Researchers have just discovered a mysterious “humming” in the core of our galaxy: the Milky Way emits an important amount of microwave radiation, and its origin remains unknown. New cold gas clouds of carbon monoxide have also been discovered, helping astronomers locating star-forming regions.

The main objective of the Planck satellite, launched in 2009, is to study the cosmic microwave background (CMB) radiation, in order to give more detailed data than its predecessor WMAP. The CMB radiation, the first “light” ever emitted by our Universe was one of the many predictions of the famous Big Bang theory. Its study is indispensable to our understanding of the Universe, it is in a way the echo of the Universe’s birth, 13.7 billion years ago.

The Planck mission isn’t limited to the study of the CMB radiation, it is also mapping the whole sky in great details as well as our galaxy. Indeed, for the measurements to be as accurate as possible, it is necessary to remove all the radiation coming from the Milky Way, and study it very closely. That’s actually the part of Planck’s work that offered astronomers a couple of surprises.

© ESA/Planck Collaboration

During an international meeting on Monday in Bologna, Italy, Planck scientists presented the intermediate results of the mission. The final data won’t be available before 2013.

“The images reveal two exciting aspects of the galaxy in which we live,” said Planck scientist Krzysztof M. Górski from NASA’s Jet Propulsion Laboratory in Pasadena, Calif., and Warsaw University Observatory in Poland. “They show a haze around the center of the galaxy, and cold gas where we never saw it before.”

This microwave haze is being emitted from a region surrounding the core of the Milky Way; usually, this kind of emission is observed in regions with active supernovae. However, the spectrum of the detected radiation shows it is more energetic. Compared to the rest of the galaxy, the emission of the galaxy’s core is really peculiar. What could possibly generate it?

“Theories include higher numbers of supernovae, galactic winds and even the annihilation of dark-matter particles,” said Greg Dobler, Planck collaborator from the University of California in Santa Barbara, Calif.

The microwave emission seems to have the characteristics of synchrotron radiation, which is caused by particles interacting with strong magnetic fields. Dark matter, which is thought to make up more than 80% of the Universe’s mass, might also be generating this emission.

When scientists are short of explanations, dark matter often seems like a plug to make things work… Anyway, annihilation of dark matter clouds could generate enough energy to explain the phenomenon.

© ESA/Planck Collaboration

Planck hasn’t only discovered this anomaly, it has also detected several clouds of carbon monoxide, giving a new map of its distribution. Carbon monoxide clouds are used by astronomers to find other invisible clouds, made of hydrogen molecules. Molecular hydrogen is extremely difficult to detect because of its low emission rate, so carbon monoxide – which has similar processes of formation – is used to trace it. As stars form in molecular hydrogen clouds, detecting carbon monoxide indirectly allows astronomers to improve their understanding of star formation processes in the Milky Way.

That’s one of the beautiful things about astrophysics: even if on one hand something may be considered a nuisance, it is on the other hand an invaluable source of information. We will have to wait some time before Planck delivers all of its data, and we’ll have to wait even longer before any conclusions can be drawn. Who knows, maybe even bigger surprises are just waiting to be uncovered.

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