Liquid mirror telescope sees first light in India

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Top view of the ILMT showing the liquid mercury mirror covered by a thin mylar film. Credit: ARIES, Department of Science and Technology, India

A new telescope with a liquid mirror has seen its first light atop the Himalayan mountains of India. It is the first liquid mirror telescope in the country and the largest in Asia.

Built by astronomers from India, Belgium and Canada, the instrument employs a four-metre-diameter rotating mirror made up of a thin film of liquid mercury to collect and focus light. 

The International Liquid Mirror Telescope (ILMT) is located at an altitude of 2,450 metres at the Devasthal Observatory campus of Aryabhatta Research Institute of Observational Sciences (Aries), an autonomous institute under the Department of Science and Technology in Uttarakhand.

The mirror was created by spinning a pool of mercury, a reflective liquid, so that the surface curved into a parabolic shape ideal for focusing light.

The reflected light passes through a complex multi-lens optical corrector that produces sharp images over a wide field of view. A large-format electronic camera located at the focus records the images. A thin transparent film of mylar protects the mercury from wind. 

The telescope will help in surveying the sky, making it possible to observe several galaxies and other astronomical sources just by staring at the strip of sky that passes overhead. 

The rotation of the earth causes the images to drift across the camera, but this motion is compensated electronically by the camera. This mode of operation increases observing efficiency and makes the telescope particularly sensitive to faint and diffuse objects.

ILMT is the first liquid-mirror telescope designed exclusively for astronomical observations installed at the Devasthal Observatory, which now hosts two four-metre class telescopes – both being the largest aperture telescopes available in the country. 

Big Data and artificial intelligence/machine learning algorithms will be implemented for classifying the objects observed with the ILMT. ‘I am hopeful that this project will attract and motivate several young minds from scientific and engineering backgrounds to take up challenging problems,’ said Professor Dipankar Banerjee, director, Aries.

In the future, several young researchers will be working on different science programmes using the data generated by the project

When regular science operations begin later this year, the ILMT will produce about 10GB of data every night, which will be quickly analysed to reveal variable and transient stellar sources,’ said Dr Brajesh Kumar, ILMT project scientist at Aries. 

‘The data collected from ILMT will be ideally suited to perform a deep photometric and astrometric variability survey over a period of typically five years,’ added project director Professor Jean Surdej (University of Liège, Belgium and University of Poznan, Poland).

The ILMT collaboration includes researchers from Aries in India, the University of Liège and the Royal Observatory of Belgium in Belgium, Poznan Observatory in Poland, the Ulugh Beg Astronomical Institute of the Uzbek Academy of Sciences and National University of Uzbekistan in Uzbekistan, the University of British Columbia, Laval University, the University of Montreal, the University of Toronto, York University and the University of Victoria in Canada. The telescope was designed and built by the Advanced Mechanical and Optical Systems (AMOS) Corporation and the Centre Spatial de Liège in Belgium. 

Robert Smith is a professor at the University of Alberta and historian to JWST since 2002

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Robert Smith is a professor at the University of Alberta and historian to JWST since 2002

01 August 2022