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Curiosity Blog, Sols 4988-4994: More New Tricks for an Old Dog

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Curiosity Blog, Sols 4988-4994: More New Tricks for an Old Dog

A close-up view of the Martian surface taken by the Curiosity rover. The terrain consists of fine, reddish-brown sand scattered with small rocks. On the center-left, a prominent pebble casts a distinct shadow to the right. In the upper right area, there is a shallow, circular depression in the soil, revealing the slightly rougher texture beneath the top layer of dust. Faint, straight lines or cracks are visible intersecting across the dusty terrain.
NASA’s Mars rover Curiosity acquired this image using its Mars Hand Lens Imager (MAHLI), showing an example of a broad pit that appeared in workspaces this week. The pit diameter is about 1 centimeter (0.39 inches). MAHLI is located on the turret at the end of the rover’s robotic arm, and uses an onboard focusing process to make a composite of images of the same target acquired at different focus positions, in order to make a single image that brings as many features into focus as possible. Curiosity created the composite on Aug. 19, 2026 — Sol 4989, or Martian day 4,989 of the Mars Science Laboratory mission — at 07:59:21 UTC.
NASA/JPL-Caltech/MSSS

Written by Michelle Minitti, MAHLI Deputy Principal Investigator

Earth planning date: Friday, Aug. 21, 2026

After Curiosity’s 14 years on the surface, Mars continues to surprise. Both of our workspaces this week contained features unlike quite anything we have seen in the past — broad, shallow pits (like the one in the image above) dotted across the bedrock. Pits are not uncommon — when resistant nodules or pebbles weather out of their host rock, they leave behind a void. But the pits of this week were much broader and shallower than past features and were not accompanied by obvious objects that were once in the pits. MAHLI and Mastcam were particularly interested in these features, acquiring stereo mosaics of them and tightly overlapping image sets that can be turned into a digital elevation model of their structure. They were a welcome new puzzle into the processes that have affected this particular section of rocks in the stratigraphy of Mount Sharp. 

The “typical” bedrock was anything but boring. Mastcam imaged and ChemCam rastered across complex packages of layers with changes in texture and structure over short vertical differences. These might be evidence of changes in depositional conditions captured in close proximity to one another. ChemCam, MAHLI, and APXS analyzed gray, rough, resistant layers that differed from the host bedrock, likely indicative of a different chemistry. ChemCam studied one of the gray float rocks (like the small, loose pebble in the image above) that have been scattered variably across our workspaces, to try to understand the origins of these stones. Farther afield, the “Cordillera” butte continued to garner attention, with a comprehensive Mastcam mosaic covering its entire visible face, and more focused ChemCam RMI mosaics aimed at specific horizons. The “Tolhuaca” and “Potosí” buttes, which are farther south down “Valle Grande,” were also targets, with ChemCam looking for potential crossbedding and assessing the mineralogy of dark material capping Potosí. 

Our environmental science team members were just as busy, planning REMS, Mastcam, and Navcam activities at a higher-than-usual cadence to monitor a potential regional dust storm. They found by the end of the week, however, that the storm appeared to be dissipating. 

We managed to accomplish all of this despite having lost one of our planning days due to a lost downlink. 

A rover sits on the hilly, orange Martian surface beneath a flat grey sky, surrounded by chunks of rock.
NASA’s Curiosity rover at the base of Mount Sharp
NASA/JPL-Caltech/MSSS

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Sep 03, 2026

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NASA to Cover Progress 96 Spacecraft Launch, Docking

The Progress 92 cargo spacecraft from Roscosmos departs the International Space Station while soaring into an orbital sunset 267 miles above the Russia–Mongolia border.
The Roscosmos Progress 92 cargo spacecraft is photographed in March 2026 from the International Space Station as it flies into an orbital sunset 267 miles above Earth’s surface.
Credit: NASA

NASA will provide live coverage of the launch and docking of a Roscosmos cargo spacecraft carrying about three tons of food, fuel, and supplies for the crew aboard the International Space Station.

The unpiloted Progress 96 resupply spacecraft is scheduled to launch at 12:15 p.m. EDT (9:15 p.m. Baikonur time), Wednesday, Sept. 9, on a Soyuz rocket from the Baikonur Cosmodrome in Kazakhstan. NASA’s live launch coverage will begin at 12 p.m.

After a two-day trip to the space station, Progress will dock autonomously to the Poisk module’s space-facing port at 2:37 p.m., Friday, Sept. 11. NASA’s arrival coverage will begin at 1:45 p.m.

