Jump to content

When Dead Stars Collide!


NASA

Recommended Posts

  • Publishers

4 min read

When Dead Stars Collide!

Gravity has been making waves — literally. In October 2017, the Nobel Prize in Physics was awarded for the first direct detection of gravitational waves two years earlier. Also in that month, astronomers announced a huge advance in the field of gravitational waves: For the first time, they had observed light and gravitational waves from the same source. Let’s look at what happened.

Two glowing stars with red and black surfaces sit in the middle of a starfield.
Two neutron stars are on the verge of colliding in this illustration.
NASA’s Goddard Space Flight Center

There was a pair of orbiting neutron stars in a galaxy (called NGC 4993). Neutron stars are the crushed leftover cores of massive stars (stars more than 8 times the mass of our sun) that long ago exploded as supernovae. There are many such pairs of binaries in this galaxy, and in all the galaxies we can see, but something special was about to happen to this particular pair.

Two blue spheres circle each other on a grid representing space-time. As the spheres orbit, ripples propagate outward along the grid, representing gravitational waves.
An animation of gravitational wave propagation.
R. Hurt/Caltech/JPL

Each time these neutron stars orbited, they would lose a teeny bit of gravitational energy to gravitational waves. Gravitational waves are disturbances in space-time — the very fabric of the universe — that travel at the speed of light. The waves are emitted by any mass that is changing speed or direction, like this pair of orbiting neutron stars. However, the gravitational waves are very faint unless the neutron stars are very close and orbiting around each other very fast.

Two bright spheres orbit each other, and pale arcs of blue, representing gravitational waves, ripple away from the spheres. The spheres get closer with each orbit, and as they do they distort, turning into teardrop shapes, with the points pointing toward the center. Then they touch and finally merge in a bright, white explosion.
Doomed neutron stars whirl toward their demise in this illustration. Gravitational waves (pale arcs) bleed away orbital energy, causing the stars to move closer together and merge.
NASA’s Goddard Space Flight Center/Conceptual Image Lab

The teeny energy loss caused the two neutron stars to get a teeny bit closer to each other and orbit a teeny bit faster. After hundreds of millions of years, all those teeny bits added up, and the neutron stars were very close. So close that … BOOM! … they collided. And we witnessed it on Earth on August 17, 2017.

At the center of this illustration is a bright region of light that looks like two balls that haven’t quite merged into one. Two rays of white and orange light emanate from that central collision, one up and to the right, the other down and to the left, though you can’t see the one to the left quite as well because there is also a disk of swirling material blocking the view. There is also a faint grid across the entire image, representing space-time. Ripples in the grid can be seen at the edges of the image, showing gravitational waves that had been emitted by the merger.
Illustration of two merging neutron stars. The rippling space-time grid represents gravitational waves that travel out from the collision. Narrow beams show the burst of gamma rays that are shot out just seconds after the gravitational waves. The swirling clouds of material are ejected from the merging stars.
National Science Foundation/LIGO/A. Simonnet (Sonoma State Univ.)

A couple of very cool things happened in that collision, and we expect they happen in all such neutron-star collisions. Just before the neutron stars collided, the gravitational waves were strong enough and at just the right frequency that the National Science Foundation’s Laser Interferometer Gravitational-Wave Observatory (LIGO) and European Gravitational Observatory’s Virgo could detect them. Just after the collision, those waves quickly faded out because there are no longer two things orbiting around each other!

LIGO and Virgo are ground-based detectors waiting for gravitational waves to pass through their facilities on Earth. When it is active, it can detect them from almost anywhere in space.

