Sometimes there is Smoke without Fire

…Or at least, not always the fire you’re looking for. So, as suspected for several months now, the signal seen by the BICEP2 experiment and dubbed “a smoking gun” type of direct evidence for cosmic inflation (for which we have lots of strongly suggestive indirect evidence, by the way) is likely an artefact of the effects of galactic dust. I spoke about this in a post a while back, so I won’t repeat myself here. What everyone has been waiting for has been the results of a joint analysis between the BICEP2 people and the ESA’s Planck mission. The Planck satellite, you may recall from reading here or elsewhere, is also designed to carefully study the polarisation of the cosmic microwave background (the earliest light to shine in the universe), and so can (through thorough analysis of the effects of dust that it has measured independently) help rule in or out whether there is a signal. Planck studies essentially the whole sky, not just the patch that BICEP2 was carefully looking at, and one of the nice images released was Planck’s view of the patch of sky that BICEP2 sees. It is the image you see above. (Image credit** and explanation here.) Well, the results of all the analysis were announced last week and now it seems to be confirmed that what BICEP2 saw is not distinguishable from the effects of galactic dust. So, onwards and upwards.

But wait. There’s much more to Planck’s recent announcements of news than just pouring much needed cold water on a hotly reported result. There are reports on several new pieces of work from their own agenda of things to study, including the realisation that the earliest stars to shine in the universe may have started doing so later than previously thought. This turns out to be helpful in resolving a number of puzzles in early universe cosmology. I recommend reading more about all this and more by following links from their news page.

-cvj

**Image: ESA/Planck Collaboration. Acknowledgment: M.-A. Miville-Deschênes, CNRS – Institut d’Astrophysique Spatiale, Université Paris-XI, Orsay, France