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A Tour of NASA's Chandra Examines Milky Way at Arms' Length - More Videos
A Tour of NASA's Chandra Examines Milky Way at Arms' Length - More Videos
- The outer spiral arms of the Milky Way galaxy may be farther away than scientists previously thought.
- This discovery was made by measuring light echoes from distant gamma-ray bursts using NASA’s Chandra and ESA’s XMM-Newton.
- Even a small change in the distance to these arms has a significant impact on our understanding of the Milky Way’s structure.
- While this technique is powerful, gamma-ray bursts are rare so it may be difficult to use them to measure distances to other spiral arms.
The graphic illustrates a new result that indicates the outer spiral arms in the Milky Way galaxy may reach wider than previously thought, according to data from NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton. This finding could lead astronomers to adjust their understanding of our home galaxy’s structure and is described in our latest press release.
The sequence begins with an artist’s concept showing the Milky Way galaxy as seen from above with the estimated positions of spiral arms based on previously-obtained data from various telescopes. The second artist’s concept shows new positions of the two spiral arms most distant from the center of the galaxy, that have been adjusted based on X-ray data from Chandra and XMM-Newton.
The sequence begins with an artist’s concept showing the Milky Way galaxy as seen from above with the estimated positions of spiral arms based on previously-obtained data from various telescopes. The second artist’s concept shows new positions of the two spiral arms most distant from the center of the galaxy, that have been adjusted based on X-ray data from Chandra and XMM-Newton.
An artist’s concept showing the Milky Way galaxy as seen from above, with the estimated positions of spiral arms based on previous data, in blue. Overlaid on this is an updated view of the Milky Way showing different positions for the two outermost spiral arms, shown in red and bordered by dashed lines. Both arms may be more distant than previously thought, based on newly processed X-ray data from Chandra and XMM. Credit: NASA/CXC/SAO/M.Weiss
A team of researchers determined the distances to these spiral arms by studying rings around gamma-ray bursts (GRBs), some of the brightest bursts of light in the universe. GRBs happen when massive stars collapse or neutron stars merge, and they are located at enormous distances — well beyond the confines of our galaxy. The distance measurement technique capitalized on the phenomenon of light echoes, where the light from the GRB bounced off intervening dust clouds in the spiral arms. The diameters of the rings in X-rays give the distances to Earth, with larger rings being generated by dust clouds closer to us.
A composite image shows one set of light echoes used in the new study to determine the distance to the Milky Way’s spiral arms. This image combines X-ray data from Chandra (blue) and optical data from Pan-STARRS (red, green and blue) showing X-ray rings generated by the GRB. The GRB is located at the center of the circles defining the rings, to the left of the X-ray data outlined by the white square.
A team of researchers determined the distances to these spiral arms by studying rings around gamma-ray bursts (GRBs), some of the brightest bursts of light in the universe. GRBs happen when massive stars collapse or neutron stars merge, and they are located at enormous distances — well beyond the confines of our galaxy. The distance measurement technique capitalized on the phenomenon of light echoes, where the light from the GRB bounced off intervening dust clouds in the spiral arms. The diameters of the rings in X-rays give the distances to Earth, with larger rings being generated by dust clouds closer to us.
A composite image shows one set of light echoes used in the new study to determine the distance to the Milky Way’s spiral arms. This image combines X-ray data from Chandra (blue) and optical data from Pan-STARRS (red, green and blue) showing X-ray rings generated by the GRB. The GRB is located at the center of the circles defining the rings, to the left of the X-ray data outlined by the white square.
The researchers used three different GRBs to determine the distances to three spiral arms in the Milky Way. In order of increasing distances from the Galactic Center, they are the Perseus, the Outer, and the Outer Scutum-Centaurus arms. Along the direction to one of the GRBs they found that both the Outer and Outer Scutum-Centaurus arms are about 10% more distant than astronomers previously thought. The differences in the positions of these spiral arms based on the new study are depicted in another artist’s illustration where the updated positions of outermost spiral arms are shown in red and bordered by dashed lines.
Although this technique is a major improvement, it may be difficult to use it for further measurements because bright GRBs that are visible through the plane of the galaxy are rare.
A paper describing these results, led by Beatrice Vaia of Scuola Universitaria Superiore IUSS Pavia and University of Trento in Italy, has been recently published by the Astronomy & Astrophysics journal and is available here. NASA's Marshall Space Flight Center 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.
Source: NASA’s Chandra X-ray Observatory
Fast Facts for Milky Way Spiral Arms:
Credit: X-ray: NASA/CXC/INAF/B. Vaia et al.; Optical: Pan-STARRS; Image processing: NASA/CXC/SAO/N.Wolk & P.Edmonds; Illustration: NASA/CXC/SAO/M.Weiss
Release Date: July 1, 2026Scale: Image is about 22 arcmin (400 light-years) across.
Category: Milky Way Galaxy
Coordinates (J2000): RA 19h 12m 24s | Dec +19° 43´ 46"
Constellation: Sagitta
Observation Dates: October 22, 2022
Observation Time: 6 hours 2
Obs. ID: 27517
Instrument: ACIS
References: B. Vaia et al. 2026, A&A, in press
Color Code: X-ray: blue; Optical: red, green, and blue
Distance Estimate: About 62,000 light-years from Earth