This animation of a gamma-ray burst shows two jets of material that look like two orange cones connected by their points and facing in opposite directions, one opening up and to the right of the center, the other opening down and to the left. The ends of the cones have bright magenta light, which represent an expanding shock wave. At the center is a wrapped-candy-shaped blue structure lined up with the jets which represents the kilonova, the neutron-rich debris of the explosion.
This illustration shows a snapshot of a gamma-ray burst caused by the merger of two neutron stars. Powerful jets (orange) emerge and plow into their surroundings, causing shock waves (pink). Just emerging at the center is the kilonova, the neutron-rich debris of the explosion (blue) powered by the decay of newly forged radioactive elements.
NASA’s Goddard Space Flight Center/Conceptual Image Lab

The other thing that happened was what we call a gamma-ray burst. When they get very close, the neutron stars break apart and create a spectacular, but short, explosion. For a couple of seconds, our Fermi satellite saw gamma rays from that explosion. Fermi’s Gamma-ray Burst Monitor is one of our eyes on the sky, looking out for such bursts of gamma rays that scientists want to catch as soon as they’re happening.

And those gamma rays came just 1.7 seconds after the gravitational wave signal. The galaxy this occurred in is 130 million light-years away, so the light and gravitational waves were traveling for 130 million years before we detected them.

This animation GIF has text “Swift Ultraviolet light,” and shows the UV light Swift detected on August 18 and 29, fading between the two. The image shows the sky, black with several small circles of light. On August 18, the central source appears as a small yellow blob with a second white ball just to the side of it. On August 29, the white ball has disappeared, leaving just the larger yellow source.
NASA’s Neil Gehrels Swift Observatory imaged the kilonova produced by merging neutron stars in the galaxy NGC 4993 (box) on Aug. 18, 2017, about 15 hours after gravitational waves and the gamma-ray burst were detected. Inset: Magnified views of the galaxy.
NASA/Swift

After that initial burst of gamma rays, the debris from the explosion continued to glow, fading as it expanded outward. Our Swift, Hubble, Chandra, and Spitzer telescopes, along with a number of ground-based observatories, were poised to look at this afterglow from the explosion in ultraviolet, optical, X-ray, and infrared light. Such coordination between satellites is something that we’ve been doing with our international partners for decades, so we catch events like this one as quickly as possible and in as many wavelengths as possible.

This animated GIF shows the region of the sky where the gravitational waves and gamma-ray burst were detected as seen by Hubble in visible light and Chandra in X-ray light, fading between the two. In visible light, there is a bright oval-shaped galaxy that takes up most of the image with a bright, white center region that fades into gray clouds around it. The site of the gamma-ray burst is outlined in a box, and shows a dim source in visible light about half way between the center of the galaxy and its edge. In X-ray light, the galaxy’s center and a couple of other sources appear as dots encircled in blue. The galaxy itself does not show up in X-rays. The site of the gamma-ray burst is a bright blue source.
The kilonova associated with GW170817 (box) was observed by NASA’s Hubble Space Telescope and Chandra X-ray Observatory. Hubble detected optical and infrared light from the hot expanding debris. Nine days later, Chandra detected the X-ray afterglow emitted by the jet directed toward Earth after it had spread into our line of sight.
NASA/CXC/E. Troja

Astronomers have thought that neutron star mergers were the cause of one type of gamma-ray burst — a short gamma-ray burst, like the one they observed on August 17. It wasn’t until we could combine the data from our satellites with the information from LIGO/Virgo that we could confirm this directly.

When this animation opens, there are concentric rings of pale blue the expand away and off the screen. At the center is a bright ball of light with two narrow cones of orange, fiery-looking material extend in opposing directions, tilted just to the right. During the first few seconds, there are magenta flashes of light that seem to be pushed along with the ends of the orange cones. The central ball expands into a puffy, electric blue cloud. The sequence represents the events that happened after two neutron stars merged, exploding in a gamma-ray burst.
This animation captures phenomena observed over the course of nine days following the neutron star merger known as GW170817, detected on Aug. 17, 2017. They include gravitational waves (pale arcs), a near-light-speed jet that produced gamma rays (magenta), expanding debris from a kilonova that produced ultraviolet (violet), optical and infrared (blue-white to red) emission, and, once the jet directed toward us expanded into our view from Earth, X-rays (blue).
NASA’s Goddard Space Flight Center/Conceptual Image Lab

That event began a new chapter in astronomy. For centuries, light was the only way we could learn about our universe. Now, we’ve opened up a whole new window into the study of neutron stars and black holes. This means we can see things we could not detect before.

