Black Hole Eats Star: The Longest GRB Ever Seen

Unusually long gamma-ray bursts require more exotic origins than typical GRBs. This animation illustrates one proposed explanation for GRB 250702B — the merger of a stellar-mass black hole with its stellar companion. As the black hole makes its last few orbits, it pulls large amounts of gas from the star. At some point in this process, the system begins to shine brightly in X-rays. Then, as the black hole enters the main body of the star, it rapidly consumes stellar matter, blasting gamma-ray jets (magenta) outward and causing the star to explode.

Credit: NASA/LSU/Brian Monroe

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This brief animation compares the brightness and duration of a typical gamma-ray burst (yellow) to that of the July 2 outburst (magenta). A typical burst caused by the collapse of a massive star lasts less than a minute, but GRB 250702B’s activity continued for more than 7 hours, making it the longest GRB yet observed.

Credit: NASA’s Goddard Space Flight Center

Alt text: Graphs comparing typical and longest-ever GRBs

Image description: 1. A graph on a dark blue background shows white horizontal and vertical axes, respectively labeled “Time (seconds)” and “Gamma-ray Brightness,” with a spiky yellow line that peaks at about 15 seconds and continues to 60. The graph is labeled “Typical gamma-ray burst.” 2. Another graph with a spiky magenta line slides in from the right side of the frame. It compresses the previous graph, transforming it into a single vertical yellow line next to the left axis. 3. The new graph, labeled “GRB 250702B, the longest ever observed” now has a time axis labeled in hours and shows a spiky magenta line with several tall peaks, the tallest located at around 4 hours. The magenta line, representing the burst’s long-lived activity, tails off at about 8 hours.

This artist’s concept depicts GRB 250702B (left of center) erupting within its host galaxy. This powerful explosion, first detected on July 2, blasted out narrow jets of particles at nearly the speed of light and exhibited repeated outbursts that lasted over 7 hours. Astronomers conducting rapid follow-up observations with multiple telescopes around the world found that the burst occurred within a large, extremely dusty galaxy.

Credit: NOIRLab/NSF/AURA/M. Garlick

Alt text: Artist's concept of GRB erupting from a dusty galaxy

Image description: A bright, mottled cloud dominates this artistic view of a large, dusty galaxy seen nearly edge on. Layers of white, yellow, and red extend from the darker central plane, silhouetting the smoky tendrils of dust clouds in the foreground. One brilliant star dominates the scene just left of center. Long white and red rays — the burst’s particle jets — extend from the star to the top left and toward bottom center. At the fringes of the galaxy is a dark background sprinkled with faint stars.

This visualization illustrates the process of pinpointing the location of the July 2 outburst and its host galaxy. Multiple facilities in space and on Earth, collecting light across the spectrum, guided astronomers to the source.

Credit: NASA’s Goddard Space Flight Center and A. Mellinger, CMU

Image description: 1. The camera slowly pushes into a star-spangled image of the central portion of our galaxy. 2. Magenta and teal blobs cover much of the frame. Labels read “First detection” in white, “Fermi GBM” in magenta, and “Swift BAT” in teal. 3. The previous blobs fade, and new smaller blobs appear in the same color scheme. The labels read “Second detection” in white, “Fermi GBM” in magenta — the color for the larger blob — and “Swift BAT” in teal, the color of the smaller blob. 4. The blobs fade and two new irregular shapes in teal appear, the largest near the center and part of another at upper right. A nearly elliptical magenta blob also appears. Labels: “Third detection” in white, “Fermi GBM” in magenta, and “Swift BAT” in teal. 5. Text reads “Gamma-ray localization,” “Fermi GBM,” and “Swift BAT” and shows a roughly circular white patch left of center. 6. A green cross appears within the magenta shape. Text reads “Localization by” in white and “Einstein Probe” in green. 7. A dark rectangular inset expands out to the right from the green cross. It contains a black background speckled with blue-white X-ray sources, with one near center — circled as the camera pushes in — outshining the rest. Text reads “X-ray image” in white and “Swift XRT” in teal. 8. The Swift image fades into a new one filled with whitish stars. Text reads “Optical image” in white and “DSS” in cream. 9. As the camera zooms into the image, another one replaces it, this time filled with blue-white stars with orange diffraction spikes and fainter orange stars. Text reads “Optical/infrared image” in white and, in orange, “Blanco & Gemini.” 10. Zooming in, the image is replaced with a grayscale image with large fuzzy stars. At center is a faint elongated shape — the GRB’s host galaxy — which is outlined with an ellipse. Vertical and horizontal lines mark the burst’s location. Text reads “Infrared image” in white, “Gemini” in orange, and “GRB 250702B” in white within the inset. 11. The underlying image changes to one showing soft white stars with blue and red diffraction spikes. Inside the ellipse, an orange edge-on galaxy with a clear dust lane appears; the lines indicating the burst’s location are about midway between the galaxy’s left edge and center. The ellipse fades out. Text reads “Infrared image” in white, “Webb” in orange, and “GRB 250702B” in white.

