Starry night: brushstrokes of dust in the Milky Way

Image of the Milky way

(Credit: ESA/Planck Collaboration. Acknowledgment: M.-A. Miville-Deschênes, CNRS – Institut d'Astrophysique Spatiale, Université Paris-XI, Orsay, France)

The flowing textures and vivid colours in this striking image call to mind Van Gogh's most famous painting. In spite of its impressionistic beauty, though, this is not an artist's illustration—it is actually a snapshot of shimmering dust in a small patch of the southern sky captured by the Planck Space Telescope.

The colours in the image map how dust in our galaxy, the Milky Way, scatters light. Planck measured the direction of light emitted by the dust, with blue indicating less intensity and red showing the highest levels of dust concentration. The warm colours in the upper part of the image show where dust is most dense along the plane of our galaxy (imagine looking at the Milky Way side-on, like the edge of a pancake), where most of its mass lies. The folds and textures in the image show the polarised light, revealing the alignment of dust grains in the Milky Way's magnetic field.

Astronomers, including scientists at the University of British Columbia and the University of Toronto, are particularly interested in the dotted region of the image, which generated considerable excitement in 2013 when a ground-based experiment at the South Pole, BICEP2, surveyed the same patch of sky and yielded a possible detection of what are known as primordial gravitational waves: ripples in space-time which can be distinguished as a swirly pattern in the polarization of the Cosmic Microwave Background (CMB), the most ancient light in the history of the Universe. However, a joint analysis of data from BICEP2, the Keck Array, and Planck has revealed that the early evidence of gravitational waves was a false alarm, likely caused by dust in our Galaxy, as seen in this image.

The Canadian Space Agency (CSA) provides funding for two Canadian teams at the University of British Columbia and the University of Toronto, who are part of the Planck satellite mission. Read more about Canada's involvement in Planck: www.asc-csa.gc.ca/eng/satellites/planck/.