Some of the sharpest and deepest images of astronomical objects ever seen will be revealed at the National Astronomy Meeting in Guernsey next week. The images were taken by the UK infrared telescope, in Hawaii. Ingenious astronomers have added an instrument called the 'Fast Track Imager'.

Project scientist, Dr Patrick Roche, comments "It is very exciting to see the exquisite images now being obtained at UK Infrared Telescope at the culmination of the image quality improvement programme. "Under the best conditions, it produces images that are comparable in detail to those provided by the Hubble Space telescope at wavelengths near 2 microns. We are seeing new details in even some of the best-studied objects such as in the star-forming regions in the Orion nebula," added Roche.

By improving the technology of the telescope and adding this Fast Track Imager the UK infrared telescope has become an astronomical facility of unrivalled capability. It outperforms the much more modern and expensive 10-m telescopes in some critical areas of astronomical research.

The telescope now has an active primary mirror whose shape is adjusted by a computer-controlled support structure to maintain optimum performance. An articulated secondary mirror directs the light to the instrument.

The secondary mirror is moved slowly in 3 axes to ensure that the focus and alignment of the telescope mirrors is tracked accurately while fast motions in two additional axes compensate for wind buffeting of the telescope and some of the effects of atmospheric turbulence. This steadies the images of stars and galaxies transmitted to the instrument.

Astronomer, Andy Adamson (UKIRT) explains "This is an amazing feat for a telescope that was designed during the 1970s as a cheap but effective 'flux collector' to deliver infrared light to what today seem primitive instruments to analyse stars and galaxies".

The first images taken with the new instrument show the star formation cloud in Orion (visible quite clearly in the winter skies in the northern hemisphere). It is a site of recent star formation about 1500 light years away within our own Galaxy.

The violent nature of processes by which stars are born is evident in the "bullet-like" flows of shocked gas away from the central cluster. One of the most exciting - and still not fully understood - discoveries in astronomy in the past decade has been the realization that the process of forming stars like the Sun almost always gives rise to large outward flows of gas. In other regions, the stars form in a much more individualistic way; HH7-11 is such a region.

The beautiful colours of the Mon R2 star-formation region are revealed by "true-colour" infrared imaging with UFTI. These objects are largely inaccessible to telescopes using visible light; only the infrared penetrates the clouds of dust within which such objects form.

Finally, a distant cluster of galaxies - Abell 851 - is shown as an example of the synergy between the 4-metre UKIRT and the 10-metre Keck telescope (also situated on the peak of Mauna Kea).

This picture combines imaging at short infrared (I band) from the Keck telescope and true infrared (K band) from UFTI on UKIRT to give an impression of the colour differences in this cluster of galaxies at prodigious distance from us.

This image takes advantage of the finite speed of light to observe galaxies as they were billions of years ago, and to study the evolution of galaxies over cosmic timescales.

Technical Notes

The Fast Track imager detects infrared light with wavelengths between 0.8 and 2.5 microns (2 to 6 times longer than that of blue light, and comprises the near-infrared portion of the electromagnetic spectrum just beyond the wavelengths to which the human eye is sensitive).

Observations at these infrared wavelengths are especially important to astronomers because: infrared light is relatively unattenuated by interstellar dust, and so can be detected from e.g. stars forming in dusty regions which are hidden at visible wavelengths.

Also the visible light from the most distant galaxies is redshifted to a degree which means that it can only be observed by us at infrared wavelengths.

Important molecular species (including the most common molecule in the universe, H2) and dust particles emit at near-IR wavelengths. This allows us to look at the building blocks of planets and complex molecules that are essential to the development of life; and cool stars and planets shine most strongly at infrared wavelengths.

Fast Track Imager

The Fast Track Imager was constructed in the Physics Department at Oxford University in a collaboration with the Royal Observatory Edinburgh, the institute of Astronomy, Cambridge and the Joint Astronomy Centre, Hawaii. The project was led by Dr Patrick Roche at Oxford, and the instrument was funded by the Particle Physics and Astronomy Research Council through a contract with the Joint Astronomy Centre, Hawaii. The total cost of the instrument was 450,000 pounds.

The instrument is cooled to 70 K (-200 C) by a closed-cycle helium refrigerator and is now mounted permanently on the UKIRT, where it is available for use by UK astronomical research teams. The instrument uses the latest infrared detector from Rockwell Corporation.

It has more than 1 million infrared-sensitive elements bonded to a silicon readout array, to provide high-definition images. Under the best conditions, the images obtained have a resolution of better than 0.25 seconds or arc (or 1/7200 the diameter of the moon).

This compares with an accepted norm of about 1 arcsecond for the resolution of ground-based telescopes up to the 1980s. The sensitivity of most observations depends on the light collected (which is proportional to the square of the telescope diameter), divided by the image size.

For observations of stars and other point-like objects, a 4-m diameter telescope with 0.25 arcsecond images can be competitive with a significantly larger telescope with poorer image quality.

Mauna Kea on Hawaii is the best site for infrared astronomy. The 14000 foot high volcano surrounded by the Pacific ocean, protrudes above a significant fraction of the Earth*s atmosphere (the pressure at the summit is only 60% of that at sea-level).

The air above the telescopes is unperturbed by continental weather patterns and is dry and cold (typical temperatures are close to freezing) leading to ideal conditions for astronomy.

A greater fraction of the infrared light from planets and their moons, interstellar gas clouds, stars and galaxies reaches the ground here than at virtually any other observatory site in the world.

Mauna Kea is host to several of the worlds most powerful telescopes including the UK Infrared Telescope, the James Clerk Maxwell mm-wave telescope, and the new 8-m Gemini telescope.

The UK Infrared Telescope and the development of the fast track imager are funded by the Particle Physics and Astronomy Research Council. Images at Particle Physics and Astronomy Research Council.

Space Science - SpaceDaily Special Report

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