This animated GIF shows a fun animation of what happened on Aug. 17, 2017. The scene shows Earth on the left side with a cartoon depiction of the Fermi satellite near the center. The image appears to ripple, starting from a dot on the upper right of the image. A speech bubble raises from two site on Earth that says, “Did you hear that?” Then, 1.7 seconds after the ripple, a magenta “blast” of light appears where the ripple originated, and the Fermi telescope has a speech bubble that says, “I sure saw it!”
On Aug. 17, gravitational waves from merging neutron stars reached Earth. Just 1.7 seconds after that, NASA’s Fermi saw a gamma-ray burst from the same event. Now that astronomers can combined what we can “see” (light) and what we can “hear” (gravitational waves) from the same event, our ability to understand these extreme cosmic phenomena is greatly enhanced.
NASA’s Goddard Space Flight Center

The first LIGO detection was of a pair of merging black holes. Mergers like that may be happening as often as once a month across the universe, but they do not produce much light because there’s little to nothing left around the black hole to emit light. In that case, gravitational waves were the only way to detect the merger.

The neutron star merger, though, has plenty of material to emit light. By combining different kinds of light with gravitational waves, we are learning how matter behaves in the most extreme environments. We are learning more about how the gravitational wave information fits with what we already know from light — and in the process we’re solving some long-standing mysteries!

Keep Exploring

Discover More Topics From NASA

View the full article

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Similar Topics

    • By NASA
      On Nov. 6, 2024, NASA Night brought cosmic excitement to the Toyota Center, where Johnson Space Center employees joined 16,208 fans who interacted with NASA as they watched the Houston Rockets claim victory over the San Antonio Spurs. 

      Energy soared as International Space Station Program Manager Dana Weigel stepped up to take the first shot. 
      International Space Station Program Manager Dana Weigel takes the first shot on Nov. 6, 2024, as the Houston Rockets go up against the San Antonio Spurs at Toyota Center.NASA/Helen Arase Vargas The ceremonial first shot also gave back to the community, with Rockets owner Tilman Fertitta donating $1,000 to the Clutch City Foundation to support underserved youth through education, sports, and disaster relief. 

      Throughout the game, Johnson employees kept the crowd engaged with NASA trivia, creating a “launch countdown” energy that had fans cheering. The arena lit up as Adam Savage narrated a video showcasing the International Space Station’s groundbreaking contributions to science. From unlocking discoveries impossible on Earth to testing critical technologies for our return to the Moon, the orbiting laboratory plays a vital role in advancing medical and social breakthroughs that enhance life on our planet.  

      The Artemis II crew also appeared on the jumbotron, reminding everyone of NASA’s mission to establish a long-term presence on the Moon for scientific discovery, economic benefits, and to inspire a new generation of explorers. 
      Dana Weigel, center, shows off a Rockets jersey on the court with Rockets mascot Clutch, left, and NASA mascot Cosmo.NASA/Helen Arase Vargas  In the Sky Court area of the stadium concourse, Johnson volunteers held “mission control” with an interactive exhibit that drew fans in like a gravitational pull. From exploring a Space Launch System model and handling a spacesuit helmet and glove to touching a 3.4-billion-year-old Moon rock collected during Apollo 17, NASA’s booth offered attendees a glimpse into space exploration. 

      Visitors had the chance to ask questions and bring home mission pins, stickers, and hands-on activities, provided by the International Space Station Program and the Artemis campaign. Seventy-five “Lucky Row” fans also received bags filled with NASA outreach materials, courtesy of the Johnson Public Engagement team. 
      NASA’s Johnson Space Center volunteers connect with fans at the game through an interactive exhibit.NASA The Orion Flight Simulator, with its realistic switches and displays, provided an immersive experience that allowed fans to dock the Orion spacecraft to humanity’s first lunar space station, Gateway.  

