Solar activity could become the great cleaner of space debris. A recent study reveals that pieces of orbital junk fall faster toward Earth when the sun is agitated, especially beyond a certain threshold.
In low Earth orbit, the residual atmosphere slows objects down. But when the sun is active, it heats and expands this gaseous envelope, increasing drag. The debris then slows further and its descent accelerates. Until now, it was unknown whether there was a threshold of solar activity beyond which this phenomenon becomes significantly more pronounced.
To find out, researchers tracked the trajectory of 17 debris pieces launched in the 1960s for 36 years. This period covers three complete solar cycles, each lasting about 11 years. The team cross-referenced this data with solar activity records from the German Research Centre for Geosciences.
The scientists thus established a direct relationship: when the sun is more active, the atmospheric density around the debris increases. This creates additional resistance that slows their orbit and hastens their fall. "For the first time, we observe that beyond a certain level of solar activity, this loss of altitude occurs significantly faster," explains Ayisha Ashruf, lead author of the study.
This discovery has important implications for satellites. During solar activity peaks, active spacecraft also experience increased drag and require more orbital corrections. "This directly affects their lifespan and the amount of fuel needed, especially for missions launched near a solar maximum," Ashruf notes.
With nearly 130 million fragments of debris in orbit, better understanding their behavior is also important for avoiding collisions. This study is published in the journal
Frontiers in Astronomy and Space Sciences.