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LOFAR takes the pulse of the radio sky

A powerful new telescope designed and built by ASTRON is allowing an international team of scientists to have their “best-ever look” at pulsars: rapidly rotating neutron stars, created when massive stars die.

Published by the editorial team, 13 April 2011

In the first refereed scientific results from the new European telescope LOFAR (Low Frequency Array), soon to appear in Astronomy & Astrophysics, the scientists present the most sensitive low-frequency observations of pulsars ever made.

The International LOFAR Telescope is the first in a new generation of massive radio telescopes, designed to study the sky at the lowest radio frequencies accessible from the surface of the Earth. Deep observations of pulsars are one of its key science goals.

Lead author on the paper, Dr. Ben Stappers of the University of Manchester (UK), said: “We are returning to the frequencies where pulsars were first discovered, but now with a telescope of a sophistication that could not have been imagined back in the 1960s.”

The chance detection of the first pulsar in 1967 is considered one of the great discoveries in astronomy. Astronomers got their first glimpse of pulsars by using a radio telescope sensitive to frequencies of 81MHz (roughly the same frequency as a commercial FM radio station).

With LOFAR, astronomers have gone back to some of the same techniques used in the first pulsar observations, but have used modern computing and optical fibre connections to increase the power of their telescope many times over. This will allow LOFAR to analyse regular pulses of radio emission and probe such things as the physics of gravity and the properties of the material that pervades our Galaxy.

Dr. Stappers said: “Even though these are just the first test results they are already showing spectacular promise.”

LOFAR uses high speed internet to connect thousands of small antennas spread across Europe. Their signals are sent to a supercomputer in the Netherlands.

The LOFAR telescope has no moving parts, instead relying on adding digital time delays to “point” the telescope in a particular direction. This approach offers a much-greater level of flexibility in the way astronomers can analyse the data. For instance, unlike a conventional radio telescope, it is possible to point in multiple directions simultaneously simply by having the supercomputer crunch more data.

For astronomers who want to search for new pulsars, this means they can scan the sky much more quickly.

Dr. Jason Hessels from ASTRON said: “A traditional radio telescope is limited to viewing a very small fraction of the sky at any one time. LOFAR casts a much broader net, which is going to help us discover new pulsars and detect explosions that were too rare to catch with past telescopes.”

The team’s next step is to harness LOFAR’s capabilities to address some of the long-standing mysteries about how pulsars shine and also to discover nearby pulsars that were missed by past telescopes. “LOFAR has the potential to find all the undiscovered pulsars in the neighbourhood of the Sun and to reveal rare explosions in our Galaxy and beyond. We’re very excited to see what’s out there.” says Dr. Joeri van Leeuwen from ASTRON.

LOFAR is capable of detecting radio waves over a very large range of frequencies, all the way from 10MHz to 240MHz. As well as searching for pulsars, LOFAR will be used for making deep radio images of galaxies, studying the early history of the Universe, and for monitoring the activity of the Sun and planets. LOFAR is also an important technological step towards the planned, next generation radio telescope the Square Kilometre Array (SKA).

For more information, please contact:

Femke Boekhorst, PR & Communication. Tel.: +31 521 595 204. E-mail:

Dr. Joeri van Leeuwen, astronomer. Tel.: +31 6 26154552 and +31 521 595 770. E-mail:

Dr. Jason Hessels, astronomer. Tel.: +31 6 10260062. E-mail:

The full article with the new results can be found here:


Because of its unique design, LOFAR can observe in many different directions simultaneously. For this image, five pulsars, spread over the entire sky, were observed simultaneously. Credits: Tom Hassall/U.Man./ASTRON.

More information about ASTRON:


More information about LOFAR:
The International LOFAR telescope is a European collaboration, led by ASTRON Netherlands Institute for Radio Astronomy. By combining thousands of simple antennas with a powerful supercomputer, LOFAR can observe large parts of the sky very fast in different directions simultaneously on relatively unknown low frequencies. This opens up a new window to the universe for astronomers. See also:



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