      More than 600 fans eagerly lined up to experience NASA’s mobile exhibit trailer in the Toyota Center parking lot—drawing lines as long as those at the box office. 
      Fans engage with the Orion Flight Simulator at NASA’s booth. NASA/Helen Arase Vargas Fans also tested their skills with a crew assembly activity focused on science, technology, engineering, and mathematics, simulating the challenges astronauts face in orbit. NASA’s inflatable mascot, Cosmo, joined the action on the court, posing for photos and adding galactic fun to events like the T-shirt giveaway. 
      The Houston Rockets mascot Clutch and NASA mascot Cosmo team up on the court at Toyota Center in Houston.NASA/Helen Arase Vargas  NASA’s presence brought together the excitement of sports with the wonder of space exploration, inspiring fans to keep shooting for the stars. 

      View more images from the event below.  
      View the full article
    • By NASA
      The NASA Ames Science Directorate recognizes the outstanding contributions of (pictured left to right) America Reyes Wang, Sepideh Khajehei, Julie Nottage, and Ryan Felton. Their commitment to the NASA mission represents the talent, camaraderie, and vision needed to explore this world and beyond.
      Space Biosciences Star: America Reyes Wang
      America Reyes Wang serves as the Space Biology Biospecimen Sharing Program (BSP) Lead in the Space Biosciences Research Branch, where she guides a team of support scientists and a logistics coordinator in planning and performing detailed, collaborative dissections to maximize the scientific return from biological investigations. Under her leadership, the BSP team has contributed over 5,000 samples to the NASA Biological Institutional Scientific Collection (NBISC), approximately half of which were collected in the last 10 months.
      Earth Science Star: Sepideh Khajehei
      Sepideh Khajehei is a NASA Earth eXchange (NEX) Data and Research Scientist in the Biospheric Science Branch, for the Bay Area Environmental Research Institute. She is recognized for her dedicated support of the NASA Administrator’s Earth Information Center, and recently for her outstanding support for an urgent request to revise climate indices just days before the October 7, 2024, opening of NASA’s Hometown Climate Dashboard at the Smithsonian Institute in Washington, D.C.
      Space Science & Astrobiology Star: Julie Nottage
      Julie Nottage continuously goes above and beyond in her role as the Space and Earth Sciences Facilities Service Manager.  She keeps a multi-use interdisciplinary science building running across all aspects of operations and is the go-to person for any problem.  Her can-do approach and wealth of knowledge ensures the facility’s high-quality operation that enables scientists and engineers to focus on their research and instrument work.  Her quality work and extensive coordination of the Voluntary Protection Program allowed these month-long inspections to run smoothly with an improved safety outcome.
      Space Science & Astrobiology Star: Ryan Felton
      Ryan Felton, a NASA Postdoctoral Management Fellow with the Exobiology Branch, is recognized for his successful coordination of an engaging community-wide seminar series focused on Artificial Intelligence/Machine Learning (AI/ML). This seminar series featured four speakers so far over six months on a variety of exciting topics to advance AI/ML knowledge and use in the branch’s research.
      View the full article
    • By NASA
      A preview image of the Minecraft world inspired by NASA’s James Webb Space Telescope. Credit: Minecraft NASA invites gamers, educators, and students to grab their pickaxe and check out its latest collaboration with Minecraft exploring a new world inspired by the agency’s James Webb Space Telescope. The partnership allows creators to experience NASA’s discoveries with interactive modules on star formation, planets, and galaxy types, modeled using real Webb images.
      The James Webb Space Telescope Challenges were developed to inspire the next generation of scientists, engineers, and technicians. Through the game, students can immerse themselves in the science and technology behind Webb, deepening their understanding of NASA’s mission and sparking an interest in the real-world applications of science, technology, engineering, and math (STEM).
      “We’re thrilled to bring the wonders and science of NASA’s James Webb Space Telescope into the hands of the Artemis Generation through this exciting Minecraft collaboration,” said NASA Deputy Administrator Pam Melroy. “This collaboration is yet another way anyone can join NASA as we explore the secrets of the universe and solve the world’s most complex problems, making space exploration engaging for learners of all ages.” 
