Gravitational waves from inflation put a distinctive twist pattern in the polarisation of the CMB. Image aCredit: BICEP2
Astronomers announced today that they have acquired the first direct evidence that gravitational waves rippled through our infant Universe during an explosive period of growth called inflation.
This is the strongest confirmation yet of cosmic inflation theories, which say the Universe expanded by 100 trillion trillion times in less than the blink of an eye.
Our Universe burst into existence in an event known as the Big Bang 13.8 billion years ago.
Moments later, space itself ripped apart, expanding exponentially in an episode known as inflation.
Telltale signs of this early chapter in our Universe’s history are imprinted in the skies, in a relic glow called the cosmic microwave background (CMB).
But researchers had long sought more direct evidence for inflation in the form of gravitational waves, which squeeze and stretch space.
Now, with findings made at the South Pole using the BICEP2 (Background Imaging of Cosmic Extragalactic Polarization 2) telescope and submitted to the journal Nature, a team of researchers led by John Kovac at the Harvard-Smithsonian Center for Astrophysics have the first direct evidence for gravitational waves.
The data also represents the first images of these ripples in space-time.
Since the CMB is a form of light, it shows all the properties of light, including polarization.
On Earth, sunlight is scattered by the atmosphere and becomes polarized, which is why polarized sunglasses help reduce glare.
In space, the CMB was scattered by atoms and electrons and became polarized too.
“Our team hunted for a special type of polarization called ‘B-modes,’ which represents a twisting pattern in the polarized orientations of the ancient light,” Caltech’s Jamie Bock, co-leader of the Bicep Collaboration.
This B-mode signal is extremely faint.
The BICEP2 telescope at the South Pole Telescope Facility. Credit: BICEP2
In order to detect it, the team developed an array of multiple superconductor detectors, like the pixels in modern digital cameras but with the added ability to detect polarization.
When chilled, superconductors allow electrical current to flow freely with zero resistance.
The detector system in BICEP2 operates at a frosty 0.25 Kelvin, just a fraction above absolute zero.
Cosmologists are already hailing the news as a huge step.
Because it puts the previously speculative period of cosmic inflation within directly measured parameters, astronomers will now be able to discard many of the speculative theories for the origin of the Universe and concentrate on those that fit within BICEP2’s observations.