This image portrays the Large and Small Magellanic Clouds – two spectacular, naked-eye companion galaxies to our own Milky Way Galaxy; and a filament of dust and gas approximately 300 light-years away. The image is based on data from ESA’s Planck satellite, which scanned the sky between 2009 and 2013 to study the cosmic microwave background (CMB). While doing so, Planck also detected foreground emission from material in the Milky Way, as well as from other galaxies.
The Large and Small Magellanic Clouds and an interstellar filament. Image credit: ESA / Planck Collaboration.
The Large Magellanic Cloud, around 160,000 light-years away, is the large red and orange blob close to the center of the image. The Small Magellanic Cloud, around 200,000 light-years away, is the triangular-shaped object to the lower left.
Planck detected the dust between the stars pervading the Magellanic Clouds while surveying the sky to study the CMB – the most ancient light in the Universe’s history.
In fact, Planck detected emission from virtually anything that shone between itself and the cosmic background at its sensitive frequencies. These foreground contributions include many galaxies, near and far, as well as interstellar material in the Milky Way Galaxy.
Astronomers need to remove them in order to access the wealth of cosmic information contained in the ancient light. But, as a bonus, they can use the foreground observations to learn more about how stars form in galaxies, including our own.
Interstellar dust from the diffuse medium that permeates our Galaxy can be seen as the mixture of red, orange and yellow clouds in the upper part of this image, which belong to a large star-forming complex in the southern constellation Chameleon.
In addition, a filament can also be seen stretching from the dense clouds of Chameleon, in the upper left, towards the opposite corner of the image.
Apparently located between the two Magellanic Clouds as viewed from Planck, this dusty filament is in fact much closer to us, only about 300 light-years away.
The image shows how well this structure is aligned with the galaxy’s magnetic field, which is represented as the texture of the image and was estimated from Planck’s measurements.
By comparing the structure of the magnetic field and the distribution of interstellar dust in the Milky Way, scientists can study the relative distribution of interstellar clouds and the ambient magnetic field.
While in the case of the filamentary cloud portrayed in this image, the structure is aligned with the direction of the magnetic field, in the denser clouds where stars form filaments tend to be perpendicular to the interstellar magnetic field.
