ray archaeological hunt enters the story. Astronomers used Chandra to observe the GRO J1655-40 system in 2005 when it was particularly bright in X-rays. Chandra detected signatures of individual elements found in the black hole’s winds by getting detailed spectra – giving X-ray brightness at different wavelengths – embedded in the X-ray light. Some of these elements are highlighted in the spectrum shown in the inset.
The team of astronomers digging through the Chandra data were able to reconstruct key physical characteristics of the star that exploded from the clues imprinted in the X-ray light by comparing the spectra with computer models of stars that explode as supernovae. They discovered that, based on the amounts of 18 different elements in the wind, the long-gone star destroyed in the supernova was about 25 times the mass of the Sun, and was much richer in elements heavier than helium in comparison with the Sun.
This analysis paves the way for more supernova archaeology studies using other outbursts of double star systems.
A paper describing these results titled “Supernova Archaeology with X-Ray Binary Winds: The Case of GRO J1655−40” was published in The Astrophysical Journal in May 2024. The authors of this study are Noa Keshet (Technion — Israel Institute of Technology), Ehud Behar (Technion), and Timothy Kallman (NASA’s Goddard Space Flight Center).
NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program. The Smithsonian Astrophysical Observatory’s Chandra X-ray Center controls science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.
Read more from NASA’s Chandra X-ray Observatory.
Learn more about the Chandra X-ray Observatory and its mission here:
https://www.nasa.gov/chandra
https://chandra.si.edu
Visual Description
This release features an artist’s rendering of a supernova explosion, inset with a spectrum graph.
The artist’s illustration features a star and a black hole in a system called GRO J1655-40. Here, the black hole is represented by a black sphere to our upper right of center. The star is represented by a bright yellow sphere to our lower left of center. In this illustration, the artist captures the immensely powerful supernova as a black hole is created from the collapse of a massive star, with an intense burst of blurred beams radiating from the black sphere. The blurred beams of red, orange, and yellow light show debris from the supernova streaking across the entire image in rippling waves. These beams rain debris on the bright yellow star.
When astronomers used the Chandra X-ray Observatory to observe the system in 2005, they detected signatures of individual elements embedded in the X-ray light. Some of those elements are highlighted in the spectrum graph shown in the inset, positioned at our upper lefthand corner.
The graph’s vertical axis, on our left, indicates X-ray brightness from 0.0 up to 0.7 in intensity units. The horizontal axis, at the bottom of the graph, indicates Wavelength from 6 to 12 in units of Angstroms. On the graph, a tight zigzagging line begins near the top of the vertical axis, and slopes down toward the far end of the horizontal axis. The sharp dips show wavelengths where the light has been absorbed by different elements, decreasing the X-ray brightness. Some of the elements causing these dips have been labeled, including Silicon, Magnesium, Iron, Nickel, Neon, and Cobalt.
News Media Contact
Megan Watzke
Chandra X-ray Center
Cambridge, Mass.
617-496-7998
mwatzke@cfa.harvard.edu
Lane Figueroa
Marshall Space Flight Center, Huntsville, Alabama
256-544-0034
lane.e.figueroa@nasa.gov
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By European Space Agency
Image: Spying a spiral through a cosmic lens (Webb telescope image) View the full article
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