In search of dark and quiet skies

Last Updated 25 November 2020, 17:21 IST
In search of dark and quiet skies

The night sky has always been a source of inspiration for poets and artists. Many curious minds have studied its role in understanding the secrets of nature and our place in the universe.

The study of celestial objects, which began due to our appreciation of the beauty of the night sky, is unfortunately almost coming to a standstill. One of the main reason being the increasing light pollution.

In order to address the concerns of astronomers, an online workshop by the United Nations Office for Outer Space Affairs and Spain, jointly with the International Astronomical Union (IAU) on "Dark and Quiet Skies for Science and Society", was held earlier this month. The workshop dealt with the effects of artificial lighting at night (ALAN) to the study of astronomical objects. This topic has been attracting the attention of scientists from diverse disciplines.

The workshop brought together the concerns of scientists from many disciplines such as physiology, ecology, geology, space managers etc.

The workshop used results from different research institutes on this problem, and possible mitigation measures were discussed. While artificial lights in the night posed health and environmental issues apart from light pollution, the launch of 1,00,000 satellites in low earth orbits brought the detection of near earth asteroids (NEAs) to a standstill. Radio astronomy also has been affected.

It was felt that interdisciplinary research spanning lighting, medical and environmental research communities is urgently needed. There was a detailed discussion on the effects of artificial light at night on human health. The discussions were based on the alarming statistics on prostrate and breast cancer from all over the world.

Artificial light at night impacts the flora and fauna too. It causes disappearance of moths, and the associated deficit in pollination leads to plant species becoming extinct. The studies related to (de)activation melanin by artificial light which affects the night vision and those that quantified ecological imbalance have also been reported.

The Bio Environment Working Group has reported studies on the impact of new technologies including adaptive lighting, such as light modulation (flicker) and glare. Scrolling display, advertisements and other such wasteful lighting schemes had been pointed out by the International Dark Sky Association. However, whether these recommendations have been implemented by different countries as regulations for outdoor lighting was a key question during our discussions.

The discussions led to an innovative idea — the creation of dark sky oasis (also called a ‘dark sky place’) to protect the night sky. The regulated outdoor lighting policy considered not only the amount of light but wavelengths also. Regulations were specified for sports facilities at night, commercial facilities including open areas of ports by lighting arrangements using flood lighting.

Many professional observatories see measurable impact of light pollution from distances as great as 300 km. Hence, there was a plea for adherence to the minimum required levels and other best practices to reduce urban sky glow.

Radio waves

Radio astronomy, though the youngest entry in to the field has extended our understanding of the universe. It has enabled us to “see” quasars, pulsars, black holes and more recently the gravitational waves.

Observations of radio waves extend to the region of the electromagnetic spectrum frequencies up to 3000 GHz (>100 microns); 21cm lines originating from hydrogen redefined the structure of the Milky Way galaxy and of other galaxies as well. The other 200 and odd molecules like CO (carbon monoxide), HCO, HCN emit at 115.3, 230.5, 345.8, ... GHz are observable only in the radio. The observation demands a radio quiet zone, so that the observatories have to ensure no interference from mobile, airborne or space-borne transmitters (cell phones also are indirectly limited).

However, new technologies using airborne and space-borne use of the radio spectrum, unmanned aerial vehicles (drones), stratospheric high altitude platform stations (HAPS). To this ever growing list is a new addition - the mega-constellations of tens of thousands of satellites in low earth orbit. At any given instant about 10,000 to 50,000 satellites will be hovering above the horizon.

Radio and optical astronomers narrated their struggle in the last six to seven months due to such obstructions to their studies. SpaceX has already launched thousands of satellites and the astronomers reported their systematic findings on the interference. The constellation satellites were deemed to have a reduced reflectivity, which was not the real case. The spoilt images of the interstellar visitor Oumuamua, cluster of galaxies and nebulae bear testimony to this. The measures to annul the effect by appropriate correction for the passage of the satellite were futile even in the radio observations.

Space debris was another matter of serious concern. Albeit an assurance on reusable vehicles, the accumulation of defunct satellites in the near future can pose a threat. The need of the hour is to educate the civic bodies on the ill effect of artificial light on humans and biological systems.

(The writer is with Jawaharlal Nehru Planetarium, Bengaluru)

(Published 25 November 2020, 17:05 IST)

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