The European Space Agency’s Planck space telescope has captured an image of the Milky Way galaxy, revealing its magnetic field lines in a breakthrough that will help astronomers study the structure of the galaxy’s magnetic field and better understand the process of star formation.
The new fingerprint-like map was compiled from the first all-sky observations of polarized light emitted by interstellar dust in the Milky Way. Although the Planck mission stopped collecting data in 2013, scientists are still analyzing its huge data sets, particularly the polarized light from the early universe and from dust in the galaxy, to gather more clues to the history of the universe.
“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,” Charles Lawrence, the U.S. Planck project scientist for the mission at NASA's Jet Propulsion Laboratory, Pasadena, Calif., said in a statement.
According to scientists, light can be described as a series of waves of electric and magnetic fields that vibrate in directions that are at right angles to each other and to their direction of travel. Although these fields can vibrate at all orientations, if they happen to vibrate preferentially in certain directions, the light is “polarized.”
In space, the light emitted by stars, gas and dust can also be polarized in various ways, depending on magnetic fields. By measuring the amount of polarization in this light, astronomers can study the physical processes that caused the polarization. In particular, polarization may reveal the existence and properties of magnetic fields in the medium the light has traveled through.
The swirls, loops and arches in the new image in question trace the structure of the magnetic field in the Milky Way galaxy. Darker regions correspond to stronger polarized emission, and the striations indicate the direction of the magnetic field projected on the plane of the sky. The dark band running horizontally across the center corresponds to the galactic plane.
In addition, the image also revealed variations of the polarization direction within nearby clouds of gas and dust, which can be seen in the twisted features above and below the plane, where the magnetic field appears disorganized.