NASA will stream these events live through a variety of platforms. Learn where to watch online:

https://www.nasa.gov/live

The spacecraft will remain docked to the orbiting laboratory for about five months before departing to re-enter Earth’s atmosphere, where it will harmlessly burn up over the Pacific Ocean.

Before Progress 96 arrives, the Progress 94 spacecraft will undock from the space station at approximately 11:18 a.m., Monday, Sept. 7, for its departure and planned destructive re-entry. NASA will not stream coverage of Progress 94 undocking.

For more than 25 years, people have lived and worked continuously aboard the International Space Station, advancing scientific knowledge and making research breakthroughs not possible on Earth. The space station helps NASA understand and overcome the challenges of human spaceflight, expand commercial opportunities in low Earth orbit, and build on the foundation for long-duration missions to the Moon, as part of the Artemis program, and to Mars.

Learn more about the International Space Station, its research, and crew, at:

https://www.nasa.gov/station

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Joshua Finch / Jimi Russell
Headquarters, Washington
202-358-1100
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Sandra Jones
Johnson Space Center, Houston
281-483-5111
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Sep 03, 2026

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NASA’s IXPE Studies Magnetar

This artist’s concept depicts magnetar 1E 1547.0-5408, a rapidly rotating neutron star with magnetic fields over a trillion times stronger than Earth’s. Blue curves emanating from the star's two magnetic poles represent the magnetic field lines. The magnetar is a significant emitter of radio and X-ray radiation, with their peaks offset during its 2.1-second rotation period. This indicates the primary X-ray emitter is a secondary “hot spot” offset from the magnetic axis. These emitters are depicted as conical sections: the lighter blue radio emission peaks at the magnetic field's symmetry axis, while the darker blue X-ray emission peaks below.
NASA/Pablo Garcia

Scientists using NASA’s IXPE (Imaging X-ray Polarimetry Explorer) conducted more than 140 hours of observations of the magnetar 1E 1547-5408, shown in this Aug. 5, 2026, artist’s concept, between March and April 2025. In doing so, they may have captured empty space behaving in a way physicists have predicted for 90 years, but never directly observed.

Magnetars are a special class of neutron stars with ultra-strong magnetic fields, the strongest of any object in the observable universe, around a trillion times stronger than the strongest permanent magnets ever built on Earth.

Image credit: NASA/Pablo Garcia

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Lion Nebula Roars to Life With NASA’s Webb

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Lion Nebula Roars to Life With NASA’s Webb

JWST’s Near Infrared Camera and Mid Infrared Instrument combined image of planetary nebula NGC 2392, the Lion Nebula, against the black background of space. The nebula is at center, circular in shape, and looks like a male lion’s head. In the center is a small, pinkish-white circle with eight-point diffraction spikes, a white dwarf star. Surrounding the star are purple-pink cavernous bubbles and shell-like rings. The bubbles and shells collectively form an oval with two small, wide arcs near the top, reminiscent of a lion’s face and its ears. What appears to be extended outward from the lion’s face is a thick ring of purple-blue material. The width of the ring is consistent throughout and resembles a mane. The area closest to the lion’s face looks cloudy, while the edges of the mane look like there are clumps of dust with comet-like tails. In the background are distant galaxies and stars. Some galaxies are yellow and orange points of light and others have spiral structures. Some stars have diffraction spikes.

NASA’s James Webb Space Telescope imaged the planetary nebula NGC 2392, the Lion Nebula, using the observatory’s NIRCam and MIRI instruments. The central star’s remains are responsible for the nebula’s structure, including a lion face-shaped bubble of ionized gas and dust “mane.”

Credits:
Image: NASA, ESA, CSA, STScI; Image Processing: Alyssa Pagan (STScI)

Observing across the starry “plains” of space, NASA’s James Webb Space Telescope has taken new images of NGC 2392, nicknamed the Lion Nebula. NASA’s Hubble Space Telescope previously viewed this planetary nebula in 2000, imaging the lion face-shaped target in visible light and revealing features such as the “mane” of hazy, comet-shaped objects. Now Webb has captured a clearer, more detailed view of the Lion Nebula due to its high-resolution imaging.