      NASA’s James Webb Space Telescope launched to space Dec. 25, 2021, and has gone on to make detailed observations of the planets within our own solar system, peer into the atmospheres of planets orbiting other stars outside our solar system, and capture images and spectra of the most distant galaxies ever detected.
      “NASA’s collaboration with Minecraft allows players to experience the excitement of one of the most ambitious space missions ever,” said Mike Davis, Webb project manager at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “No matter where Webb looks, it sees something intriguing, setting the stage for amazing discoveries yet to come. As people explore the Minecraft world of Webb, we hope they will be inspired to carry that interest further and maybe someday help NASA build future space telescopes.”
      Webb is the world’s premier space science observatory. The space telescope 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).
      NASA’s Office of STEM Engagement provides unique opportunities for students to learn about STEM. In 2023, NASA partnered with Minecraft on an Artemis Challenge where users could build and launch a rocket, guide their Orion spacecraft, and even establish a lunar base alongside their team. Through collaboration with partners such as Microsoft, NASA can share the excitement of space exploration with even more students who are part of the Artemis Generation.
      Learn more about how NASA’s Office of STEM Engagement is inspiring the next generation of explorers at:
      https://www.nasa.gov/stem
      View the full article
    • By European Space Agency
      Looking deep into the early Universe with the NASA/ESA/CSA James Webb Space Telescope, astronomers have found something unprecedented: a galaxy with an odd light signature, which they attribute to its gas outshining its stars.
      View the full article
    • By NASA
      4 Min Read In Odd Galaxy, NASA’s Webb Finds Potential Missing Link to First Stars
      What appears as a faint dot in this James Webb Space Telescope image may actually be a groundbreaking discovery. Full image and details below. Credits:
      NASA, ESA, CSA, STScI, Alex Cameron (Oxford) Looking deep into the early universe with NASA’s James Webb Space Telescope, astronomers have found something unprecedented: a galaxy with an odd light signature, which they attribute to its gas outshining its stars. Found approximately one billion years after the big bang, galaxy GS-NDG-9422 (9422) may be a missing-link phase of galactic evolution between the universe’s first stars and familiar, well-established galaxies.
      Image A: Galaxy GS-NDG-9422 (NIRCam Image)
      What appears as a faint dot in this James Webb Space Telescope image may actually be a groundbreaking discovery. Detailed information on galaxy GS-NDG-9422, captured by Webb’s NIRSpec (Near-Infrared Spectrograph) instrument, indicates that the light we see in this image is coming from the galaxy’s hot gas, rather than its stars. Astronomers think that the galaxy’s stars are so extremely hot (more than 140,000 degrees Fahrenheit, or 80,000 degrees Celsius) that they are heating up the nebular gas, allowing it to shine even brighter than the stars themselves. NASA, ESA, CSA, STScI, Alex Cameron (Oxford) “My first thought in looking at the galaxy’s spectrum was, ‘that’s weird,’ which is exactly what the Webb telescope was designed to reveal: totally new phenomena in the early universe that will help us understand how the cosmic story began,” said lead researcher Alex Cameron of the University of Oxford.
      Cameron reached out to colleague Harley Katz, a theorist, to discuss the strange data. Working together, their team found that computer models of cosmic gas clouds heated by very hot, massive stars, to an extent that the gas shone brighter than the stars, was nearly a perfect match to Webb’s observations.
      “It looks like these stars must be much hotter and more massive than what we see in the local universe, which makes sense because the early universe was a very different environment,” said Katz, of Oxford and the University of Chicago.
      In the local universe, typical hot, massive stars have a temperature ranging between 70,000 to 90,000 degrees Fahrenheit (40,000 to 50,000 degrees Celsius). According to the team, galaxy 9422 has stars hotter than 140,000 degrees Fahrenheit (80,000 degrees Celsius).
      The research team suspects that the galaxy is in the midst of a brief phase of intense star formation inside a cloud of dense gas that is producing a large number of massive, hot stars. The gas cloud is being hit with so many photons of light from the stars that it is shining extremely brightly.
