19 Feb 2010
Queen's astronomer Professor Alan Fitzsimmons and recent PhD graduate Dr. Sam Duddy are part of an international team that has been awarded over 80 nights at the European Southern Observatory to investigate the changing spin of asteroids.
The ability of asteroids to change the length of their day was only proved in 2007, by a team of astronomers lead by Queen's scientists. It is due to the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect, a force caused by sunlight heating up an irregularly shaped asteroid.
The YORP-effect can cause the asteroid to spin faster or slower and change its spin-axis orientation, explaining many observed phenomena in asteroidal science, such as the creation of binary asteroids. It also affects how the asteroid orbit changes, possibly moving it from a present-day safe path around the Sun to one that might impact the Earth in the far future.
“The precise speed at which YORP spins up and slows down will depend on the size, shape and current orientation.” explained Prof. Fitzsimmons. “It's a very small and difficult to measure effect over a human lifetime, but over tens or hundreds of thousands of years it can have dramatic consequences for the asteroid.”
To investigate this process in detail, the team have been given an astounding 72 nights on the 3.6m New Technology Telescope (NTT) and over 100 hours on the Very Large Telescope (VLT), to measure precisely the spin-rate of the asteroids, detect the tiny changes in period (a few microseconds per year), and measure the physical properties of the asteroids in detail.
In total four asteroids have been seen to exhibit the YORP effect, but uncertainties remain in predicting the magnitude of the effect. This programme, led by Dr. Stephen Lowry (University of Kent), is to monitor the spin rates of a large sample of near-Earth Asteroids with sizes from a few hundred metres to several km. Such a large sample will provide valuable constraints on asteroid surface and shape evolution models as well as models of spin-orbit interactions.
Astronomers in the Astrophysics Research Centre at Queen's will be spearheading the effort to measure the spectra of the asteroids to determine their composition, and also assisting in measuring the precise spin periods.
Prof. Fitzsimmons said “We're starting the observing programme in April, when I'll be spending 3 nights in at the ESO La Silla Observatory in Chile making the first observations. We can't wait to get started.” Team members include: Dr. Stephen Lowry (University of Kent); Professor Alan Fitzsimmons and Dr Samuel Duddy (Queen's University of Belfast); Dr Simon Green, Dr Stephen Wolters and Ben Rozitis (Open University); Dr Colin Snodgrass (Max Planck Institute for Solar System Research, Germany); and Dr Paul Weissman and Dr Michael Hicks (NASA's Jet Propulsion Laboratory, California, USA).