Light Pollution & Dark-Sky Reserve


    In News

    • Recently, the district administration of Ladakh designated six hamlets within the Changthang Wildlife Sanctuary as a dark-sky reserve.

    New Study

    • Title: 
      • Citizen scientists report global rapid reductions in the visibility of stars from 2011 to 2022
    • What they Found: 
      • Researchers from Germany and the U.S. analysed a global database of what the dimmest star visible from a particular location is.
      • They found that non-natural light had increased the brightness of the artificial glow of the night sky, or skyglow, by 9.2-10% every year between 2011 and 2022. 
      • The skyglow had brightened around:
        • 6.5% over Europe, 
        • 10.4% over North America, and 
        • 7.7% over the rest of the world.
    • Disagreement with satellite data: 
      • Satellite-based data has indicated that the rate of increase has been around 2% per year. 
    • Reason of discrepancy:
      • The discrepancy is probably because satellites are unable to ‘sense’ blue light emitted by LEDs and to study light that is emitted parallel to the ground.
      • Visible light emitted by many sources is divergent, so light emitted insufficiently downward could find its way into the sky. 
      • Almost all surfaces in cities reflect light, meaning a portion of entirely down-cast light will be reflected upwards, contributing to night-time light pollution. 
    • Global Status:
      • Africa:
        • It had just 452 observations between January 2011 and August 2022 in the database. 
      • China & Brazil:
        • There were no entries from China or Brazil — both rapidly industrialising nations — in the study. 
    • India: 
      • A small Observation was made at the Indian Astronomical Observatory (IAO) before and after the power cut in Hanle, the number of stars that become invisible when the monastery is lit is striking. 
      • 19.5% of India’s population — the lowest fraction among G20 countries — experiences a level of skyglow that would at least keep the Milky Way galaxy out of sight and at most render “dark adaptation for human eyes” impossible. 
      • Between 2012 and 2016, India’s lit area increased by 1.07-1.09%.
      • The average radiance of “stably lit areas” — for example, excluding wildfires — increased by 1.05-1.07%.


    Dark-Sky Reserve

    • About: 
      • It is an area whose sky is free of light pollution
      • 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. 
      • The authorities safeguard telescopes’ access to dark skies by actively lowering light pollution around their sites.
      • Several such reserves exist around the world but none so far in India.
    • Origin: 
      • When private space venture company SpaceX’s Starlink constellation of small satellites began covering the view of ground-based telescopes around the Earth, the idea of the sky as a natural resource capable of being polluted became popular. 
      • These incidents highlighted the absence of a global treaty to reduce light pollution more noticeable. 
    • Nomination by: 
      • The International Dark Sky Association is a U.S.-based non-profit that designates places as International Dark Sky Places, Parks, Sanctuaries and Reserves, depending on the criteria they meet. 
    • Significance:
    • The reserve will boost astro tourism in India and will be one of the world’s highest-located sites for optical, infrared, and gamma-ray telescopes.
    • The astronomical observatories located in the area particularly to keep the skies dark.



    • Health impact: 
      • It stimulates the cone cells in human eyes, which is possible only when an environment is considered to be well-lit.
      • By disrupting the circadian rhythm, artificial light at night can hamper the production of melatonin, an influential hormone in the human body which affects sleep, moods and cognition.
      • Circadian disruption increased the risk of breast cancer among night-shift workers by 40%. 
    • Affects Flora and fauna: 
      • Artificial light at night affects both people and wildlife in significant ways. Lit beaches deter sea turtles from coming ashore to nest. 
      • Skyglow keeps trees from sensing seasonal variations. 
      • Young burrow-nesting seabirds don’t take flight unless the nesting site becomes dark. 
      • Clownfish eggs don’t hatch when exposed to artificial light at night, killing the offspring.
      • It interferes with multiple aspects of insect life and allows insect predators to hunt for longer.
    • Use of LEDs:
      • Regardless of historical or geographical context, humans tend to use as much artificial light as they can buy for about 0.7 percent of GDP. 
      • Even though LEDs have become more efficient, their utilisation hasn’t decreased, which in turn means the carbon emissions due to their production and use hasn’t decreased.


    Way Ahead

    • Villagers and residents also need to be trained to help visitors with astronomical observations.
    • There should be restrictions during the evening and night to vehicles and headlights. 

    Indian Astronomical Observatory – Changthang Wildlife Sanctuary

    • The Indian Astronomical Observatory, the high-altitude station of IIA, is situated to the north of Western Himalayas, at an altitude of 4,500 metres above mean sea level. 
    • Located atop Mt. Saraswati in the Nilamkhul Plain in the Hanle Valley of Changthang, it is a dry, cold desert with sparse human population and has the Hanle monastery as its nearest neighbour. 
    • The cloudless skies and low atmospheric water vapour make it one of the best sites in the world for optical, infrared, sub-millimetre, and millimetre wavelengths.


    • It is about 4,500 metres above sea level and it hosts telescopes .
    • It is regarded as one of the world’s most optimal sites for astronomical observations. 
    • The Himalayan Chandra Telescope (HCT), High Energy Gamma Ray telescope (HAGAR), the Major Atmospheric Cherenkov Experiment Telescope (MACE) and GROWTH-India are prominent telescopes located at the Hanle observatory.

    Source: TH