Parkes Pulsar Timing Array
The Parkes Pulsar Timing Array (PPTA) project is a combined effort from astronomers and students across several institutions dedicated to the very first detection of gravitational waves.
The PPTA project was formed in 2004 as a collaboration between CSIRO Astronomy and Space Science and Swinburne University of Technology, and welcomes members from across the globe. The PPTA is now a member of the International Pulsar Timing Array, a global consortium sharing the common goal.
The 64 metre Parkes radio telescope located in Parkes, New South Wales, Australia, is the key instrument in this project, collecting data over many years from an array of fast-spinning stars in our Milky Way Galaxy emitting beams of radio waves, called millisecond pulsars (MSPs).
The PPTA project in brief
The PPTA project aims to fulfill the following goals:
Gravitational waves were predicted by Albert Einstein in 1916, as part of his 'General Theory of Relativity'. He postulated that accelerating massive bodies would create ripples in space and time, stretching and shrinking anything in their path. However the effect is miniscule, for example a wave passing through a dining table would change its length by about the width of a proton!. It is clear that very high precision measurements would be needed in order to detect any such effect. This is where MSPs come in. These stars emit pulses of radio waves in a predictable clock-like fashion, akin to a lighthouse. Astronomers at Parkes can measure the arrival time of these pulses from an array of MSPs dotted around the sky with very high precision, and compare that with the predicted arrival time gained by long-term monitoring of these pulsars. It is thought that if a gravitational wave created by two super-massive black holes about to merge (the most massive objects in the Universe that we know of) were to pass by, it would stretch and shrink the pulses of radio waves in such a way that all the pulsars in the array would show a correlated change in pulse arrival time.
Long-term monitoring of the PPTA pulsars has lead to development of the first pulsar-based timescale with a precision comparable to that of terrestrial timescales. Please see Development of a pulsar-based timescale for more information.
An offshoot of high precision pulsar timing is the ability to locate masses in our Solar System. The PPTA team have attempted to improve the estimates of masses of planets in our Solar system and have derived the most precise published estimate of the mass of the Jovian system. Please see Measuring the mass of solar system planets using pulsar timing for more information.
PPTA data sets provide information not only on arrival times, but the nature of the intrinsic source itself such as pulse variability and timing irregularities. In addition, we can learn about the nature of the interstellar medium (ISM) along the line of sight to the source, and interaction with the Solar wind.
For a more extensive overview of the PPTA project, please see The Parkes Pulsar Timing Array: What we've done and what we're doing, and in more detail including the first PPTA data release in The Parkes Pulsar Timing Array Project.
Our paper announcing a new limit on the strength of the gravitational-wave background and its implication was published in Science. See Gravitational-wave Limits from Pulsar Timing Constrain Supermassive Black Hole Evolution.
Parkes observations are now conducted in full remote mode! We are observing from the Marsfield SOC, and the comfort of our own homes!
How to get involved
The PPTA project welcomes new members to help contribute to this fascinating and expanding area of research.
If you wish to become a member, or are a student who would like to get involved in the research, please contact the team leader George Hobbs, for more information.
If you are interested in learning more about the general principles behind pulsar astronomy, pulsar timing and gravitational waves, please go to our Education & Outreach page.
All PPTA team members may update this page. However, please contact Lawrence Toomey if you feel that major changes are required.