Lion Nebula (NIRCam and MIRI Image)

JWSTu2019s Near Infrared Camera and Mid Infrared Instrument combined image of planetary nebula NGC 2392, the Lion Nebula, against the black background of space. The nebula is at center, circular in shape, and looks like a male lionu2019s head. In the center is a small, pinkish-white circle with eight-point diffraction spikes, a white dwarf star. Surrounding the star are purple-pink cavernous bubbles and shell-like rings. The bubbles and shells collectively form an oval with two small, wide arcs near the top, reminiscent of a lionu2019s face and its ears. What appears to be extended outward from the lionu2019s face is a thick ring of purple-blue material. The width of the ring is consistent throughout and resembles a mane. The area closest to the lionu2019s face looks cloudy, while the edges of the mane look like there are clumps of dust with comet-like tails. In the background are distant galaxies and stars. Some galaxies are yellow and orange points of light and others have spiral structures. Some stars have diffraction spikes.
NASA’s James Webb Space Telescope imaged the planetary nebula NGC 2392, the Lion Nebula, using the observatory’s NIRCam and MIRI instruments. The central star’s remains are responsible for the nebula’s structure, including a lion face-shaped bubble of ionized gas and dust “mane.”
Image: NASA, ESA, CSA, STScI; Image Processing: Alyssa Pagan (STScI)

At first glance the nebula’s overall structure in Webb’s infrared images, with both the NIRCam (Near Infrared Camera) and MIRI (Mid Infrared Instrument) instruments, may look quite similar to Hubble’s earlier visible-light view. However, Webb’s infrared vision highlights features like compact clumps of dust and a haze of ionized gas. It’s taken several thousand years for this collection of gas and dust to reach its current shape, and the nebula’s components continue to be altered.

The source of these constant changes and the reason for the Lion Nebula’s distinct appearance is located at the center: the remains of a dying star. Though it looks like the button nose of the lion, its energy and radiation are powering the intricate structures seen here.

Lion Nebula (MIRI Image)

Planetary nebula NGC 2392, also called the Lion Nebula, against the black background of space. The nebula is in the center, circular in shape, and looks like a male lion’s head. In the very center is a small, bluish-white circle with eight-point diffraction spikes, a white dwarf star. Surrounding the star are light purple-red cavernous bubbles and shell-like rings. The bubbles and shells collectively form an oval with two small, wide arcs near the top, reminiscent of a lion’s face and its ears. What appears to be extended outward from the lion’s face is a thick ring of cyan material. The width of the ring is consistent throughout and resembles a mane. The area closest to the lion’s face looks cloudy, while the edges of the mane look like there are purple clumps of dust with comet-like tails and strands. In the background are distant galaxies and stars. Some galaxies appear as small purple points of light and others with visible blue spiral structures. A couple of the stars have diffraction spikes.
NASA’s James Webb Space Telescope’s mid-infrared image of planetary nebula NGC 2392, nicknamed the Lion Nebula, highlights the varying dust structures. Some dust is being destroyed by the dying central star’s radiation, while some dust filaments manage to survive.
Image: NASA, ESA, CSA, STScI; Image Processing: Alyssa Pagan (STScI)

Massive stars undergo supernova explosions at the end of their lives, but these kinds of events are few and far in between. Most of the universe’s stars have lower masses, like the one belonging to NGC 2392. When a lower-mass star can no longer sustain itself with nuclear reactions in its core, the star becomes unstable and pulsates, losing its mass by shedding its outer layers, which then turn into shells of gas and dust called a planetary nebula. (Stars at this life stage are responsible for producing much of the universe’s observable dust.) The star’s radiation drives the ejected material away, leaving behind the very hot stellar core, also known as a white dwarf.

In the Lion Nebula’s case, the death of the oxygen-rich central star has left behind a white dwarf that is “cooking” everything from the inside and producing a bubble of ionized gas as it does. The gas bubble, which forms the lion’s face, is expanding over time and destroying dust that is in its path. Understanding why the swept-up gas has a complex structure of rings and shells, a common feature in planetary nebulae, is an ongoing endeavor.

The mane of the lion is the interior of a dust shell that is being illuminated by the white dwarf at the center. The tufts of hair, which look like cometary tails of material, are compact clumps of dust that have survived the stellar core’s radiation and protect the material that lies behind them.

Webb’s imagery “freezes” this planetary nebula in time, though the star’s death, and its tumultuous effects, go on. NGC 2392 will continue to undergo changes as its gas and dust migrate away from the stellar core. Astronomers estimate the lion will eventually disperse in approximately 10,000 years — a relatively short period in astronomical terms.

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).

To learn more about Webb, visit:

https://science.nasa.gov/webb

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The following sections contain links to download this article’s images and videos in all available resolutions followed by related information links, media contacts, and if available, research paper and Spanish translation links.

