When the BICEP2 collaboration announced the discovery of gravitational waves in the cosmic microwave background radiation, it seemed that one model of how the Universe was born had been confirmed. However, although cosmic inflation is still a valid theoretical model, the BICEP2 observations have been under fire since March, causing the cosmologists to admit that their results may be skewed by intervening galactic dust.
Now it seems that BICEP2, which is headed by scientists based in the US, is looking toward its ‘competitor’ for help.
According to a BBC News report, the BICEP2 scientists are in discussions with the European Planck space telescope team to form a partnership, share data and potentially publish a joint paper later this year.
“We’re still discussing the details but the idea is to exchange data between the two teams and eventually come out with a joint paper,” Planck project scientist Jan Tauber told the BBC’s Jonathan Amos.
The question of gravitational waves embedded in the cosmic microwave background, or CMB, was thrown onto the public stage when, in March, BICEP2 scientists announced they’d acquired observational evidence of these waves from their South Pole-based telescope, providing unequivocal evidence for the inflationary period immediately after the Big Bang.
According to leading theories of the genesis of our Universe nearly 14 billion years ago, inflation had to have occurred in the fraction of a second after the Big Bang. If the theory is correct, this universal expansion would have happened faster than the speed of light, out of which the entire known Universe would have condensed. Although there is indirect evidence that this happened (the CMB itself is evidence of the ‘echo’ of the Big Bang), cosmologists have been hungrily chasing down any signal of gravitational waves etched in that background echo.
Gravitational waves are still purely theoretical, but Einstein predicted their existence when he formulated his general theory of relativity a century ago. Although they are thought to pervade the entire cosmos, and thought to have been generated in abundance after the Big Bang, gravitational waves have been notoriously difficult to detect. That was until the BICEP2 scientists announced the discovery of ‘B-mode polarization’ in the radiation emitted by the CMB.
This polarized squiggle in the CMB, according to the BICEP2 team, was evidence of gravitational waves that were generated during the inflationary period and, by extension, provided tantalizing evidence for quantum gravity around the time of the Big Bang.
But a scientific storm was quickly brewing. The BICEP2 results were announced before any research had been published to a scientific journal, and many cosmologists not associated with the work voiced their concerns.
The problem, argued critics, is that the BICEP2 telescope has to look through galactic dust within the Milky Way. This dust generates its own polarization signature that could be misconstrued as B-mode polarization from the CMB. Though the BICEP2 scientists contend that they took the necessary precautions and accounted for this dust, when their work was finally published last month, the team admitted that there was a possibility of interference.
The BICEP2 team had used incomplete Planck data to account for the dusty polarization and only when the complete Planck data set is made public later this year will cosmologists be able to sufficiently account for the interference.
Now it seems that rather than competing with their European counterparts, the BICEP2 team are going to form a partnership where data is shared and a joint paper will hopefully be published.
“Planck’s constraints on primordial B-modes will come from looking at the whole sky with relatively low sensitivity as compared to BICEP2,” said Tauber. “But because we can look at the whole sky, it makes up for some of that (lower sensitivity) at least. On the other hand, we have to deal with the foregrounds — we can’t ignore them at all.
“At the same time, we will work together with BICEP2 so that we can contribute our data to improve the overall assessment of foregrounds (dust) and the Cosmic Microwave Background. We hope to start working with them very soon, and if all goes well then we can maybe publish in the same timeframe as our main result (at the end of October).”
This would be a mutually beneficial outcome: the very detailed BICEP2 observations (that focus on a tiny part of the sky) will help confirm the general all-sky data from Planck, and the all-sky Planck data (that contains the galactic dust signal) will help the BICEP2 team confirm their historic discovery… or prove that the critics were right all along.
Source: BBC News