Anomalies in Planck data may stem from faulty collection

Nature : Using data gathered at several different frequencies by the European Space Agency’s Planck spacecraft, researchers earlier this year produced the highest resolution map of the universe’s cosmic microwave background (CMB) radiation. The mapping revealed that matter was denser and more varied in distribution than previously measured. The data also indicated a lower value for the Hubble constant . However, a new analysis of the data by David Spergel of Princeton University and his colleagues suggests that the discrepancies from previous work come from the data collected at a specific frequency—217 GHz. The researchers noted that the original analysis of data at that frequency did not account for some failed instrument calibration tests and appeared to be suspiciously correlated with data gathered at lower frequencies. When they removed the data collected at 217 GHz from the composite map, the discrepancies were no longer present. Spergel suggests that the problem could have been caused by the sensors on Planck being housed together in the same cooling system instead of individually. The team members that originally presented the Planck data have acknowledged the possibility of systematic errors in the data and will reevaluate their work, but they maintain that the discrepancies are still primarily the result of the improved instrumentation on the craft. As with earlier maps of the CMB, Spergel says that continued reanalysis of the Planck data will likely continue to improve the initial mapping.