The Astrophysics Group at the Cavendish hosts one of the world's leading teams developing aperture synthesis methods (originally derived for use in radioastronomy) at optical and infrared wavelengths. These allow imaging at the diffraction-limit, i.e. overriding the effects of atmospheric fluctuations which usually restrict the angular resolution attainable from the ground to of order a second of arc. There are two main strands to this activity:

• Work with single telescopes

  We continue to exploit aperture synthesis and other methods at a number of the world's largest optical and infrared telescope to realise diffraction limited images without recourse to adaptive optics. Studies such as these are being used to explore, for example, surface activity on supergiants, the structure and origin of the dust envelopes of AGB stars and planetary nebula progenitors, and the populations of crowded stellar clusters.

• Work with separated element interferometers - COAST

  In parallel with this our group operates an interferometric array of five telescopes with baselines of up to 100m. This telescope, the Cambridge Optical Aperture Synthesis Telescope (COAST), was developed in the 1990's as the world's first optical synthesis array. It is currently one of only two arrays worldwide that allow imaging of astronomical sources and has already produced maps with an angular resolution some 25 times better than the Hubble Space Telescope. It is now being used for a range of astronomical programmes including searches for close stellar companions, direct measurements of stellar pulsation, imaging of the surfaces of nearby evolved stars, and studying the structures of ejected hydrogen disks in hot stars.

  Experience with COAST is also being used to refine the design of a next-generation facility array (LOA). This would aim to deliver sub-milliarcsecond imaging at high sensitivity. Our activity includes feasibility studies of such an array and its subsystems as well as the design and testing of prototyping hardware at COAST for use in LOA and other modern arrays such as ESO's Very Large Telescope Interferometer.

The COAST Homepage

Last Modified 27 November 2001
Please send comments to Chris Haniff.