Using telescopes that observe the sky in the microwave range, an international team of scientists has successfully mapped the magnetic field of our galaxy, the Milky Way.

The scientists used the QUIJOTE (QUI JOint TEnerife) Collaboration at the Teide Observatory in Tenerife in the Canary Islands. It consists of two telescopes with a diameter of 2.5 m, which observe the sky in the microwave part of the electromagnetic spectrum.

This mapping initially began in 2012. Now, nearly a decade later, scientists have provided the most accurate description to date of the polarization of the Milky Way’s emission at microwave wavelengths.

The research adds to previous space missions that looked at cosmic microwave background radiation (CMB), the fossilized radiation from the Big Bang that provided deep insight into the early history of the Universe.

In addition to mapping the magnetic structure of the Milky Way, the QUIJOTE data has been useful in other circumstances. The new data provides a new method for investigating anomalous microwave emission (AME), an emission category first identified 25 years ago. Extremely small dust grains in the interstellar medium, which are steered by the existence of the galactic magnetic field, are predicted to rotate and create AME.

The new findings helped the scientists understand the energetic processes that took place near the origin of the universe and provided information about the structure of the Milky Way’s magnetic field. The curtain of emission associated with our Milky Way must be removed before scientists can measure signals from that period. QUIJOTE’s new maps do just that, helping us better understand these elusive signals from the wider universe.

It also made it possible to study a recently detected excess of microwave emission from the center of our Milky Way galaxy. It provides some evidence that this emission could be polarized by confirming its existence.

Last but not least, QUIJOTE’s new maps have enabled the systematic study of more than 700 emission sources in radio and microwaves, both galactic and extragalactic in origin. This means the data will help scientists decipher signals from beyond our galaxy, including cosmic microwave background radiation.

José Alberto Rubiño, a chief scientist of the QUIJOTE Collaboration, said: “These new maps provide a detailed description in a new frequency range, from 10 to 40 GHz, to complement that of space missions such as Planck and WMAP. We have characterized the synchrotron emission from our Milky Way galaxy with unprecedented accuracy. This radiation is the result of the emission of charged particles moving at speeds close to that of light within the galactic magnetic field. These maps, the result of nearly 9,000 hours of observation, are a unique tool for studying magnetism in the universe.”

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

“Scientific evidence suggests that the universe went through a phase of rapid expansion called inflation a fraction of a second after the big bang. If this is correct, we expect to find some observable consequences when we study the polarization of the cosmic microwave background. Measuring these expected features is difficult because they are small in amplitude and less bright than the polarized emission from our Milky Way galaxy. However, when we finally measure them, we have indirect information about the physical conditions in the very early stages of our Universe, when energy scales were much higher than those that we can access or study from the ground. This has huge implications for our understanding of fundamental physics.”

Federica Guidi, a researcher at the Institut d’Astrophysique de Paris (IAP, Francia), said: “Quijote’s maps have also enabled the study of microwave emission from the center of our Milky Way galaxy. Recently, an excess of microwave emission has been detected from this region, the origin of which is unknown, but the origin of which may be related to the decay processes of dark matter particles. With QUIJOTE, we have confirmed the existence of this excess of radiation and found some evidence that it could be polarized.”

Magazine references:

  1. JA Rubiño-Martín, F Guidi, RT Genova-Santos, et al. QUIJOTE scientific results – IV. A survey of the northern sky in intensity and polarization at 10–20 GHz with the multi-frequency instrument. Monthly Notices of the Royal Astronomical Society, Volume 519, Issue 3, March 2023, Pages 3383-3431, DOI: 10.1093/mnras/stac3439
  2. The microwave intensity and polarization spectra of the galactic regions W49, W51 and IC443″, Tramonte et al., published in Monthly Notices of the Royal Astronomical Society. DOI: 10.1093/mnras/stac3657
  3. “The Haze as seen by QUIJOTE,” Guidi et al., published in Monthly Notices of the Royal Astronomical Society. DOI: 10.1093/mnras/stac3502
  4. “Galactic AME sources in the QUIJOTE-MFI North Hemisphere wide survey”, Poidevin et al., published in Monthly Notices of the Royal Astronomical Society. DOI: 10.1093/mnras/stac3468
  5. “Diffuse Polarized Foregrounds by Component Separation with QUIJOTE-MFI,” de la Hoz et al., published in Monthly Notices of the Royal Astronomical Society. DOI: DOI: 10.1093/mnras/stac3151
  6. “Radio Sources in the QUIJOTE-MFI Broad Survey Maps,” Herranz et al., published in Monthly Notices of the Royal Astronomical Society. DOI: 10.1093/mnras/stac3020