      Image B: Galaxy GS-NDG-9422 Spectrum (NIRSpec)
      This comparison of the data collected by the James Webb Space Telescope with a computer model prediction highlights the same sloping feature that first caught the eye of astronomer Alex Cameron, lead researcher of a new study published in Monthly Notices of the Royal Astronomical Society. The bottom graphic compares what astronomers would expect to see in a “typical” galaxy, with its light coming predominantly from stars (white line), with a theoretical model of light coming from hot nebular gas, outshining stars (yellow line). The model comes from Cameron’s collaborator, theoretical astronomer Harley Katz, and together they realized the similarities between the model and Cameron’s Webb observations of galaxy GS-NDG-9422 (top). The unusual downturn of the galaxy’s spectrum, leading to an exaggerated spike in neutral hydrogen, is nearly a perfect match to Katz’s model of a spectrum dominated by super-heated gas.
      While this is still only one example, Cameron, Katz, and their fellow researchers think the conclusion that galaxy GS-NDG-9422 is dominated by nebular light, rather than starlight, is their strongest jumping-off point for future investigation. They are looking for more galaxies around the same one-billion-year mark in the universe’s history, hoping to find more examples of a new type of galaxy, a missing link in the history of galactic evolution.
      NASA, ESA, CSA, Leah Hustak (STScI) In addition to its novelty, nebular gas outshining stars is intriguing because it is something predicted in the environments of the universe’s first generation of stars, which astronomers classify as Population III stars.
      “We know that this galaxy does not have Population III stars, because the Webb data shows too much chemical complexity. However, its stars are different than what we are familiar with – the exotic stars in this galaxy could be a guide for understanding how galaxies transitioned from primordial stars to the types of galaxies we already know,” said Katz.
      At this point, galaxy 9422 is one example of this phase of galaxy development, so there are still many questions to be answered. Are these conditions common in galaxies at this time period, or a rare occurrence? What more can they tell us about even earlier phases of galaxy evolution? Cameron, Katz, and their research colleagues are actively identifying more galaxies to add to this population to better understand what was happening in the universe within the first billion years after the big bang.
      “It’s a very exciting time, to be able to use the Webb telescope to explore this time in the universe that was once inaccessible,” Cameron said. “We are just at the beginning of new discoveries and understanding.”
      The research paper is published in Monthly Notices of the Royal Astronomical Society.
      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).
      Downloads
      Right click any image to save it or open a larger version in a new tab/window via the browser’s popup menu.
      View/Download all image products at all resolutions for this article from the Space Telescope Science Institute.
      View/Download the research results from the Monthly Notices of the Royal Astronomical Society.
      Media Contacts
      Laura Betz – laura.e.betz@nasa.gov, Rob Gutro – rob.gutro@nasa.gov
      NASA’s Goddard Space Flight Center, Greenbelt, Md.
      Christine Pulliam – cpulliam@stsci.edu, Leah Ramsay – lramsay@stsci.edu
      Space Telescope Science Institute, Baltimore, Md.
      Related Information
      Read more: “What Were the First Stars Like?”
      Watch: “Massive Stars: Engines of Creation”
      Learn about spectroscopy: “Spectroscopy 101 – Introduction”
      Star Lifecycle
      More Webb News
      More Webb Images
      Webb Science Themes
      Webb Mission Page
      Related For Kids
      What is a galaxy?
      What is the Webb Telescope?
      SpacePlace for Kids
      En Español
      Ciencia de la NASA
      NASA en español 
      Space Place para niños
      Keep Exploring Related Topics
      James Webb Space Telescope


      Webb is the premier observatory of the next decade, serving thousands of astronomers worldwide. It studies every phase in the…


      Stars



      Stars Stories



      Galaxies


      Share








      Details
      Last Updated Sep 24, 2024 Editor Marty McCoy Contact Laura Betz laura.e.betz@nasa.gov Related Terms
      Astrophysics Galaxies Goddard Space Flight Center James Webb Space Telescope (JWST) Science & Research Stars The Universe View the full article
  • Check out these Videos

×
×
  • Create New...