Saturday, September 27, 2014

Oops: "Big Bang Signal’ Could All Be Dust"

From Quanta:
There was little need, before, to know exactly how much dust peppers outer space, far from the plane of the Milky Way. Scientists understood that the dimly radiating grains aligned with our galaxy’s magnetic field and that the field’s twists and turns gave a subtle swirl to the dust glow. But those swirls were too faint to see. Only since March, when researchers claimed to have glimpsed the edge of space and time with a fantastically sensitive telescope, has the dust demanded a reckoning. For, like a cuckoo egg masquerading in a warbler’s nest, its pattern mimics a predicted signal from the Big Bang.

Now, scientists have shown that the swirl pattern touted as evidence of primordial gravitational waves — ripples in space and time dating to the universe’s explosive birth — could instead all come from magnetically aligned dust. A new analysis of data from the Planck space telescope has concluded that the tiny silicate and carbonate particles spewed into interstellar space by dying stars could account for as much as 100 percent of the signal detected by the BICEP2 telescope and announced to great fanfare this spring.

The Planck analysis is “relatively definitive in that we can’t exclude that the entirety of our signal is from dust,” said Brian Keating, an astrophysicist at the University of California, San Diego, and a member of the BICEP2 collaboration.

“We were, of course, disappointed,” said Planck team member Jonathan Aumont of the Université Paris-Sud.

The new dust analysis leaves open the possibility that part of the BICEP2 signal comes from primordial gravitational waves, which are the long-sought fingerprints of a leading Big Bang theory called “inflation.” If the universe began with this brief period of exponential expansion, as the cosmologist Alan Guth proposed in 1980, then quantum-size ripples would have stretched into huge, permanent undulations in the fabric of the universe. These gravitational waves would have stamped a swirl pattern, called “B-mode” polarization, in the cosmic microwave background, the oldest light now detectable in the sky.

But beware the cuckoo....