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Tuesday, 22 September 2026
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Tuesday, 22 September 2026
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ASTRONOMERS HAVE FOUND THE EDGE OF THE MILKY WAY AT LAST
Friday, 06 November 2020
Larger than our galaxy. New work has found that the Milky Way is nearly 2 million light-years long and 15 times wider than its luminous spiral disk. This number will lead to a better estimate of how big the galaxy is and how many galaxies are orbiting it.
Astronomers have long known that the brightest part of the Milky Way, the pan-shaped disk of stars containing the Sun, is 120,000 light-years across (SN: 8/1/19). There is a gas disk beyond this star disk. The vast halo of dark matter is composed of indirectly invisible particles that cover both disks and extend beyond them (SN: 10/25/16). But since the dark halo does not emit any light, its diameter is difficult to measure.
Now, Alice Deason, an astronomer at the University of Durham in the United Kingdom, and her colleagues used nearby galaxies to find the edge of the Milky Way. Give or take an accurate diameter of 1.9 million light-years, 0.4 million light-years, the group said in a study published on arXiv.org on February 21.
To put that scale forward, imagine a map where the distance between the sun and the earth is one inch. If the heart of the Milky Way is at the center of the Earth, the edge of the galaxy will be four times farther than the Moon.
Astronomers have long known that the brightest part of the Milky Way, the pan-shaped disk of stars containing the Sun, is 120,000 light-years across (SN: 8/1/19). There is a gas disk beyond this star disk. The vast halo of dark matter is composed of indirectly invisible particles that cover both disks and extend beyond them (SN: 10/25/16). But since the dark halo does not emit any light, its diameter is difficult to measure.
Now, Alice Deason, an astronomer at the University of Durham in the United Kingdom, and her colleagues used nearby galaxies to find the edge of the Milky Way. Give or take an accurate diameter of 1.9 million light-years, 0.4 million light-years, the group said in a study published on arXiv.org on February 21.
To put that scale forward, imagine a map where the distance between the sun and the earth is one inch. If the heart of the Milky Way is at the center of the Earth, the edge of the galaxy will be four times farther than the Moon.
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