When Suhani Gupta and her sister spot more than seven stars from their balcony in Gurugram, they have a reason to celebrate. They step outside, open Stellarium, an astronomy app, and try to identify the constellations above them.

In a city where the night sky rarely offers a clear view of the stars, even a handful can turn an ordinary evening into an occasion.

“My sister and I get excited when we see more than seven stars in the sky,” Suhani tells The Better India.

The sisters initially assumed that air pollution was responsible for the limited visibility. After all, Gurugram frequently experiences haze. But visits to her grandparents in Udhampur, Jammu and Kashmir, offered Suhani a different perspective. The sky there appeared far more generous with stars.

The stars had not suddenly multiplied in the mountains. Something about the surroundings had changed.

That difference led Suhani to investigate light pollution — the excessive or poorly directed use of artificial light that brightens the night sky and makes celestial objects harder to see. Buildings, roads, commercial establishments and other sources of outdoor lighting can contribute to this glow.

The consequences extend beyond astronomy, affecting nocturnal wildlife, ecosystems and human exposure to darkness.

But how could a school student measure a problem that even many adults rarely recognise?

In May 2025, Suhani, now a Class 12 student, began teaching herself image processing and developing SkyQi, a free online platform that estimates night-sky quality using photographs taken on smartphones.

The project has since grown into a citizen-science initiative, attracting observations from users across dozens of countries.

In 2026, she took the investigation further. Using NASA satellite data, she examined changes in night-time radiance across 50 Indian cities between 2015 and 2025. Her analysis found that the median city's measured night-time radiance was 70% higher in 2025 than in 2015, while 47 of the 50 cities recorded an increase. Leh, known for its dark skies and astronomy tourism, showed the steepest rise in her dataset, at 546%.

The findings do not directly measure how bright the sky appears to someone standing on the ground. They do, however, raise questions about how urban growth, tourism and outdoor lighting are changing India's nights.

For Suhani, the aim is to make those changes easier to observe, understand and eventually address.

From a school astronomy club to a pollution problem

Suhani's interest in light pollution began in 2024, when she was part of her school's space society. During meteor showers and other astronomical events, members would gather on voice chat at around 3 am to watch the sky.

Observing the stars required patience. Participants would spend about 30 minutes outside, allowing their eyes to adjust to the darkness before attempting to identify celestial objects.

“While we generally do that to adjust to the moon’s brightness, the haze in our sky was much more, and that is kind of how I got into light pollution,” she explains.

She began watching YouTube videos and reading research on the effects of artificial light on human health, wildlife,........

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