Date: 10/10/2022

Relevance: GS-3: Science and Technology- developments and their applications and effects in everyday life.

Key Phrases: Indian Astronomical observatory, Hanle Dark Sky Reserve (HDSR), High Altitude Gamma Ray Telescope (HAGAR), Himalayan Chandra Telescope (HCT), Major Atmospheric Cherenkov Experiment Telescope (MACE)

Context:

• Recently, the Department of Science & Technology (DST) has announced the setting up of India’s first Dark Sky Reserve in Hanle, Ladakh.

Indian Astronomical observatory : Historical background

• Indian astronomers in India, led by R. Rajamohan, discovered an asteroid that was later named 4130 Ramanujan.
  • It was the first time in 104 years that asteroids were discovered from India.
• They carried out these discoveries using the 45-cm Schmidt telescope, which was housed on the Javadi hills in Kavalur, Tamil Nadu and the spot is today called as Vainu Bappu Observatory.
• The Vainu Bappu Observatory was situated at 750 metres above sea level, located amid a forest and offered fairly unobstructed vistas of the night sky making it suitable for an observatory.
• Although Kavalur’s geography put it in the path of both (South-west and North-East) monsoonal clouds forcing the observatory to often shut down for months
  • Rain clouds absorb starlight and radiation from cosmic objects, preventing them from being caught on the telescopes of cameras.
  • Hence, the search began in the early 1980s for a place least affected by the monsoon.

Suitable conditions for an Astronomical observatory

• It should catch the faintest of stars’ radiation that often lie outside the range of visible light.
  • It is necessary to be able to detect stars or traces of cosmic phenomena, such as supernovae or nebulae from light years away.
• Dry atmosphere is preferred because such radiation is easily absorbed by water vapour and so a telescope high above ground where the atmosphere is drier is helpful.
  • A dry, high-altitude desert is in many ways the ideal location
  • Such terrain is difficult and quite inaccessible.
  • After several expeditions and teams to different parts of the Himalayas and finally Hanle, Ladakh was chosen as it provides the ideal conditions.

The Hanle Astronomical observatory

• Geography and Climatic conditions
  • The Indian Astronomical Observatory (IAO) stands on the mountain called Digpa-Ratsa Ri, aka Mt Saraswati, Hanle in south-eastern Ladakh union territory at an altitude of 14,000 ft above sea level.
  • Hanle site is as dry as the Atacama Desert in Chile and much drier than Devasthal (Uttarakhand) and has around 270 clear nights in a year.
• Observatory Set-up
  • The IAO at Hanle has one of the world's highest sites for optical, infrared and gamma-ray telescopes.
  • According to the Department of Science and Technology the setup will give best results because it has some advantages such as
    • Clear nights
    • Minimal light pollution
    • Background aerosol concentration
    • Extremely dry atmospheric condition
    • Uninterrupted monsoon
  • Such conditions are considered crucial for astronomers to build huge telescopes and plan for future observatories and predict how they will vary with time.
• The MACE Telescope
  • The 21 meter diameter telescope at IAO is called the Major Atmospheric Cherenkov Experiment Telescope (MACE)
  • It is currently the ninth highest optical telescope in the world and is operated by the Indian Institute of Astrophysics, (IIA) Bangalore.
  • The goal of MACE is to detect Cherenkov radiation from space.
    • Cherenkov radiation is a special kind of light from gamma rays, or the most energetic sources of radiation, that can result from dying stars or several galactic events.
• Other important telescopes and equipment at the IAO
  • High Altitude Gamma Ray Telescope (HAGAR): It is an array of seven telescopes, operational since September 2008 and constitutes the first phase of the Himalayan Gamma-Ray Observatory (HIGRO) project.
    • It also looks at Cherenkov radiation, although at a lower range of energies.
  • Himalayan Chandra Telescope (HCT): It is the metallic capsule, the highest of the observatories, the oldest and active since 2000.
    • An optical-infrared telescope with a 2-metre lens, designed to detect light from the visible range of the electromagnetic spectrum as well as that just below it, or the infra-red spectrum.
    • The second capsule, situated slightly lower than the HCT, is the GROWTH-India telescope, a 70-cm telescope made by IIA and IIT Mumbai is equipped to track cosmic events, such as afterglows of a gamma ray burst or tracking the path of asteroids.
• Operations
  • The IAO telescopes, however, can be controlled remotely via a satellite link.
  • Irrespective of weather, the astronomers at the IIA’s Centre for Research and Education in Science and Technology (CREST), Bengaluru can manoeuvre the HCT to face their desired spot of sky.
  • The other instruments too are equipped to be remotely controlled.
• Significance of the IAO
  • The IAO provides a platform to observe a range of cosmic phenomena and investigate the mysteries of the universe.
  • Owing to a wide span of frequencies covered collectively, the IAO provides multiple advantages.
  • Telescopes with small diameters generally can track a greater swath of sky but those with larger diameters can peer deeper when trained towards desired locations.
• Recent developments
  • In recent years, these telescopes have helped gain a better understanding of a system of Earth-sized planets orbiting the TRAPPIST-1 star, about 40 light years away from Earth, as well as gravitational waves that resulted from the collision of neutron stars from a billion years ago.

Amidst the bright lights challenges are many

• High Altitude and adverse weather
  • Atmospheric oxygen is low, making one prone to mountain sickness.
  • Desiccated air translates to sub-zero winters for at least six months of the year.
  • Cold, windy nights, and with no access to the electric grid from April to Sep.
• Light pollution
  • Artificial light from cities and home electrification have obscured the natural night sky and for astronomy, the artificial sources of light are contaminants.
  • Recent studies show that clouds, the biggest reflectors of sunlight, scatter artificial light from ground-based sources, amplifying light pollution
  • Light beams from vehicles may affect sensors of telescopes and this will lead to inaccuracy of collected data which may result in loss of scientific data.
• There is a dearth of basic infrastructure development in the Hanle and nearby areas.

Conclusion

• The declaration of Hanle as India’s first Dark Sky Reserve is a step in the right direction; it will prevent to a large extent the damage posed by light to the observatory and related research will get a boost.
• The announcement also seeks to provide dark curtains to the locals so that the impact of residential lights is minimized.
• To promote Astro-tourism, villages around Hanle will be encouraged to promote homestays equipped with telescopes that visitors can use to view the night sky.
• Therefore the need of the hour is to take all the stakeholders into the confidence to make it a win-win situation for all involved.

Source: The Hindu

Mains Question:

Q. What do you know about the Indian astronomical observatory? Which types of conditions are required to establish astronomical observatories? What is a dark sky reserve? How can a dark sky reserve help in overcoming challenges faced by astro-scientists and researchers? (250 words).