On Oct. 5, NASA’s James Webb Space Telescope gave astronomers their clearest view of GRB 250702B’s edge-on host galaxy, which is nestled within a richly populated star field in the densely packed central plane of our own Milky Way galaxy. In the zoomed inset, tick marks indicate the burst’s position near the top edge of the galaxy’s dark dust lane. This location eliminates the possibility that the burst was associated with the supermassive black hole at the galaxy’s core. The full infrared image is about 2.1 arcminutes across.

Credit: NASA, ESA, CSA, H. Sears (Rutgers). Image Processing: A. Pagan (STScI)

Alt text: Webb image of GRB 250702B's star field with host galaxy inset

Image description: Against the blackness of space is a riot of white stars of varying brightness, with long diffraction spikes extending from the brightest ones. Also visible is a variety of cream-colored, orange, and brownish galaxies. A white box surrounds one galaxy in the upper left, located above a line joining the scene’s two brightest stars. Lines extend to the right from this box and lead to an enlarged inset showing the orange, edge-on disk galaxy in more detail. Horizontal and vertical lines pinpoint the burst’s location within its host galaxy. Text in the inset reads “GRB 250702B” in white.

On Oct. 5, NASA’s James Webb Space Telescope gave astronomers their clearest view of GRB 250702B’s edge-on host galaxy, which is nestled within a richly populated star field in the densely packed central plane of our own Milky Way galaxy. It is located in the upper left, between the two brightest stars in the image, and resembles an orange ellipse. The image is about 2.1 arcminutes across.

Credit: NASA, ESA, CSA, and H. Sears (Rutgers). Image Processing: A. Pagan (STScI)

Alt text: Webb infrared view of the star field around GRB 250702B's host galaxy

Image description: Against the blackness of space is a riot of white stars of varying brightness, with long diffraction spikes extending from the brightest ones. Also visible is a variety of cream-colored, orange, and brownish galaxies. The host galaxy lies at upper left, located above a line joining the scene’s two brightest stars.

The view at left shows the star field around the host galaxy of GRB 250702B. The image incorporates observations from the Gemini North telescope in Hawaii and the Dark Energy Camera mounted on the Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory in Chile. Right: A close-up view of the host galaxy taken with the Gemini North telescope. This image, which spans 9.5 arcseconds, is the result of over two hours of observations, yet the host galaxy is barely visible due to the large amount of dust surrounding it. The optical and near-infrared DECam data was acquired on July 3, while the near-infrared Gemini North data was acquired on July 20.

Credit: International Gemini Observatory/CTIO/NOIRLab/DOE/NSF/AURA; Image processing: M. Zamani & D. de Martin (NSF NOIRLab)

Alt text: Ground-based images showing the host galaxy's location

Image description: The image at left is filled with blue-white stars bearing orange diffraction spikes and fainter orange stars. A white box is superposed at center, and lines flare out from it to meet the frame of the picture at right, which is a grayscale image containing large fuzzy stars. At its center is a faint elongated shape outlined with a dashed ellipse. A short white line indicates the burst’s location within the ellipse. The text reads “Blanco & Gemini” at the bottom of the left image, “Gemini North” at the bottom of the right image, “Host Galaxy” near the ellipse, and “GRB 250702B” at the left of the line.

This image shows the star field around the host galaxy of GRB 250702B as captured by the Gemini North telescope in Hawaii and the Dark Energy Camera mounted on the Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory in Chile. The galaxy appears as a faint smudge at center. The optical and near-infrared DECam data was acquired July 3. The field of view is about 2.7 arcminutes across.

Credit: International Gemini Observatory/CTIO/NOIRLab/DOE/NSF/AURA; Image processing: M. Zamani & D. de Martin (NSF NOIRLab)

Alt text: Wide ground-based view of the host galaxy's vicinity

Image description: A wealth of blue-white stars bearing orange diffraction spikes and fainter orange stars shine against a dark background near the crowded central region of our galaxy. The burst's faint host galaxy lies at center.

This near-infrared view of GRB 250702B’s host galaxy was taken with the Gemini North telescope in Hawaii on July 20. The image spans 9.5 arcseconds and is the result of over two hours of observations, yet the host galaxy at center is barely visible due to the large amount of dust surrounding it.

Credit: International Gemini Observatory/CTIO/NOIRLab/DOE/NSF/AURA; Image processing: M. Zamani & D. de Martin (NSF NOIRLab)

Alt text: Ground-based close-up of the host galaxy's vicinity

Image description: This grayscale image shows large, fuzzy, white and gray stars, but at its center is a faint, gray elongated shape — the burst’s home galaxy.

The first precise location for GRB 250702B came early July 3 when X-Ray Telescope aboard NASA’s Neil Gehrels Swift Observatory imaged the burst (bright spot near center) in the constellation Scutum, near the crowded, dusty plane of our Milky Way galaxy. The circular field of view is 25 arcminutes across.

Credit: NASA/Swift

Alt text: X-ray image showing the location of GRB 250702B

Image description: On a black background is a circular region speckled with bluish-white X-ray sources. The brightest one, near center, is GRB 250702B.