Planck's new all-sky views
of the Universe
DR EMILY BALDWIN
Posted: 17 February 2012
New all-sky maps from the ESA-led Planck space telescope reveal a haze of microwave emissions around the centre of our Milky Way Galaxy and previously undiscovered sites of star formation.
Planck's primary goal is to observe the relic radiation of the big bang known as the Cosmic Microwave Background (CMB), but before that can be accurately measured, all sources of foreground emission have to be removed. This includes the galactic haze and vast swaths of carbon monoxide emission revealed in the new dataset.
This all-sky image shows the distribution of the galactic haze seen by ESA's Planck at microwave frequencies (red and yellow) superimposed over the high-energy sky, as seen by NASA's Fermi Gamma-ray Space Telescope (blue). The map reveals two bubble-shaped, gamma-ray emitting structures extending from the galactic centre. Image: ESA/NASA/Planck Collaboration (microwave); NASA/DOE/Fermi LAT/D. Finkbeiner et al. (gamma rays).
“The images reveal two exciting aspects of the Galaxy in which we live,” says Planck scientist Krzysztof Gorski from NASA’s Jet Propulsion Laboratory and Warsaw University Observatory in Poland. “They show a haze around the centre of the Galaxy and cold gas where we never saw it before.”
Results from NASA's Wilkinson Microwave Anisotropy Probe (WMAP) had previously hinted at a microwave haze and the new details suggest it is a form of light energy produced when electrons accelerate through magnetic fields.
“We’re puzzled though, because this haze is brighter at shorter wavelengths than similar light emitted elsewhere in the Galaxy,” says Gorski. Proposed origins for the unusual emission include higher numbers of supernovae, galactic winds or even the annihilation of dark matter particles. Dark matter is a mysterious and invisible component of the Universe that is thought to make up roughly one quarter of all matter and has only been detected indirectly by its gravitational effects on galaxies.
“There are many possibilities and theories,” says Gregory Dobler, a postdoctoral fellow at the Kavli Institute for Theoretical Physics at UC Santa Barbara. “The problem is that the picture that has emerged challenges all of the explanations. There is no Goldilocks theory yet. None of them fit the data just right.”
Planck's all-sky image of carbon monoxide, a tracer of sites of star formation. Image: ESA/NASA/Planck Collaboration.
Planck's latest dataset also reveals the first whole-sky map of carbon monoxide, which points to cold clouds of star formation. Although predominantly made of hydrogen molecules, these frigid star-forming pods are difficult to detect because they do not readily emit radiation. Since carbon monoxide forms under similar conditions and emits more light, it can be used to highlight the clouds of hydrogen that cocoon newly forming stars.
The new 'treasure map' of molecular gas will be explored with follow-up observations to probe further the physical and chemical conditions of star formation. The maps are a crucial step towards characterizing all major foreground emissions before unveiling the CMB in intricate detail, which is expected in 2013.
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