Contact information

Dr. Holger Pletsch
Independent Research Group Leader
Phone:+49 511 762 17171Fax:+49 511 762-2784

Albert Einstein Institute Hannover

Prof. Dr. Bruce Allen
Phone:+49 511 762-17148Fax:+49 511 762-17182

Albert Einstein Institute Hannover

Press contact

Dr. Benjamin Knispel
Dr. Benjamin Knispel
Press Officer AEI Hannover
Phone:+49 511 762-19104Fax:+49 511 762-17182

Albert Einstein Institute Hannover


This animation illustrates how analysis of Fermi data reveals new pulsars. Fermi's LAT records the precise time and position of the gamma rays it detects, but to identify a pulsar requires additional information -- its position in the sky, its pulse period, and the way the pulse changes over time. Additionally, even Fermi's sensitive LAT detects few gamma rays from these objects -- as few as one photon per 100,000 rotations. The Hannover team used new methods to execute a so-called blind search, using computers to check many different combinations of position and period against the 8,000 photons Fermi's LAT has collected during its three years in orbit. When photons from the pulses align in time, a new gamma-ray pulsar has been discovered.
© AEI/NASA Goddard Space Flight Center

Data analysis

When analysing data from gravitational wave detectors, scientists have to rely on very effective algorithms and high computing power. This is necessary, because a possible gravitational wave signal would be scarcely stronger than the background noise at the current measurement accuracy.

Within the LIGO-Virgo Science Collaboration (LVC), which also includes the German-British GEO600 detector in Ruthe near Hanover, all detector data are collected jointly, archived and made available for analysis. Several copies of around 500 Terabytes of data are stored at different computer cluster locations. When the detector network is running, one megabyte of data is generated every second. The largest and most powerful computing cluster is ATLAS at the AEI in Hanover. It has a peak computing power of 64 TFLOP/s (floating-point operations per second).

The data is analysed in several steps. First, the astrophysicists scan large areas of the sky for signals. If there is a conspicuous signal in one direction, they investigate the vicinity with an algorithm which has a narrower search grid and thus requires more computing time. If the signal is confirmed, the scientists analyse its temporal characteristic and examine whether it can be assigned to a specific pulsar period, for example. The Hanover scientists have modified the algorithm to search for continuous sources of gravitational waves and used it successfully to search for gamma-ray pulsars in Fermi data.


This project for distributed volunteer computing connects PC users from all over the world, who voluntarily donate spare computing time on their home and office computers. It has more than 320,000 participants and is therefore one of the largest projects of this kind. Scientific supporters are the Center for Gravitation and Cosmology at the University of Wisconsin-Milwaukee and the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, Hanover) with financial support from the National Science Foundation and the Max Planck Society. Since 2005, Einstein@Home has examined data from the gravitational wave detectors within the LIGO-Virgo-Science Collaboration (LVC) for gravitational waves from unknown, rapidly rotating neutron stars.

As of March 2009, Einstein@Home has also been involved in the search for signals from radio pulsars in observational data from the Arecibo Observatory in Puerto Rico and the Parkes Observatory in Australia. Since the first discovery of a radio pulsar by Einstein@Home in August 2010, the global computer network has discovered more than 40 new radio pulsars. A new search for gamma-ray pulsars in data of the Fermi satellite was added in August 2011; the project is looking for, among other things, the first millisecond pulsar, visible only in the gamma-ray range.

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