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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 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 5 Min Read Apocalypse When? Hubble Casts Doubt on Certainty of Galactic Collision
This NASA Hubble Space Telescope image of NGC 520 offers one example of possible encounter scenarios between our Milky Way and the Andromeda galaxy. NGC 520 is the product of a collision between two disk galaxies that started 300 million years ago. Credits:
NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and B. Whitmore (STScI) As far back as 1912, astronomers realized that the Andromeda galaxy — then thought to be only a nebula — was headed our way. A century later, astronomers using NASA’s Hubble Space Telescope were able to measure the sideways motion of Andromeda and found it was so negligible that an eventual head-on collision with the Milky Way seemed almost certain.
A smashup between our own galaxy and Andromeda would trigger a firestorm of star birth, supernovae, and maybe toss our Sun into a different orbit. Simulations had suggested it was as inevitable as, in the words of Benjamin Franklin, “death and taxes.”
But now a new study using data from Hubble and the European Space Agency’s (ESA) Gaia space telescope says “not so fast.” Researchers combining observations from the two space observatories re-examined the long-held prediction of a Milky Way – Andromeda collision, and found it is far less inevitable than astronomers had previously suspected.
“We have the most comprehensive study of this problem today that actually folds in all the observational uncertainties,” said Till Sawala, astronomer at the University of Helsinki in Finland and lead author of the study, which appears today in the journal Nature Astronomy.
His team includes researchers at Durham University, United Kingdom; the University of Toulouse, France; and the University of Western Australia. They found that there is approximately a 50-50 chance of the two galaxies colliding within the next 10 billion years. They based this conclusion on computer simulations using the latest observational data.
These galaxy images illustrate three possible encounter scenarios between our Milky Way and the neighboring Andromeda galaxy. Top left: Galaxies M81 and M82. Top right: NGC 6786, a pair of interacting galaxies. Bottom: NGC 520, two merging galaxies. Science: NASA, ESA, STScI, DSS, Till Sawala (University of Helsinki); Image Processing: Joseph DePasquale (STScI) Sawala emphasized that predicting the long-term future of galaxy interactions is highly uncertain, but the new findings challenge the previous consensus and suggest the fate of the Milky Way remains an open question.
“Even using the latest and most precise observational data available, the future of the Local Group of several dozen galaxies is uncertain. Intriguingly, we find an almost equal probability for the widely publicized merger scenario, or, conversely, an alternative one where the Milky Way and Andromeda survive unscathed,” said Sawala.
The collision of the two galaxies had seemed much more likely in 2012, when astronomers Roeland van der Marel and Tony Sohn of the Space Telescope Science Institute in Baltimore, Maryland published a detailed analysis of Hubble observations over a five-to-seven-year period, indicating a direct impact in no more than 5 billion years.
“It’s somewhat ironic that, despite the addition of more precise Hubble data taken in recent years, we are now less certain about the outcome of a potential collision. That’s because of the more complex analysis and because we consider a more complete system. But the only way to get to a new prediction about the eventual fate of the Milky Way will be with even better data,” said Sawala.
100,000 Crash-Dummy Simulations
Astronomers considered 22 different variables that could affect the potential collision between our galaxy and our neighbor, and ran 100,000 simulations called Monte Carlo simulations stretching to 10 billion years into the future.
“Because there are so many variables that each have their errors, that accumulates to rather large uncertainty about the outcome, leading to the conclusion that the chance of a direct collision is only 50% within the next 10 billion years,” said Sawala.
“The Milky Way and Andromeda alone would remain in the same plane as they orbit each other, but this doesn’t mean they need to crash. They could still go past each other,” said Sawala.
Researchers also considered the effects of the orbits of Andromeda’s large satellite galaxy, M33, and a satellite galaxy of the Milky Way called the Large Magellanic Cloud (LMC).
“The extra mass of Andromeda’s satellite galaxy M33 pulls the Milky Way a little bit more towards it. However, we also show that the LMC pulls the Milky Way off the orbital plane and away from Andromeda. It doesn’t mean that the LMC will save us from that merger, but it makes it a bit less likely,” said Sawala.
In about half of the simulations, the two main galaxies fly past each other separated by around half a million light-years or less (five times the Milky Way’s diameter). They move outward but then come back and eventually merge in the far future. The gradual decay of the orbit is caused by a process called dynamical friction between the vast dark-matter halos that surround each galaxy at the beginning.
In most of the other cases, the galaxies don’t even come close enough for dynamical friction to work effectively. In this case, the two galaxies can continue their orbital waltz for a very long time.
The new result also still leaves a small chance of around 2% for a head-on collision between the galaxies in only 4 to 5 billion years. Considering that the warming Sun makes Earth uninhabitable in roughly 1 billion years, and the Sun itself will likely burn out in 5 billion years, a collision with Andromeda is the least of our cosmic worries.
The Hubble Space Telescope has been operating for over 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, based in Denver, 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.
Explore More
Hubble Provides Bird’s-Eye View of Andromeda Galaxy’s Ecosystem (2025)
Hubble Shows Milky Way is Destined for Head-on Collision with Andromeda Galaxy (2012)
Galaxy Details and Mergers
Hubble Traces Hidden History of Andromeda Galaxy (2025)
Hubble’s High-Definition Panoramic View of the Andromeda Galaxy (2015)
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Milky Way and Andromeda Encounters
This selection of images of external galaxies illustrates three encounter scenarios between our Milky Way and the neighboring Andromeda galaxy. Top left: Galaxies M81 and M82. Top right: NGC 6786, a pair of interacting galaxies. Bottom: NGC 520, two merging galaxies.
