Liquid mirror telescope in Devasthal sees first light

June 3, 2022

In News:

A new telescope facility atop a mountain in the Himalayan range will now keep a watch on the overhead sky to identify transient or variable objects such as supernovae, gravitational lenses, space debris, and asteroids.

What’s in today’s article:

What is a Liquid Mirror Telescope (LMT)?

A liquid mirror telescope, as its name suggests, uses a liquid, not aluminized glass, as its primary mirror.
The liquid, usually mercury, is poured into a rotating dish.
The rotation creates two fundamental forces that act on the mercury -- gravity and inertia.
Gravity pulls down on the liquid surface, while inertia pulls the liquid sideways at the edge of the dish.
As a result, the liquid forms a uniform and perfect parabola, the ideal reflecting surface for a telescope.
Best of all, the liquid mirror surface remains smooth and flawless with little or no maintenance.
If the liquid is disturbed, gravity and inertia will act on the liquid to return it to its original state.

History of LMT:

Ernesto Capocci, an Italian astronomer, was the first person to describe how an LMT might work in 1850.
He conceived of the idea after reading about experiments, conducted by Isaac Newton and others, involving spinning liquids.
In the early 20th century, the American physicist W. Wood actually built what Capocci had described 50 years earlier.
Wood's LMT featured a one-centimetre layer of mercury placed in a rotating dish.
He was able to observe the moon but noted that the image was distorted.
Modern astronomers learned that the image quality of an LMT was greatly improved if a thinner layer of mercury was used, so today's LMTs use a one-millimetre layer of mercury.

How is LMT different from Optical Telescope?

An optical telescope is a telescope that gathers and focuses light mainly from the visible part of the electromagnetic spectrum, to create a magnified image for direct visual inspection, to make a photograph, or to collect data through electronic image sensors.
Unlike optical telescope, an LMT remains stationary as it cannot be turned and pointed in any direction.
It “stares” at the zenith and watches the sky as the Earth rotates, thereby giving a view of different objects.

News Summary:

India’s first liquid-mirror telescope, which will observe asteroids, supernovae, space debris and all other celestial objects from an altitude of 2,450 metres in the Himalayas, has seen its first light.
It has now entered the commissioning phase and will start scientific observations by October, 2022.
It is established on the campus of the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES) in Nainital, Uttarakhand.
Known as the International Liquid Mirror Telescope (ILMT), it is the only liquid-mirror telescope operational anywhere in the world.
It will also hold the unique tag of being the maiden liquid-telescope globally to be designed exclusively for astronomical purposes.

Why India’s majority telescopes are stationed at Devasthal Observatory?

ILMT will be the third telescope to be operating from Devasthal after the –
- 6-metre Devasthal Optical Telescope (DOT) — the largest in India commissioned in 2016 and
- 3-metre Devasthal Fast Optical Telescope (DFOT) inaugurated in 2010.
Devasthal Observatory is the result of collaborative work between astronomers from ARIES and astronomical institutions from across the world.
- Aryabhatta Research Institute of Observational Sciences (ARIES) is an autonomous institute under the Department of Science & Technology.
This site was chosen after an extensive site characterization conducted during 1980 - 2001 in the central Himalayan range.
The main advantages of Devasthal site are in its dark skies, sub-arcsec seeing, low extinction and at the same time being easily assessable and manageable.
In total, 41,692 square meter of land has been transferred to ARIES from Uttarakhand Government which includes roads, base camp area and telescope site.

See All