A team of astronomers has discovered that the spiral arms of the Milky Way galaxy may stretch further out into space than was previously known. The scientists made precise distance measurements of dust clouds in the arms using data from two telescopes orbiting high above Earth’s atmosphere — NASA’s Chandra, the most powerful X-ray telescope ever built, and the European Space Agency’s XMM-Newton.

Methodology and Implications

Researchers took advantage of rare, powerful gamma-ray bursts in distant galaxies. As X-rays from those bursts traveled through the Milky Way, some of the light bounced off dust clouds, creating rings that could be measured with unusual precision. This is a very direct way — relying only on geometry — to precisely measure distances to the Milky Way’s spiral arms.

The dust cloud in the most distant arm of the Milky Way was estimated to be about 3,500 light-years wide, according to the data the team collected. Astronomers have been aware of the Milky Way’s arms for at least a century, but mapping them has always been difficult since Earth is positioned inside one of them.

The recent breakthrough with studying gamma-ray bursts — a method not hampered by Earth’s position inside the galaxy — could have massive implications on how we conceptualize our home within the universe. The differences are small, but any revision of these distances is important because they are so fundamental for understanding our galaxy.

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