Study Findings: Accurate Distances of the Galactic Spiral Arms from Dust-scattered X-ray Emission of Gamma-ray Bursts

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Image (Credit): An artist’s rendering of the Milky Way Galaxy illustrating the results of the recent study discussed below. The position of our Sun is also provided in the image.(ESA/Gaia/DPAC, Stefan Payne-Wardenaar, ESA/XMM-Newton and NASA/Chandra)

Astronomy & Astrophysics abstract of study findings:

The details of the spiral structure of the Milky Way are still debated due to the large uncertainties in the distance estimates obtained through the most common tracers. However, X-ray dust scattering rings produced by short extragalactic X-ray transients provide a direct method to measure the 3D distribution of interstellar clouds up to the edges of our Galaxy with a precision of a few percent. We report on an analysis of all the available XMM-Newton and Chandra follow-up observations of three low-latitude gamma-ray bursts: GRB 031203 (l ≃ 255°, b ≃ −5°), GRB 160623A (l ≃ 84°, b ≃ −3°), and GRB 221009A (l ≃ 53°, b ≃ 4°). The previous detection of X-ray rings in these observations, produced by dust clouds located beyond 5 kpc, can be associated with dust in the Perseus, Outer, and Outer Scutum-Centaurus arms, thus providing direct distance measurements to these structures along three distinct lines of sight. We identify two additional rings in the direction of GRB 160623A produced by dusty clouds at 6.91  ±  0.06 kpc and 9.9  ±  0.6 kpc, and we confirm – through a second XMM-Newton observation – the presence of one cloud at 9.7  ±  0.4 kpc toward GRB 031203. We also accurately measured the distance of dusty clouds up to 19.0  ±  0.2 kpc based on the analysis of one Chandra and four XMM-Newton observations of GRB 221009A. The small statistical and systematic uncertainties of these measurements place tight constraints on the geometry of the outer Milky Way and reveal significant deviations from current models, which critically depend on spectroscopy-based Galactic rotation curves at large distances.

Citation: Vaia, B., Fornasiero, I., Tiengo, A. et al. Accurate distances of the Galactic spiral arms from dust-scattered X-ray emission of gamma-ray bursts. A&A (2026).

DOI: https://doi.org/10.1051/0004-6361/202557431

Study-related stories:

Live Science – “’Astronomers Have To Revise Estimates’: The Milky Way May Be Larger, Heavier and More Lopsided Than We Realized”

Earth Sky – “The Milky Way’s Arms Might Not Look As We Thought”

European Space Agency – “XMM-Newton Helps Revise Distance to Outer Spiral Arms”

China Also Has a Reusable Rocket

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Image (Credit): The Long March 10b rocket’s first stage returning to a floating pad earlier today. (CCTV)

Earlier today China successfully recovered the first stage of its Long March 10b rocket (as shown above and also in a CNN video). The rocket was launched from Hainan island in southern China. 

Up to this point, only SpaceX and Blue Origin have been able to accomplish this feat. This means China is joining the U.S. in terms of reusable rockets at a time when it is also making strides in the race to the Moon.

The rocket test was also successful in putting a satellite into low-Earth orbit.

The Long March 10b rockets was built by a state-owned company and is an essential part of China’s plans to send a crew to China. It is also said to be part of China’s plans to put internet satellites into orbit, similar to SpaceX’s Starlink.

One interesting part of the recovery was the use of a large net on the platform. Chen Muye from the China Aerospace Science and Technology Corporation (the state-owned company) stated:

Net-based recovery simplifies the onboard structure, reduces weight and boosts payload capacity.

Maybe the US commercial space sector has a few things to learn from the Chinese.

Pic of the Week: Beauty and the Beast

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Image (Credit): Chinese photographers’ entry “Cosmic Neighbours: Beauty and the Beast.”(Yijing Zhu and Xinghan Yang)

This week’s image is from another finalist in the Royal Observatory Greenwich’s annual ZWO Astronomy Photographer of the Year competition. The photo is labeled “Cosmic Neighbours: Beauty and the Beast” by photographers Yijing Zhu and Xinghan Yang. It was taken in Ürümqi, Xinjiang Uyghur Autonomous Region, China.

Here is a description of the photo from the photographers:

This image captures a dramatic cosmic pairing: the serene elegance of Bode’s Galaxy (M81, left) alongside the chaotic violence of the Cigar Galaxy (M82, right). Located about 12 million light years from Earth, these two neighbours are locked in a gravitational dance that has shaped their destinies profoundly. M81 retains its perfect grand design spiral form, a picture of galactic grace.  

In stark contrast, M82 is a starburst galaxy, reeling from a close encounter with its larger companion. This gravitational disturbance has triggered a furious burst of star formation at its core, which blasts into space spectacular red filaments of superheated hydrogen gas that are clearly visible in this deep exposure.

The Smithsonian Museum’s New Exhibits

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Image (Credit): The “Discovering Our Universe” gallery at the National Air and Space Museum. (NASM)

If you are looking for something to do this summer inside an air-conditioned building, you may want to visit the Smithsonian Institute’s National Air and Space Museum in Washington, DC to enjoy some of its new exhibits.

On July 1st, a new exhibit called “Discovering Our Universe” opened to the public. It covers the tools used to understand the universe, from early land-based telescopes to the great space telescopes, such as the Hubble Space Telescope. As a result of these tools, the exhibit shares what we have already learned about what it out there as well as the plans to gather even greater amounts of data.

Other space-related exhibit openings include:

  • Living in the Space Age Hall: The display provides insight into space technologies and infrastructure that are largely invisible to the public but have a profound impact on our daily lives.
  • The Art of Air and Space: Interpretations of Flight: The display explores the relationship between art and the transformative power of the experience of flight through the display of the Museum’s permanent collection.

Of course, there is plenty more to see at the National Air and Space Museum as well as others along the National Mall. And it should be easier to get around now that the Fourth of July crowds have departed. And if you still have time, you may want to visit the Steven F. Udvar-Hazy Center in Chantilly, VA where more aircraft and spacecraft are on display.

Space Quote: The Taikonauts Are Coming!

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Image (Credit): The crew of the latest mission to China’s Tiangong space station – the Shenzhou 23 mission. (CMSA/CCTV)

“Well, I would just say, first, it’s not arguably like there- we are very much in a space race right now, and the Chinese are moving at incredible speeds, and they are certainly capable of doing what the Soviets were not during the- the first space race. The Chinese will land their taikonauts on the moon. There’s no question. The question is, will the United States return before them, and will we do so in a different way this time, when we build a base, establish that enduring presence? I think the answer is yes.“

-Statement by NASA Administrator Jared Isaacman on CBS’s Face the Nation this past Sunday. The interview addresses other issues in addition to the Artemis mission to the Moon, including efforts to save the Swift space telescope as well as the status of Blue Origin’s efforts to recover from the recent explosion of its New Glenn rocket.