A strange new image of the Milky Way is promising to reveal hidden details about our galaxy and pave the way to a better understanding of how the universe was born, astronomers say.
The image, assembled with data from the Planck satellite and released on Tuesday by the European Space Agency, depicts a wraparound view of the Milky Way.
The satellite was designed to probe the most distant light in the universe not as human eye would see it, but in the microwave part of the spectrum, where signals from the most distant reaches of the universe can be detected. So, instead of the starry band familiar to backyard skywatchers everywhere, the image shows the magnetic orientation of countless microscopic dust particles that pervade the galaxy like a thin veil of smoke and give off microwaves.
To astronomers, the van Gogh-like whorls offer a telltale picture of the magnetic forces that thread through the Milky Way. To everyone else, the picture looks more like – well, a giant thumbprint.
"Your eye will do it to you," said Peter Martin, interim director of the University of Toronto' s Dunlap Institute for Astronomy and Astrophysics, and part of the team that created the image.
The Milky Way is home to some 200 billion stars, including our own sun, along with vast clouds of hydrogen gas, the raw material from which stars are made. In comparison, dust is a minor component. On average, a typical volume of space the size of a domed stadium within the galaxy contains no more than one virus-sized speck of dust. But dust can be concentrated in large quantities during the process of star formation to create solid planets like Earth.
Because of their small size, dust grains readily line themselves up with the galaxy's complicated magnetic field and so can act as a tracer that shows how the field varies in strength and orientation across the sky. This, in turn, can illuminate the role magnetism plays in the formation of new stars and planets, Prof. Martin said.
The new picture has gaps, particularly near the top and bottom, where the dust is thinner and its signal is weaker.
The horizontal line running across the middle corresponds to the mid-plane of the disc-shaped extent of the Milky Way, where the dust is most plentiful and its microwave energy is easier to detect.
A more complete view is expected in October, when Planck will weigh in on the magnetic signature of distant parts of the universe lurking behind this foreground view of the Milky Way. By carefully subtracting the Milky Way's contribution, the Planck team should have the first chance to confirm or refute a headline-making discovery reported in March of a signal from the birth of the universe, the Big Bang. If confirmed by Planck and other experiments, the Big Bang measurement has been described as one of the most important cosmic finds in over a decade.
"I think everyone is very focused [on the Planck data] thinking about what might be in there," said Duncan Hanson of McGill University, who works with the Planck mission but was not part of the team that produced the "thumbprint" image.