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| PRI (MPIfR) 06/2010 (5) | Press Release | June 24, 2010 |
An international team of astronomers, including Michael Kramer
from the Max-Planck-Institut für Radioastronomie (Bonn, Germany)
has studied the behaviour of
natural cosmic clocks
and discovered a way to potentially turn them
into the best time keepers in the Universe. The scientists made their
breakthrough using decade-long observations from the 76-m Lovell radio
telescope at the University of Manchester's Jodrell Bank Observatory
to track the radio signals of an extreme type of star known as
a pulsars.
This new understanding of pulsar
spin-down could improve the chances to use the fastest spinning pulsars
in order to make the first direct detection of ripples, known as
gravitational waves, in the fabric of space time.
Figure 1:
Schematic view of a pulsar. Pulsars provide the
most precise natural cosmic clocks known to date.
A click onto the image gives an animation (MPG file) showing
pulses in two different states of the pulsar.
Pulsars appear to be able to switch between those states which differ
by the amount of charged particles flowing from the surface to outer space.
This change in current is visible in a change of slow-down in their rotation,
such that the pulsar 'brakes' faster when the currents are large and 'brakes'
less fast when the currents are weak.
Image & Animation: M. Kramer, MPIfR.
Radio pulsars have been studied in detail since their discovery in 1967 and their exquisite rotational stability has led to the discovery of the first extra-Solar planets and provided tests for our theories of the Universe. However, the rotational stability is not perfect and, until now, slight irregularities in their rotation has significantly reduced their usefulness as precision tools.
The team, led by Professor Andrew Lyne, have used observations from the Lovell telescope to explain these variations and to demonstrate a method by which they may be corrected. Professor Lyne explains: "Mankind's best clocks all need corrections, perhaps for the effects of changing temperature, atmospheric pressure, humidity or local magnetic field. Here, we have found a potential means of correcting an astrophysical clock".
The rate at which all pulsars spin is known to be decreasing very slowly. What the team has found is that the deviations arise because there are actually two spin-down rates and not one, and that the pulsar switches between them, abruptly and rather unpredictably. Dr George Hobbs describes the team's second vital discovery "that these changes are associated with a change in the shape of the pulse, or tick, emitted by the pulsar. Because of this, precision measurements of the pulse shape at any particular time indicate exactly what the slowdown rate is and allow the calculation of a "correction". This significantly improves their properties as clocks."
As stated by Professor Michael Kramer: "These results give a completely new insight into the extreme conditions near neutron stars and offer the potential for improving our already very precise experiments in gravitation". Michael Kramer, director at the Max-Planck-Institut für Radioastronomie and head of the research group "Fundamental Physics in Radio Astronomy" is this years recipient of the research award of the Berlin-Brandenburg Academy of Sciences for his contributions to the research of neutron stars.
It is hoped that this new understanding of pulsar spin-down will improve the chances that the fastest spinning pulsars will be used to make the first direct detection of ripples, known as gravitational waves, in the fabric of space time. As reported by Professor Ingrid Stairs "Many observatories around the World are attempting to use pulsars in order to detect the gravitational waves that are expected to be created by supermassive binary black holes in the Universe. With our new technique we may be able to reveal the gravitational wave signals that are currently hidden because of the irregularities in the pulsar rotation."
Figure 2:
The Lovell telescope,
with a diameter of 76 m still the third-largest
fully-steerable telescope in the world.
The decade-long pulsar observations described here were performed with
the Lovell telescope.
Foto: Jodrell Bank Centre for Astrophysics, University of Manchester.
Switched magnetospheric regulation of pulsar spin-down
,
Andrew Lyne, George Hobbs, Michael Kramer, Ingrid Stairs, Ben Stappers
2010, Science Express, DOI: 10.1126/science.1186683
Animation (MPG File) of pulses in two different pulsar states (cf. Fig. 1). Graphics: M. Kramer, MPIfR.
Max Planck Institute for Radio Astronomy (MPIfR).
Fundamental Physics in Radio Astronomy Group at MPIfR.
Jodrell Bank Centre for Astrophysics
.
Cosmic clocks hold the key to the secrets of the Universe, Jodrell Bank Press Release, June 23, 2010.
Astronomers find cause of "dicky tickers", CSIRO Media Release, June 24, 2010.
Akademiepreis für Michael Kramer (in German), Pressemitteilung der Berlin-Brandenburgischen Akademie der Wissenschaften vom 22. Juni 2010.
Telescope link up will shed more light on extreme stars, Jodrell Bank Press Release, April 22, 2010.
Eine Schwarze Witwe im Reich der Sterne
(in German),
PRI (MPIfR) 02/2010 (1), February 19, 2010.
Prof. Dr. Michael Kramer,
Director and Head of Research Group "Fundamental Physics in Radio Astronomy",
Max-Planck-Institut für Radioastronomie, Bonn.
Phone: +49-228-525-278
E-mail: mkramer (at)
mpifr.de
Prof. Dr. Andrew Lyne,
Jodrell Bank Centre for Astrophysics,
University of Manchester, UK.
Fon: +44 1477 572640
E-mail: andrew.lyne
(at) manchester.ac.uk
Dr. Norbert Junkes,
Public Outreach,
Max-Planck-Institut für Radioastronomie, Bonn.
Phone: +49-228-525-399
E-mail: njunkes (at)
mpifr.de