Astronomers discover a break in an arm of the Milky Way galaxy

While a lot about the Milky way galaxy remains unknown to us, recently astronomers have been able to discover a break in one of its arms.

Astronomers have found ‘a contingent of young stars and star-forming gas clouds’ sticking out of the Sagittarius Arm of the galaxy, according to a new study published in the Astronomy & Astrophysics journal.

The authors of the study used NASA’s Spitzer Space Telescope before its retirement in January 2020 to study the nearby portion of the Sagittarius Arm. In their observation, they found some newborn stars nestled in the gas and dust clouds (called nebulae).

The structure discovered in the Milky Way galaxy is stretching over some 3,000 light-years and looks like it is protruding out of the Sagittarius Arm of the galaxy.

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It is the first such discovery in the milky way galaxy that is seen to have a dramatically different orientation from the other arms.

“A key property of spiral arms is how tightly they wind around a galaxy,” Michael Kuhn, an astrophysicist at Caltech and lead author of the new paper, told NASA.

The circle in the middle has a pitch angle of zero degrees. Gradually as the spiral becomes more open and bigger, the pitch angle of the arms also increases.

“Most models of the Milky Way suggest that the Sagittarius Arm forms a spiral that has a pitch angle of about 12 degrees, but the structure we examined really stands out at an angle of nearly 60 degrees,” he added.

Previously, similar structures called spurs or feathers were found in the arms of other spiral galaxies. This made the scientists wonder for decades if our galaxy’s spiral arms are dotted with these arms or relatively smooth.

The data from this study could reveal that the Sagittarius Arm of our galaxy is made up of new stars which are moving in the same direction and at the same velocity.

“Distances are among the most difficult things to measure in astronomy. It is only the recent, direct distance measurements from Gaia that make the geometry of this new structure so apparent,” co-author Alberto Krone-Martins, an astrophysicist and lecturer in informatics at the University of California, Irvine and a member of the Gaia Data Processing and Analysis Consortium (DPAC), told NASA.