In an era of large-scale surveys,
citizen science projects, and new
machine-learning techniques,
unexpected discoveries should
be expected. by Mara Johnson-Groh
Seeking the
unknown in
COSMIC
DATA
In 1964
astronomers Arno A. Penzias and Robert
W. Wilson found themselves cleaning
pigeon poop out of the Holmdel Horn Antenna, a radio telescope
in New Jersey. The data from the instrument had weird, persis-
tent noise that they couldn’t get rid of. They tried looking for
places where errant radiation signals could sneak in, and even
redesigned a part of the telescope, but the noise endured. When
nothing else seemed to work, they trapped two pigeons that had
taken up roost in the telescope and scrubbed out their droppings,
yet the noise remained. Unbeknownst to them, they were trying
to remove a fundamental signature of our universe — the cosmic
microwave background.
Just over a decade later, Wilson and Penzias won the Nobel
Prize in Physics for their serendipitous discovery of cosmic micro-
wave background (CMB) radiation. Although the pair initially had
been searching for a halo around the Milky Way, they instead
found the first light of the universe, left over from right after the
Big Bang, when photons of light were just bursting forth.
Wilson and Penzias aren’t alone in making fortuitous break-
throughs. Indeed, unexpected discoveries are almost a hallmark of
astronomy. William Herschel discovered Uranus in 1781 while
looking for binary stars, originally identifying the planet as a
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