Milky Way Measured From End To End, Could Help Map Galaxy

Rodiano Bonacci
Ottobre 13, 2017

Previous attempts to observe and accurately map the opposite side of the Milky Way have mainly failed because of interloping interstellar dust in the galactic plane, which blocks optical light from reaching us. Astronomers are getting better at direct measurements, though, and today (October 12, 2017) they announced they've used the Very Long Baseline Array (VLBA) to obtain a direct measurement to a star-forming region on the opposite side of our Milky Way. "In terms of tracing and understanding the spiral structure, essentially half of the Milky Way is terra incognita". If you want to understand parallax, hold one finger in front of your nose, and shut first one eye, then the other. In the case of the star-forming region called G007.47+00.05 at the other end of our galaxy, that would be "roughly equal to the angular size of a baseball on the Moon", according to a statement Thursday by the National Radio Astronomy Observatory (NRAO).

"Most of the stars and gas in our Galaxy are within this newly-measured distance from the Sun. With the VLBA, we now have the capability to measure enough distances to accurately trace the Galaxy's spiral arms and learn their true shapes", Alberto Sanna of the Max-Planck Institute for Radio Astronomy in Germany (MPIfR), said in the statement. Armed with the new ability to make direct measurements across large distances in the galaxy, astronomers going forward will be able to fill in - perhaps change - many details.

As Milky Way is a spiral galaxy with many arms (one which has our solar system), it is hard to map its structure, shape without traveling hundreds of thousands of light-years outwards to see its face.

The record-breaking measurement came with the application of a 180-year-old technique dubbed trigonometric parallax.

To do this, they used parallax measurements, which take into account differences in measurements from two points in space. The smaller the angle, the greater the distance. Over time, with advancing technologies, astronomers have been able to use parallax to directly measure greater and greater distances. This radio telescope system consists of 10 dish antennas distributed across North America, Hawaii, and the Caribbean.

"These angles that are being measured are mind-boggling", says Dame. Such regions include areas where molecules of water and methanol act as natural amplifiers of radio signals - masers, the radio-wave equivalent of lasers for light waves. However, the idea of measuring the distance to star-forming regions like this one could help with the process of mapping. We're looking all the way through the Milky Way, past its center, way out into the other side. Although we can peer along its edge while embedded in its disk, we cannot see what it looks like face-on. This task will require many more observations and much painstaking work, but, the scientists say, the tools for the job now are in hand. This technique measures the apparent shift in the sky position of a celestial object as seen from opposite sides of the Earth's orbit around the Sun.

Astronomers directly measured the distance to a region on the far side of our Milky Way Galaxy, past the Galaxy's center.

Within the next 10 years, we should have a fairly complete picture.

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