India’s first liquid mirror telescope is up and running. It’s the first and largest liquid mercury telescope to be built at a high altitude, and if that isn’t impressive enough, it is also the first liquid mirror telescope to be used for astronomy.
A liquid mercury telescope is a kind of telescope that utilizes a spinning bowl of liquid mercury to create the reflective surface of a mirror. When the mercury is rotated at a constant speed, Earth’s gravity causes the surface of the mercury to become a parabola, which is ideal for reflecting light to a point. This telescope holds 50 liters (700 kg) of mercury which spins into a mirror 3.5mm thick.
Dubbed the International Liquid-Mirror Telescope (ILMT), it is located on the Devasthal Observatory campus in India, 2,450 meters above sea level. The $2 million project was a collaboration by India, Belgium, Canada, Poland, and Uzbekistan.
It was designed and built at Advanced Mechanical and Optical Systems Corporation at the Centre Spatial de Liège in Belgium. Even though the mirror is only 4 meters in diameter, the technique of using spinning liquid mercury is much cheaper than traditional mirrors that require more time and manufacturing. In comparison, the Devasthal Optical telescope, a large but more conventional telescope, was built by the same company for $18 million.
The telescope will run for five years straight, looking straight up at a patch of sky about as wide as the moon's diameter. While other telescopes can scan the entire sky, the ILMT has the advantage of observing the same swath of sky for years, allowing astronomers to detect changes in the night sky and image even the faintest objects.
Not only is this telescope the first of its kind on Earth, but it could also be the first on the moon. While Earth’s rotation would warp the parabola mirrors larger than 8 meters, the moon rotates more slowly and could host a wider liquid mercury telescope. However, mercury wouldn’t be a viable material: it’s too heavy to transport, would freeze at night, and evaporate during the day. However, a liquid mirror researcher named Ermanno Borra from Laval University proved that ionic liquids, or ionic compounds with melting points below 100 °C, could be coated with silver for the same effect.
Sources: Indian Express, Science News
