You're Looking at a Map of the Milky Way's Magnetic Field

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Using telescopes that study the sky in the microwave part of the electromagnetic spectrum, astronomers have successfully mapped the structure of the magnetic field of the Milky Way galaxy. While magnetic fields are difficult to measure in space, an international team of astronomers used the Teide Observatory on Tenerife in the Canary Islands to conduct 10 years of observations.

The team's collaboration, called QUIJOTE (Q-U-I JOint TEnerife) used two 2.5 m diameter telescopes, to observe the sky in the microwave part of the electromagnetic spectrum. Learning more about our galaxy's magnetic field can provide information about star formation, cosmic rays, and many other astrophysical processes.

The team said their work complements data gathered by previous space missions dedicated to the study of the cosmic microwave background radiation (CMB), the fossil radiation left behind by the Big Bang, which gave a detailed insight into the early history of the cosmos.

"These new maps give a detailed description in a new frequency range, from 10 to 40 GHz, complementing those from space missions such as Planck and WMAP," said José Alberto Rubiño, lead scientist of the QUIJOTE Collaboration, in a press release. "We have characterized the synchrotron emission from our Galaxy with unprecedented accuracy. This radiation is the result of the emission by charged particles moving at velocities close to that of light within the Galactic magnetic field. These maps, the result of almost 9,000 hours of observation, are a unique tool for studying magnetism in the universe."

The work on this mapping project started in 2012, and the team has now published a series of 6 scientific papers that provide the most accurate description to date of the polarization of the emission of the Milky Way at microwave wavelengths. Polarization is a "property of transverse waves such as light waves that specifies the direction of the oscillations of the waves and signifies the presence of a magnetic field," the team explained.

With the new maps, astronomers not only have more detailed information about the structure of the Milky Way's magnetic field, but their findings also is helping to understand the energetic processes which took place close to the birth of the Universe.

"Scientific evidence suggests that the Universe went through a phase of rapid expansion, called inflation, a fraction of a second after the Big Bang," said Rubiño. "If this is correct, we would expect to find some observable consequences when we study the polarization of the cosmic microwave background. Measuring those expected features is difficult, because they are small in amplitude, but also because they are less bright than the polarized emission from our own galaxy. However, if we finally measure them, we will have indirect information of the physical conditions in the very early stages of our Universe, when the energy scales were much higher than those that we can access or study from the ground. This has enormous implications for our understanding of fundamental physics."

The new maps from QUIJOTE have also provided new data for studying a recently detected excess of microwave emission from the center of our Galaxy. The origin of this emission is currently unknown, but it could be connected to the decay processes of dark matter particles.

Additionally, the data from the QUIJOTE collaboration allows scientists to study over 700 sources of emission in radio and microwaves, of both Galactic and extragalactic origin, meaning that the data is helping scientists to decipher signals coming from beyond our galaxy, including the cosmic microwave background radiation.

"One of the most interesting results we have found is that the polarized synchrotron emission from our Galaxy is much more variable than had been thought" said Elena de la Hoz, a researcher at the Instituto de Física de Cantabria (IFCA). "The results we have obtained are a reference to help future experiments make reliable detections of the CMB signal.

Below are links to the 6 papers published in the Monthly Notices of the Royal Astronomical Society:

Nancy Atkinson

Nancy Atkinson

Nancy Atkinson is a space journalist and author with a passion for telling the stories of people involved in space exploration and astronomy. She is currently retired from daily writing, but worked at Universe Today for 20 years as a writer and editor. She also contributed articles to The Planetary Society, Ad Astra (National Space Society), New Scientist and many other online outlets.

Her 2019 book, "Eight Years to the Moon: The History of the Apollo Missions,” shares the untold stories of engineers and scientists who worked behind the scenes to make the Apollo program so successful, despite the daunting odds against it. Her first book “Incredible Stories From Space: A Behind-the-Scenes Look at the Missions Changing Our View of the Cosmos” (2016) tells the stories of 37 scientists and engineers that work on several current NASA robotic missions to explore the solar system and beyond.

Nancy is also a NASA/JPL Solar System Ambassador, and through this program, she has the opportunity to share her passion of space and astronomy with children and adults through presentations and programs. Nancy's personal website is nancyatkinson.com