Explore more: Sonification of NGC 2392

View more: Hubble Image of NGC 2392

View more: Chandra X-ray Observatory Image of NGC 2392

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Aug 10, 2026

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Laura Betz
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
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Space Telescope Science Institute
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Space Telescope Science Institute
Baltimore, Maryland

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NASA Telescopes Create Colorful ‘Craft’ From Nearby Nebula

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NASA Telescopes Create Colorful ‘Craft’ From Nearby Nebula

This multiwavelength image of the Tarantula Nebula, one of the brightest and largest regions of star formation to Earth, shows X-rays from Chandra that reveal gas that has been blown away in winds from the surfaces of young, massive stars and heated to millions of degrees by shock waves, like sonic booms from supersonic jets. The infrared data from Webb shows thousands of young stars, plus swaths of cool dust that will provide the ingredients to one day form new stars and planets. Hubble optical data uncovers hydrogen gas that is warmer than seen with Webb, as well as some individual stars through the nebula.

Like a collage made of layered sheets of colored cellophane, a vibrant new image layers observations of a famous star-forming nebula from NASA space telescopes. The resulting cosmic “craft” reveals new details about the star formation region known as 30 Doradus, or the Tarantula Nebula.

Located in the Large Magellanic Cloud, a small neighbor galaxy to the Milky Way about 160,000 light-years from Earth, the Tarantula has thousands of young stars embedded in a vibrant honeycomb-like structure of gas and dust.

This multiwavelength image of the Tarantula Nebula, one of the brightest and largest regions of star formation to Earth, shows X-rays from Chandra that reveal gas that has been blown away in winds from the surfaces of young, massive stars and heated to millions of degrees by shock waves, like sonic booms from supersonic jets. The infrared data from Webb shows thousands of young stars, plus swaths of cool dust that will provide the ingredients to one day form new stars and planets. Hubble optical data uncovers hydrogen gas that is warmer than seen with Webb, as well as some individual stars through the nebula.
X-ray: NASA/CXC/Ohio State Univ./J. Rodriguez et al; Infrared: NASA/ESA/CSA/STScI; Optical: NASA/ESA/STScI; Image Processing: NASA/CXC/SAO/P. Edmonds

The new composite image contains X-rays from NASA’s Chandra X-ray Observatory, which has repeatedly observed the Tarantula Nebula over the course of its mission, in the layer that appears in blue. The X-ray data reveals gas blown away by winds from the surfaces of young, massive stars and heated to millions of degrees by shock waves, like sonic booms from supersonic jets.

The red represents infrared data from NASA’s James Webb Space Telescope showing thousands of young stars, plus swaths of cool dust that will provide the ingredients to form new stars and planets. Optical data in the green layer from NASA’s Hubble Space Telescope uncovers hydrogen gas that is warmer than seen with Webb, as well as some individual stars through the nebula.

The composite image shows the full Hubble and Webb images of this region, as well as a large section of the Chandra image, all recently published in a research paper in the Astrophysical Journal. In some regions the blue Chandra layer stands alone, and in others it combines with either the red Webb data or the green Hubble data. In the middle region all three images overlap to provide a holistic view in red, orange, yellow, green, and blue.

Previously, astronomers had studied the amount and the impact of energy produced by winds from young, massive stars in the Tarantula Nebula. Scientists expect that much of this energy should heat gas so that it produces X-rays. However, the research paper shows that there is much less X-ray-emitting gas in the nebula than expected. This led researchers to ask: Where has this energy gone and what tamed the Tarantula Nebula?

By studying the data from Chandra, Hubble, and Webb, combined with data from NASA’s retired Spitzer Space Telescope, the team concluded the Tarantula may be losing energy from several sources.

First, up to half of the hot gas is leaking through the shell walls of the gas and dust structures and escaping the nebula. Next, there is stirring and mixing between the cold gas near the shell walls and some of the hot gas, lowering the overall temperature of the gas. Finally, comparisons with computer simulations suggest the Tarantula may be losing energy through conduction. This involves direct physical contact between hot and cooler material, like with a frying pan on a burner, causing the hot and cooler material to equalize in temperature. In the case of the Tarantula Nebula, the hot gas would be conducting heat by being in direct contact with the cooler gas in the shells, especially in the densest regions. This scenario does not necessarily involve mixing the hot and cooler gas.

The combination of these three channels for losing large amounts of energy leads to this colorful and complex display revealed by NASA’s telescopes working together.

