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FRBs and variable forces: a big week for astronomy

Parkes turns up mystery objects, UNSW tests Einstein

Astronomers trawling through the archives of the Parkes Radio Telescope have turned up a new and mystifying class of intergalactic radio transmissions: FRBs, or fast radio bursts.

Similar but not identical to the well-known gamma ray bursts, FRBs appear as flashes that descend through a bunch of wavelengths (from shorter to longer) because of their ten-billion-year trip and the probably relativistic events that gave rise to them.

Reconstructed to their original wave-shape, they emerge to have been of millisecond duration emitted more than ten billion years ago – and their origins are as yet unknown. However, as one of the team that analysed the signals, Matthew Bailes, pro vice-chancellor of research at Swinburne University notes at The Conversation, the bursts confirm a previous but controversial event.

That event, the extra-galactic “Lorimer Burst”, was also observed in Parkes Telescope archival data, emanated from the direction of the Large Magellanic Clouds, was so singular and inexplicable that at the time, it was conjectured that it could have been a bug in the equipment.

As the international group of astronomers that worked on the FRBs notes in the abstract of their paper in Science: “Most galaxy and intergalactic medium models suggest that they have cosmological redshifts of 0.5 to 1 and distances of up to 3 gigaparsecs. No temporally coincident x- or gamma-ray signature was identified in association with the bursts”.

They add that with further analysis, the FRBs could help “determine the baryonic content of the Universe” or, as Bailes more simply puts it, they would help count the number of electrons in the Universe.

Their work began in 2012, when University of Manchester PhD student Dan Thornton began looking at “off-plane” (that is, away from the plane of our own galaxy) regions that are commonly considered boring. Since then, four FRBs have been discovered.

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White Dwarfs and the laws of physics

The other biggie from astronomy is an announcement from the University of New South Wales, which believes new work with a white dwarf star might provide evidence that different regions of the universe have subtly different laws of physics.

Their work, published in Physical Review Letters, suggests the tantalising and controversial possibility that the electromagnetic force is not uniform everywhere.

“Dr Julian Berengut and his colleagues used the Hubble Space Telescope to measure the strength of the electromagnetic force – known as alpha – on a white dwarf star,” UNSW said in a media release.

What they're looking for here is to measure the fine-structure constant (alpha), and the huge gravity of the white dwarf, 30,000 times that on Earth, provides an environment in which that constant could be different to Earth.

The suggestion that alpha might differ arises from attempts to resolve general relativity (which deals with the big picture of gravity) with particle physics' Standard Model, using a theory of scalar fields. Here, The Register will rely on the university's statement for further explanation:

“This idea that the laws of physics are different in different places in the cosmos is a huge claim, and needs to be backed up with solid evidence”, says Dr Julian Berengut of the UNSW School of Physics. “By measuring the value of alpha near the white dwarf and comparing it with its value here and now in the laboratory we can indirectly probe whether these alpha-changing scalar fields actually exist.”

Dr Berengut's team is observing the absorption spectra of iron and nickel ions in the atmostphere of white dwarf G191-B2B. In spite of the huge gravity, the stars' radiation stops the ions being sucked down. The absorption spectrum provides the observational tool to measure alpha in the region of the ions.

So far, the work has demonstrated that if there is a change in alpha, it's “smaller than one part in ten thousand”, he said. The group now wants to refine its measurements to detect variations within one part per million – enough to “determine whether alpha is a true constant of nature, or not.” ®

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