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.

NASA's HyspIRI Mission: Seeing the forest and the trees

Temperature information was collected simultaneously by the MASTER instrument. 

Red areas are composed of minerals with high silica, such as urban areas, while darker and cooler areas are composed of water and heavy vegetation. 

Credit: NASA

To Robert Green, light contains more than meets the eye: It contains fingerprints of materials that can be detected by sensors that capture the unique set of reflected wavelengths.

Scientists have used the technique, called imaging spectroscopy, to learn about water on the moon, minerals on Mars and the composition of exoplanets.

Green's favorite place to apply the technique, however, is right here on the chemically rich Earth, which is just what he and colleagues achieved this spring during NASA's Hyperspectral Infrared Imager (HyspIRI) airborne campaign.

"We have ideas about what makes up Earth's ecosystems and how they function," said Green, of NASA's Jet Propulsion Laboratory in Pasadena, Calif., and principal investigator of the campaign's Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) instrument.

"But a comprehensive understanding requires us to directly measure these things and how they change over landscapes and from season to season."

Toward that goal, scientists and engineers ultimately plan to launch the HyspIRI satellite—a mission recommended by the 2007 National Academy of Sciences Decadal Survey—to determine the spectral and thermal characteristics of the world's ecosystems, which are sensitive to changes in vegetation health, as well as detecting and understanding changes in other surface phenomena including volcanoes, wildfires and droughts.

Prior to flying the sensors in space, however, preparatory science investigations are underway using similar sensor technology installed on NASA's ER-2, a high-altitude aircraft based at NASA's Dryden Aircraft Operations Facility in Palmdale, Calif.

The first season of the HyspIRI airborne campaign concludes on April 25 after about a month of flights that spanned the state. Additional sets of California flights are planned for this summer and then this fall.

"We are collecting data over six zones across very diverse regions of California, from the coast to high-elevation terrain, from alpine areas to deserts to coastal ecosystems, and from agricultural to urban landscapes," Green said.

For example, the campaign's first test flight on March 29 collected data along a series of parallel flight lines.

The resulting image covers about six miles in width and almost 100 miles in length. One flight happened to pass over the San Andreas Fault. Inclusion of the fault in the flight plan was incidental, but it was a "spectacular" flight nonetheless, Green said.