The sun may be doing humanity an unexpected favour. New research shows that heightened solar activity helps push space debris out of Earth's orbit more quickly, a finding that could help space agencies plan safer missions. Scientists at India's Vikram Sarabhai Space Centre tracked 17 pieces of orbital rubbish over 34 years. They found that once sunspot numbers climbed to roughly 70 per cent of their cycle peak, debris began losing altitude at a noticeably faster rate. This is the first study to confirm what researchers had long suspected: solar activity and the fate of space junk are directly linked.
Why the Sun's Heat Matters Up There
The sun runs on an approximately 11-year cycle. At its most active, sunspots multiply and intense radiation floods outward, heating a high layer of Earth's atmosphere called the thermosphere. This causes it to expand upwards. Satellites and debris orbiting between 160 and 2,000 kilometres above Earth suddenly encounter thicker air, which creates drag, slows them down, and pulls them into a lower orbit, eventually sending them tumbling back towards Earth.
"Here we show that space debris around Earth loses altitude much faster when the sun is more active," said Ayisha M Ashruf, a scientist and engineer at the Space Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram, India, and the corresponding author of a new study in Frontiers in Astronomy and Space Sciences.
"For the first time, we find that once solar activity passes a certain level, this loss of altitude happens noticeably more quickly. This observation is expected to be key for planning sustainable space operations in the future."
A Useful Pattern for Space Planning
The 17 tracked objects, circling Earth every 90 to 120 minutes, dropped several kilometres in altitude each time solar activity crossed that sunspot threshold. This reliable pattern, observed across three consecutive solar cycles from 1986 to 2024, could prove enormously useful. As space debris continues to accumulate, knowing when the sun will naturally clear some of it away could help mission planners choose smarter, safer launch windows.
