Milky Way's magnetic fingerprint

The European Space Agency (ESA) has released a new image from the Planck telescope, which at first glance could easily be mistaken for a frothy swirl in a coffee cup, but in fact depicts the Milky Way’s magnetic field lines, and could help astronomers understand the history of the universe.

Launched in 2009, Planck mapped the sky using two state-of-the-art instruments.

Although the mission ended last year, scientists are still analysing the data Planck collected, and hope that it will enable them to piece together how stars are formed.

To create the image, astronomers compiled information from the first all-sky observation of polarised light emitted by interstellar dust in the Milky Way, using a technique called line integral convolution.

Planck collected this data by acting like an astronomical pair of polarised sunglasses.

While the electromagnetic waves that make-up light usually vibrate in directions at right angles to each other and where they are travelling, if this is distrurbed the light becomes “polarised”. This can happen, for example, when light bounces off a reflective surface like a mirror or the sea.

The finger-print-like swirls and arcs in the new ESA image trace the structure of the magnetic field in our home galaxy.

The dark line running horizontally across the centre corresponds to the galactic plane – where the majority of the galaxy’s mass lies.

Tangles which dot the image reveal the variations of polarisation within nearby clouds of gas and dust, showing that the local magnetic field is particularly disorganized.

Surrounding the galactic plane are the darker, more turbulent-looking patches which, indicate strong polarized emissions, while the furrows show the direction of the magnetic field projected on the plane of the sky.

Scientists hope the data will enable them to investigate the early history of the cosmos, from the when the Universe was less than one second old to the period when the first stars were born, several hundred million years later.

Their findings on galactic polarization data have been published in four papers, recently submitted to the journal Astronomy & Astrophysics.

“This is the best picture we’ve ever had of the magnetic field in the Milky Way over such a large part of the sky,” said Charles Lawrence, the US Planck project scientist for the mission at Nasa’s Jet Propulsion Laboratory, California.

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