Nature’s giant vacuum cleaner: Scientists reveal how the Sun is secretly cleaning Earth’s space junk

As Earth’s orbit becomes increasingly crowded with decommissioned satellites and fragments from the 1960s, however, researchers have identified a natural mechanism for orbital clearance. Research published in Frontiers in Astronomy and Space Sciences reveals that when solar activity increases, it acts like an ‘orbital broom,’ accelerating the re-entry of orbital debris. According to the study published on Frontiers, by examining 36 years of data, scientists at the Vikram Sarabhai Space Centre pinpointed a crucial level of solar activity, around 67 per cent of the solar cycle's peak, where debris quickly descends into Earth's atmosphere. This finding offers a key tool for space agencies to predict and manage orbital traffic, helping future satellite missions last longer.The main reason for this ‘cleanup’ is the expansion of Earth's thermosphere. When solar activity is high, the Sun emits intense ultraviolet radiation and charged particles. This energy heats the upper atmosphere, causing it to expand outward. As a result, the atmosphere stretches further into space, increasing friction on objects in low-Earth orbit (LEO) as noted in a study published on Frontiers. This drag slows these objects down. Eventually, they lose altitude and burn up when re-entering the atmosphere. Research, led by Ayisha M Ashruf and her team, conducted groundbreaking research on the orbital life of 17 objects sent into space from 1962 to 1989, as noted on Frontiers. They discovered something fascinating: orbital decay doesn't occur at a constant rate. Instead, it speeds up significantly when solar activity hits a certain point. Specifically, when solar flux reaches about 67 per cent of its maximum during a cycle, space junk undergoes accelerated descent. This ‘tipping point’ helps scientists pinpoint the exact start of the solar cycle's cleansing phase. Recognising when these solar-driven cleanup events occur is crucial for modern space technology like the Starlink or OneWeb mega-constellations. The atmosphere expands, causing active satellites to encounter more drag. This forces them to consume additional fuel just to stay in their designated positions. Thanks to the 67 per cent threshold discovery, mission controllers can now more accurately plan fuel usage and improve collision avoidance strategies, especially since debris density shifts quickly during the solar maximum.A remarkable dataset was used in the study, following objects launched from the early days of space exploration. Observing these over three solar cycles, each about 11 years long, gave insights into the effects of long-term solar variability on defunct spacecraft. The Vikram Sarabhai Space Centre (VSSC) delivered the most detailed analysis yet. Their findings highlighted how the Sun acts as a crucial natural barrier against the Kessler Syndrome, a hypothetical situation where space debris becomes so abundant that it leads to a destructive chain of collisions.