This multiwavelength image of the Tarantula Nebula, one of the brightest and largest regions of star formation to Earth, shows X-rays from Chandra that reveal gas that has been blown away in winds from the surfaces of young, massive stars and heated to millions of degrees by shock waves, like sonic booms from supersonic jets. The infrared data from Webb shows thousands of young stars, plus swaths of cool dust that will provide the ingredients to one day form new stars and planets. Hubble optical data uncovers hydrogen gas that is warmer than seen with Webb, as well as some individual stars through the nebula.
Tarantula Nebula / 30 Doradus, cropped version.
X-ray: NASA/CXC/Ohio State Univ./J. Rodriguez et al; Infrared: NASA/ESA/CSA/STScI; Optical: NASA/ESA/STScI; Image Processing: NASA/CXC/SAO/P. Edmonds

The paper describing these results was led by Jennifer Rodriguez of The Ohio State University in Columbus. Additional authors on the paper include Laura Lopez, Ohio State; Lachlan Lancaster, Columbia University in New York City; Anna Rosen, San Diego State University; Omnaraynai Nayak, Space Telescope Science Institute in Baltimore; Sebastian Lopez, Ohio State; Tyler Holland-Ashford, NASA’s Goddard Space Flight Center in Greenbelt, Maryland; and Trinity Webb, Ohio State.

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.

To learn more about Chandra, visit:

https://nasa.gov/chandra

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Aug 14, 2026

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Lion Nebula Roars in Webb’s Sights

JWST’s Near Infrared Camera and Mid Infrared Instrument combined image of planetary nebula NGC 2392, the Lion Nebula, against the black background of space. The nebula is at center, circular in shape, and looks like a male lion’s head. In the center is a small, pinkish-white circle with eight-point diffraction spikes, a white dwarf star. Surrounding the star are purple-pink cavernous bubbles and shell-like rings. The bubbles and shells collectively form an oval with two small, wide arcs near the top, reminiscent of a lion’s face and its ears. What appears to be extended outward from the lion’s face is a thick ring of purple-blue material. The width of the ring is consistent throughout and resembles a mane. The area closest to the lion’s face looks cloudy, while the edges of the mane look like there are clumps of dust with comet-like tails. In the background are distant galaxies and stars. Some galaxies are yellow and orange points of light and others have spiral structures. Some stars have diffraction spikes.
NASA’s James Webb Space Telescope imaged the planetary nebula NGC 2392, the Lion Nebula, using the observatory’s NIRCam and MIRI instruments. The central star’s remains are responsible for the nebula’s structure, including a lion face-shaped bubble of ionized gas and dust “mane.”
Image: NASA, ESA, CSA, STScI; Image Processing: Alyssa Pagan (STScI)

Observing across the starry “plains” of space, NASA’s James Webb Space Telescope has taken new images of NGC 2392, nicknamed the Lion Nebula. The nebula’s “mane” is clear and detailed in this image released on Aug. 10, 2026, due to Webb’s high-resolution imaging.

See more images of the Lion Nebula from Webb.

Image: NASA, ESA, CSA, STScI; Image Processing: Alyssa Pagan (STScI)

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Hubble Solves Merger Mystery From Milky Way’s Early Years

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Hubble Solves Merger Mystery From Milky Way’s Early Years

An illustration of two galaxies in the midst of a collision against a dark, star-filled background.  The collision takes up the middle third of the illustration. On the right, a larger galaxy is viewed at an angle from 11 ou2019clock to 4 ou2019clock, with a white-yellow core surrounded by mottled brown dust lanes and faint bluish spiral arms. To the left, a smaller, bright blue-white galaxy is stretched into a curved, hook-like shape as gravity distorts it. A broad, glowing bridge of pale blue gas and stars extends off the galaxy at the left, while wispy streams extend above and below the larger galaxy at the right. The words u201cArtistu2019s Conceptu201d appear in the lower left corner.
About 12 billion years ago, a dwarf galaxy known as LKH collided with a young Milky Way and merged with it. This artist’s concept portrays that collision. NASA’s Hubble Space Telescope uncovered definitive evidence of this collision by studying globular star clusters.
Illustration: NASA, ESA, Joseph Olmsted (STScI)

Our home galaxy, the Milky Way, grew to its current size in part by consuming smaller galaxies. Now, new data from NASA’s Hubble Space Telescope shows definitive evidence of a dwarf galaxy merging with the young Milky Way galaxy in the earliest phases of its evolution. This finding extends our knowledge of our galaxy’s history 1.8 billion years farther back in time than before.

The results published Monday in the journal Nature Astronomy.

