Planck Microwave Background Radiation: Seeing the Big Bang

Two Cosmic Microwave Background anomalies hinted at by the Planck observatory's predecessor, NASA's WMAP, are confirmed in new high-precision data revealed on March 21, 2013. 

In this image, the two anomalous regions have been enhanced with red and blue shading to make them more clearly visible.

Credit: ESA and the Planck Collaboration

The universe burst into existence 13.8 billion years ago in a "Big Bang" that blew space up like a giant balloon. For nearly 400,000 years after that, the universe remained a seething-hot, opaque fog of plasma and energy.

But then, in an epoch known as recombination, the temperature dropped enough to allow the formation of electrically neutral atoms, turning the universe transparent.

Photons began to travel freely, and the light we know as the cosmic microwave background (CMB) pervaded the heavens, filled with clues about the first few moments after creation.

John Mather

"As far as we know, that's as far [back] as we can see — we get an image of the universe as it was when it was about 389,000 years old," said John Mather of NASA's Goddard Space Flight Center in Greenbelt, Md., senior project scientist for the space agency's James Webb Space Telescope, the successor to the Hubble Space Telescope.

Mather and George Smoot won the 2006 Nobel Prize in Physics for their work on NASA's Cosmic Background Explorer satellite mission.

"We believe — although it's not 100 percent proven — that spots that we see in the microwave map from when the universe was 389,000 years old were actually imposed on it when [the universe] was sub-microseconds old," Mather told reporters.

"There's an interpretive step there, but it's probably right."

The CMB, which was first detected in 1964, is strikingly uniform. But COBE discovered in 1992 that it's studded with tiny temperature fluctuations. These variations have since been mapped out more precisely by two other space missions, NASA's Wilkinson Microwave Anisotropy Probe (WMAP) and the ESA European Planck spacecraft.

The hot and cold areas — which differ from their homogeneous surroundings at a level of just 1 part per 100,000 — signify areas featuring different densities.

"You can imagine a cold spot being a gravitational overdensity; it's sitting at the bottom of a shallow gravity well," said Al Kogut of NASA Goddard, who has worked on COBE, WMAP and other efforts to map the CMB.