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Last Updated Jun 02, 2025 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center
Contact Media Claire Andreoli
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
claire.andreoli@nasa.gov
Ray Villard
Space Telescope Science Institute
Baltimore, Maryland
Related Terms
Hubble Space Telescope Andromeda Galaxy Astrophysics Astrophysics Division Galaxies Goddard Space Flight Center Interacting Galaxies The Milky Way The Universe
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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 Space Force
The Department of Defense released the memorandum Interim Guidance for Executive Order 14222, “Implementing the President’s ‘Department of Government Efficiency’ Cost Efficiency Initiative.”
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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
Paul Dumbacher, right, lead test engineer for the Propulsion Test Branch at NASA’s Marshall Space Flight Center in Huntsville, Alabama, confers with Meredith Patterson, solid propulsion systems engineer, as they install the 11-inch hybrid rocket motor testbed into its cradle in Marshall’s East Test Stand. The new testbed, offering versatile, low-cost test opportunities to NASA propulsion engineers and their government, academic, and industry partners, reflects the collaboration of dozens of team members across multiple departments at Marshall. NASA/Charles Beason In June, engineers at NASA’s Marshall Space Flight Center in Huntsville, Alabama, unveiled an innovative, 11-inch hybrid rocket motor testbed.
The new hybrid testbed, which features variable flow capability and a 20-second continuous burn duration, is designed to provide a low-cost, quick-turnaround solution for conducting hot-fire tests of advanced nozzles and other rocket engine hardware, composite materials, and propellants.
Solid rocket propulsion remains a competitive, reliable technology for various compact and heavy-lift rockets as well as in-space missions, offering low propulsion element mass, high energy density, resilience in extreme environments, and reliable performance.
“It’s time consuming and costly to put a new solid rocket motor through its paces – identifying how materials perform in extreme temperatures and under severe structural and dynamic loads,” said Benjamin Davis, branch chief of the Solid Propulsion and Pyrotechnic Devices Branch of Marshall’s Engineering Directorate. “In today’s fast-paced, competitive environment, we wanted to find a way to condense that schedule. The hybrid testbed offers an exciting, low-cost solution.”
Initiated in 2020, the project stemmed from NASA’s work to develop new composite materials, additively manufactured – or 3D-printed – nozzles, and other components with proven benefits across the spacefaring spectrum, from rockets to planetary landers.
After analyzing future industry requirements, and with feedback from NASA’s aerospace partners, the Marshall team recognized that their existing 24-inch rocket motor testbed – a subscale version of the Space Launch System booster – could prove too costly for small startups. Additionally, conventional, six-inch test motors limited flexible configuration and required multiple tests to achieve all customer goals. The team realized what industry needed most was an efficient, versatile third option.
“The 11-inch hybrid motor testbed offers the instrumentation, configurability, and cost-efficiency our government, industry, and academic partners need,” said Chloe Bower, subscale solid rocket motor manufacturing lead at Marshall. “It can accomplish multiple test objectives simultaneously – including different nozzle configurations, new instrumentation or internal insulation, and various propellants or flight environments.”
“That quicker pace can reduce test time from months to weeks or days,” said Precious Mitchell, solid propulsion design lead for the project.
Engineers at NASA’s Marshall Space Flight Center in Huntsville, Alabama, assess components of the 11-inch hybrid rocket motor testbed in the wake of successful testing in June. Among Marshall personnel leading in-house development of the new testbed are, from left, Chloe Bower, subscale solid rocket motor manufacturing lead; Jacobs manufacturing engineer Shelby Westrich; and Precious Mitchell, solid propulsion design lead. NASA/Benjamin Davis Another feature of great interest is the on/off switch. “That’s one of the big advantages to a hybrid testbed,” Mitchell continued. “With a solid propulsion system, once it’s ignited, it will burn until the fuel is spent. But because there’s no oxidizer in hybrid fuel, we can simply turn it off at any point if we see anomalies or need to fine-tune a test element, yielding more accurate test results that precisely meet customer needs.”
The team expects to deliver to NASA leadership final test data later this summer. For now, Davis congratulates the Marshall propulsion designers, analysts, chemists, materials engineers, safety personnel, and test engineers who collaborated on the new testbed.
“We’re not just supporting the aerospace industry in broad terms,” he said. “We’re also giving young NASA engineers a chance to get their hands dirty in a practical test environment solving problems. This work helps educate new generations who will carry on NASA’s mission in the decades to come.”
For nearly 65 years, Marshall teams have led development of the U.S. space program’s most powerful rocket engines and spacecraft, from the Apollo-era Saturn V rocket and the space shuttle to today’s cutting-edge propulsion systems, including NASA’s newest rocket, the Space Launch System. NASA technology testbeds designed and built by Marshall engineers and their partners have shaped the reliable technologies of spaceflight and continue to enable discovery, testing, and certification of advanced rocket engine materials and manufacturing techniques.
Learn more about NASA Marshall capabilities at:
https://www.nasa.gov/marshall-space-flight-center-capabilities
Ramon J. Osorio
Marshall Space Flight Center, Huntsville, Alabama
256-544-0034
ramon.j.osorio@nasa.gov
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Last Updated Jul 12, 2024 EditorBeth RidgewayLocationMarshall Space Flight Center Related Terms
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By European Space Agency
Our galaxy has collided with many others in its lifetime. ESA’s Gaia space telescope now reveals that the most recent of these crashes took place billions of years later than we thought.
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