Quasars provide new galactic insights

05 July 2011

The Milky Way.

The Milky Way.
NASA image.

Scientists will be able to measure points on Earth much more accurately following analysis of data which confirms the movement of our solar system in relation to the centre of the Galaxy.

Since 1728, after pioneering work by astronomer James Bradley to verify Earth's passage around the Sun, it has been confirmed that the solar system also rotates around the Galaxy at a velocity of 250 kilometres per second which creates a phenomenon known as secular aberration drift. The phenomenon is caused by the centrifugal acceleration of the solar system resulting from the gravitational attraction of the central point of the Galaxy.

Using sophisticated data analysis equipment and observations of distant extragalactic radio sources, or quasars, scientists have been able for the first time to determine the degree of this long term, or secular aberration drift to be 6.4 microarc seconds per year. This translates to 0.1 millimetres a year on the Earth's surface.

Geoscience Australia scientist, Dr Oleg Titov, says the secular aberration drift has been confirmed through data obtained from a network of more than 50 radio telescopes located around the planet and extending from the archipelago of Svalbard off Norway to Antarctica.

Dr Titov said that, because the distance to the quasars is so extensive, their own peculiar motion can be neglected when analysing the solar system's motion as it moves within the Galaxy.

"By observing the quasars through Very Long Baseline Interferometry, it is possible to detect the secular aberration drift," Dr Titov said.

"Previous attempts to detect this effect were unsuccessful because of insufficient data, but with around five million observations from 555 distant radio sources over more than 30 years, a highly accurate result has been achieved.

"By incorporating the resulting secular aberration drift of 6.4 microarc seconds per year, any calculations associated with a position on Earth and space navigation will be significantly enhanced," Dr Titov said.

As part of a multidisciplinary research and observation program by Geoscience Australia, Dr Titov's work is aimed at improving the accuracy of Australia's National Geospatial Reference System which is a coordinate system, or reference frame, within which measurements of position are made using sets of tools and computer applications. The work is expected to improve the accuracy of the national geospatial reference systems over a 10 year period so that advantage can be taken of the improvements being offered by satellite navigation systems.

"Discovery of the effect will improve the precision of the fundamental reference frame for numerous applications, including terrestrial positioning with satellite based global positioning systems in areas as diverse as agricultural, engineering, transport and emergency management activities as well as in mapping continental drift and movements along fault lines," Dr Titov said.

"This level of detail will provide opportunities also to improve observations of the slight variations associated with climate change, such as in sea level rise," Dr Titov said.

A detailed paper by Dr Titov is available in Astronomy & Astrophysics.

Topic contact: media@ga.gov.au Last updated: October 4, 2013