..from Top 10 Space Stories of the Year in Astronomy magazine
The universe began in a hot, cramped state about 13.8 billion years ago and has since expanded and cooled. In the early cosmos, electrons, protons, and radiation (called photons) bounced off one another constantly. About 370,000 years later, once the universe cooled to some 3000 kelvins (4940 degrees Fahrenheit), electrons and protons could combine, letting photons travel unimpeded. The distribution of matter at this “time of last scattering” left a pattern on the radiation that now fills the sky. Astronomers can study this comsic microwave background (CMB) radiation to learn about the universe as it was when light and matter separated and about all the material that radiation has traveled through since then.
The CMB is a treasure-trove that scientists have been analyzing for decades, and each new telescope tells them more details about the cosmos. The European Space Agency’s Planck satellite is the most recent space probe to map the CMB and learn about the universe’s properties. Planck launched in May 2009, and the team released its first all-sky CMB results in March 2013. Accordiing to the newest map of the CMB, the universe comprises 4.9 percent normal matter (like stars, gas, and planets), 26.8 percent dark matter (an invisible mass), and 68.3 percent dark energy (a mysterious force that seems to be speeding up the universe’s expansion).
Astronomers also used the Planck data to map the largest scales in the uiverse. “The CMB is traveling to us over billions of years, and the gravity of basically everything it goes past bends that light ever so slightly,” says Joanna Dunkley of the University of Oxford in England. Analyziing this “gravitational lensing” of the CMB gives the distribution of all the matter in the universe — normal and dark matter, from the time of last scattering to the present day.
The Planck team hopes to release its next data set in mid-2014 and incorporate another aspect of the CMB that’s much more difficult to get to — the polarization of that radiation. The CMB light waves do not vibrate in random directions. Instead, they can follow two types of patterns: E-mode or B-mode. As CMB photons collide with electrons in the universe, they scatter with a specific direction, seen as E-mode. B-mode polarization, however, is a smaller signal and thus much harder to see. One type of B-mode polarization comes from gravitational disturbances produced during a period of hyperacceleration in the universe’s first fraction of a second, called inflation.
The South Pole Telescope (SPT), which has been operating for nearly seven years from — you guessed it — the South Pole, is also looking for polarization signals. The SPT team announced July 22 that it had detected B-mode polarization within the gravitational lensing of the CMB. While this isn’t the inflation signature astronomers have been searching for, it is still an important milestone in research, as it shows that scientists are digging deeper into what the CMB holds.