Milky Way’s Local Arm, the region that houses our solar system, is four times bigger than previously thought


According to new research, the spiral arm of the Milky Way that houses our solar system is nearly four times larger than previously thought. The discovery indicates that the region, known as the Local Arm, takes up a greater portion of our galaxy than what scientists believed until now, measuring more than 20,000 light-years in length.

As pointed out by the researchers, however, the Local Arm is still significantly smaller than  Milky Way’s four major spiral arms: Perseus, Sagittarius, Scutum-Centaurus and Outer arms. Nevertheless, the new findings are important as they enhance our understanding of the actual shape of our galaxy. Speaking about the research, which was recently published in Science Advances journal, Mark J. Reid of the Harvard-Smithsonian Centre for Astrophysics said:

When we actually measured distances in the Local Arm we were surprised. A lot of the material that we thought was in a nearby arm was actually in the Local Arm.

For the research, an international team of scientists used the Very Long Baseline Array of telescopes, managed by the National Radio Astronomy Observatory in New Mexico. The advanced system of telescopes allowed the researchers to measure radio emissions present around the galaxy’s Local Arm, as a way of locating the denser star-forming regions in the Milky Way.

The task, as the astronomers explain, is quite challenging, since we are situated inside the spiral that is being studied. Given the great distances and the huge amounts of cosmic matter present in the Local Arm, mapping it accurately is difficult. Radio telescopes are better equipped to provide a clearer picture of the spiral arm than regular optical ones. The team went on to say:

The fundamental problem for [observing] the Milky Way is that it’s a disk-like system and we’re inside the disk. Let’s say you have a disk, and you paint a spiral pattern on the top of it. When you turn the disk sideways and look at it, you can’t see that spiral pattern… Radio telescopes can ‘see’ through the galactic plane to massive star-forming regions that trace spiral structure, while optical wavelengths will be hidden by dust.

For the sake of precision, the scientists combined the new measurements for eight, different regions surrounding the Local Arm with previous readings. The research in turn revealed that the region is nearly four times larger than previously thought. The findings also indicate that the Milky Way might be spur-shaped, instead of being a spiral.

Although around five to six times shorter in length than a few of the other spiral arms, the local region seems to boast similar size as well as rate of star formation. During the research, the team also discovered a hitherto-unknown bridge-like formation between the Local Arm and the nearby Sagittarius Arm. The findings are significant as they indicates that our galaxy is likely not shaped like a swirl. Jo Bovy from the University of Toronto said:

[Our] galaxy probably does not have one of these beautiful spiral patterns that we see in some external galaxies.

Via: National Geographic 

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