An uncharted region of space known as the "zone
of avoidance" lurks behind the Milky Way's center – and astronomers just
found an enormous, multi-galaxy structure there.
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A composite image showing the 58 galaxies clustered
together in the "zone of avoidance" behind the Milky Way. (Image
credit: Galdeano et al. / ESO)
Astronomers have detected an enormous extragalactic
structure hiding in an uncharted region of space far beyond the Milky Way's
center.
This phantom region, known as the zone of avoidance,
is a blank spot on our map of the universe, comprising somewhere between 10%
and 20% of the night sky. The reason we can't see it — at least with standard
visible light telescopes — is because the Milky Way's bulging center blocks our
view of it; the center of our galaxy is so dense with stars, dust and other
matter that light from the zone of avoidance gets scattered or absorbed before
reaching Earth's telescopes.
However, researchers have had better luck uncovering
the zone's secrets with telescopes that can detect infrared radiation — a type
of energy that's invisible to human eyes, but powerful enough to shine through
dense clouds of gas and dust. Infrared surveys of the zone of avoidance have
found evidence of thousands of individual galaxies shining through the cosmic
fog, though little is known about the large-scale structures that lurk there.
Now, researchers have combined data from several of
those infrared surveys to reveal the most colossal structure ever detected in
the zone of avoidance, according to a study published Oct. 28 on the preprint
database arXiv.org. (This study has not yet been peer reviewed, though it has
been submitted for review to the journal Astronomy and Astrophysics).
Located approximately 3 billion light-years from
Earth, the mysterious structure appears to be a large cluster of galaxies drawn
together by a shared center of gravity. Using observations from the VVV Survey
— a survey that studies the Milky Way's central bulge at infrared wavelengths
using the Visible and Infrared Survey Telescope for Astronomy in Chile — the
study authors found evidence of at least 58 galaxies bundled together in a
small plot of the zone of avoidance.
Galaxy clusters are the largest
gravitationally-bound objects in the universe; the largest known clusters
contain hundreds of thousands of galaxies bunched together. Unfortunately, it's
impossible to tell just how wide or massive the newly discovered cluster is,
given the vast distances and myriad obstructions sitting between the cluster's
stars and Earth.
However, the mere detection of this colossal object
shows that the zone of avoidance may not be as inscrutable as was once thought.
Future infrared studies — including potential observations by the James Webb
Space Telescope, which has already used its infrared camera to take the deepest
image of the universe to date — should further help scientists unlock the
hidden secrets beyond the Milky Way's bulge.
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