Indian Astronomical Observatory | Where the stars must not twinkle

Why in News?

• Recently, in a first-of-its-kind initiative, the Department of Science & Technology (DST) has announced the setting up of India’s first Dark Sky Reserve in Hanle, Ladakh.
• The article discusses the challenges in having it declared an International Dark Sky Reserve, the story behind Hanle site discovery and the efforts to make residents stakeholders in the process.

 

About A Dark Sky Reserve

• Description: It is a designation given to a place that has policies in place to ensure that a tract of land or region has minimal artificial light interference.
• Designated areas: These are areas that offer exceptional starry nights and are specifically protected for scientific, natural, educational, cultural, heritage and/or public enjoyment.
• Accreditation: It is designated by the U.S.-based non-profit, International Dark-Sky Association (IDA) since 1988.

 

Background of Indian Astronomical Observatory (IAO)

• Discovery: 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.
• Location: Their instrument, the 45-cm Schmidt telescope, was housed on the Javadi hills in Kavalur, Tamil Nadu and the spot is today called as Vainu Bappu Observatory.
  • It is today run by the Indian Institute of Astrophysics (IIA), Bengaluru, and is among India's foremost observatories.
• Reasoned choice: It was chosen in the 1960s because it was at impressive 750 metres above sea level, located amid a forest and offered fairly unobstructed vistas of the night sky.
• Not ideal spot: Kavalur’s geography put it in the path of both monsoonal clouds, during June-September and the returning, or northeast monsoon in November, forcing the observatory to often shut down for months.
  • Also, rainclouds 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.

 

Conditions for ideal Astronomical Observatory

• Outside visible light range: To be able to detect stars or traces of cosmic phenomena, such as supernovae from light years away, astronomers must be able to catch the faintest slivers of their radiation that often lie outside the range of visible light.
• Dry atmosphere: Such radiation (outside visible light range) is, however, easily absorbed by water vapour and hence a telescope high above ground where the atmosphere is drier was being preferred.

 

Ladakh chosen as Astronomical Observatory

• A dry, high-altitude desert is in many ways was an ideal location, but such terrain is difficult and quite inaccessible.
  • However, after several expeditions to different parts of the Himalayas finally Hanle (Ladakh) was chosen.

 

About Hanle, Ladakh

• Location: The Indian Astronomical Observatory stands on Saraswati, Hanle in south-eastern Ladakh union territory at an altitude of 14,000 ft above sea level .
• Climatic conditions: 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.
• Set-up: The Indian Astronomical Observatory here at Hanle has one of the world's highest sites for optical, infrared and gamma-ray telescopes.
• Optimal conditions: According to the Department of Science and Technology, this is due to its advantages of:
  • Clear nights
  • Minimal light pollution
  • Background aerosol concentration
  • Extremely dry atmospheric condition
  • Uninterrupted monsoon
• Also, such conditions are considered crucial for astronomers to build huge telescopes and plan for future observatories and predict how they will vary with time.
• Global standing: Termed as the Major Atmospheric Cherenkov Experiment Telescope (MACE), located near Hanle, it is currently the ninth highest optical telescope in the world and is operated by the Indian Institute of Astrophysics, (IIA) Bangalore.
  • MACE is built by a consortium of the Bhabha Atomic Research Centre, the Tata Institute of Fundamental Research, the Electronics Corporation of India Ltd. and the IIA.
  • The goal of MACE is to detect Cherenkov radiation from space.
  • This 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.

 

The Observatory has other active telescopes namely as follows:

• Himalayan Chandra Telescope (HCT): It is the metallic capsule, the highest of the observatories, the oldest and active since 2000 .
  • It is 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.
• A 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.
• Functioning 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: Owing to wide span of frequencies covered collectively, the IAO provides multiple vantage points to observe a range of cosmic phenomena and investigate the mysteries of the universe.
  • 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.

 

Concerns

• 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
• Demonstration: For instance, the light from high beam of a vehicle at night would flood the sensors of the telescope.
  • Separating this light from that collected as part of experiments is a cumbersome process and results in loss of scientific data.
• Infrastructure development: Hanle, as it currently stands, is largely shrouded in darkness.
  • However, Ladakh’s recent Union Territory status and government intent to bolster economic opportunities via tourism and the Indian Army expanding lighting to bolster its defence at the India-China border.

 

Striking a balance

• Declared Dark-Reserve: The announcement of Hanle as India’s first Dark Sky Reserve will prevent to a large extent the damage posed by light to the observatory there.
• Astro-tourism: 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.
• Prevent light pollution: Villagers at Hanle will also be given dark curtains to minimise outgoing light from residences.
  • Already, at night time, vehicles are restricted from pointing their beams upwards, and roads will be installed with light delineators.