There's an anomalous cold spot in the cosmic microwave background that's baffled scientists for years. A group of astronomers now say they know what it is — a "supervoid" measuring nearly 1.8 billion light-years across.

The Cosmic Microwave Background (CMB) Cold Spot (CS) is considered the most significant anomaly observed by Planck scientists. Explanations to date have appealed to unknown or exotic physics, like the decaying of gravitational potentials caused by Dark Energy, the result of a cosmic texture (a remnant of a phase transition of the early Universe), a collision with another universe, or a wrinkle in space-time. Its discovery has even challenged the inflationary model of the Universe.


But a new theory posited by István Szapudi at the University of Hawaii in Honolulu and his colleagues suggests something far simpler: This remnant in the afterglow of the Big Bang is just a huge hole in the universe — a gap known as a cosmological void. These vast spaces, like the 250 million light-year wide Boötes void, contain virtually no matter.

The researchers came to this conclusion after analyzing an all-sky survey made by NASA's WISE satellite. Dubbed a "supervoid," it's located about 2.8 billion light-years away, stretching some 1.8 billion light-years across, making it about twice the size of the previously largest known void.


WISE and Planck maps the direction of the Cold Spot. (Credit Szapudi)

New Scientist reports:

Now the team has studied the properties of the so-called supervoid, including its alignment with the cold spot and its apparent depth. A number of techniques all yielded similar results, which the team says bolsters the case linking the void to the cold spot.

"This would be the simplest explanation requiring no exotic physics," says Szapudi. He adds that similarly simple causes may lie at the heart of other CMB mysteries, such as temperature differences that seem to be aligned along a preferred direction, dubbed the "axis of evil".


[ h/t New Scientist ]

Read the entire study at the pre-print archive arXiv: "The Cold Spot in the Cosmic Microwave Background: the Shadow of a Supervoid".


Top image: Image credit: NASA/WMAP Science Team and Rudnick et al. NRAO/AUI/NSF.

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