The Milky Way today is a massive spiral galaxy home to hundreds of billions of stars. However, our galaxy wasn’t always so large; it has grown by forming new stars from its gas clouds as well as collecting stars, gas, and dark matter from other galaxies through mergers.

The most recent massive merger in our galaxy’s history took place with the Sagittarius dwarf galaxy, beginning over 6 billion years ago and still ongoing today. Looking back into the even more distant past, researchers learned that the Milky Way galaxy consumed another dwarf galaxy called Gaia-Sausage-Enceladus 10 billion years ago. This ancient merger greatly affected the structure of our galaxy’s disk of stars. Other, smaller mergers occurred between these two.

But our galaxy’s history doesn’t stop there. Both observations and simulations have suggested that another large merger preceded these two, though the specifics of the event have been heavily debated. Now, Hubble has uncovered definitive evidence of an earlier merger that occurred about 11.8 billion years ago, or just 2 billion years after the big bang.

“Our home is the Milky Way galaxy, but we do not know how our house was built,” said Davide Massari, lead author, Astrophysics and Space Science Observatory of Bologna in Italy. “In this paper we discover where the first significant batch of bricks came from: a dwarf galaxy that we call LKH.”

Cosmic archaeological sites

Immense astronomical surveys and precision data from spacecraft like ESA’s (European Space Agency’s) Gaia mission have been instrumental in piecing together the history of our galaxy. The farther back into our galaxy’s history that scientists attempt to look, the more difficult it becomes to tell what happened. When our galaxy was young, it was smaller and much closer in size to the galaxies it clashed with. It was also more chaotic, and it’s possible that the signs of mergers have been erased over billions of years.

It’s into this murky past that Hubble peered. Researchers used Hubble to study some of the Milky Way galaxy’s globular clusters: immense, roughly spherical collections of tens of thousands to a few million stars. Globular clusters contain some of the oldest stars in our galaxy, and they can act as cosmic archaeological sites that preserve stars from other galaxies the Milky Way galaxy has collected.

“Thanks to the high resolution and depth of Hubble imaging, we could measure the age and the metal content of these clusters with unprecedented precision,” said Chiara Zerbinati, study co-author, University of Bologna in Italy. “Coupled with measurements from Gaia, this made it possible to distinguish a population of globular clusters that are different from the others. These are the clusters that were born in LKH, and they tell us when that galaxy was devoured by ours, and how massive it was.”

The team analyzed Hubble observations of 39 globular clusters in the inner 20,000 light-years of our galaxy, where evidence of the most ancient mergers should be preserved. They expected this sample to contain globular clusters that formed within the young Milky Way galaxy as well as those collected from the Gaia-Sausage-Enceladus dwarf galaxy about 10 billion years ago.

Using Hubble’s sensitive observations to determine each cluster’s precise age and associated metallicity — the abundance of elements heavier than helium — they determined there was a third population of globular clusters in the inner regions of our galaxy. The team found that these clusters are older than the group collected in the Gaia-Sausage-Enceladus merger, but younger than those born in the Milky Way, regardless of their metal content. These  clusters, therefore, came from a separate and even earlier merger — in which the Milky Way galaxy absorbed a dwarf galaxy containing roughly 500 million times the mass of the Sun in stars, a significant fraction of our galaxy’s mass at the time. They named this dwarf galaxy Low-energy-Kraken-Heracles, or LKH, in honor of three earlier research papers that championed the idea of a merger early in our galaxy’s history.

Such a large merger so early in the Milky Way galaxy’s formation has profound implications for the evolution of our galaxy.

“Some past studies have argued that the earliest phases of our galaxy’s evolution were defined by stars born only in our galaxy,” says Massari. “Here, we have shown that stars born in external galaxies also need to be considered.”

The team plans to continue their work to unravel the history of the Milky Way galaxy by studying its globular clusters, aiming to characterize all the massive mergers that our galaxy has experienced across cosmic history.

“Hubble is observing globular clusters that have never been studied before, and this will help us characterize the merger events that are far back in time in the Milky Way galaxy’s history,” said Fernando Aguado-Agelet, co-author, University of Vigo and the University of La Laguna in Spain.

The Hubble Space Telescope has been operating for more than three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope and mission operations. Lockheed Martin Space also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.

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Last Updated

Aug 18, 2026

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Andrea Gianopoulos
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Claire Andreoli
NASA’s Goddard Space Flight Center
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Baltimore, US

Christine Pulliam
Space Telescope Science Institute
Baltimore, Maryland

Source: science.nasa.gov