Solar Activity Speeds Up Space Junk Return

As solar activity increases during its peak cycle, space debris orbiting Earth is falling back to the planet more quickly, according to new research. When sunspots on the Sun’s surface reach high numbers, objects in low Earth orbit lose altitude faster than usual.

A study published in Frontiers in Astronomy and Space Sciences found that when sunspot numbers reached about 70% of their peak levels, space debris experienced a sharp increase in orbital decay. This means they drop toward Earth more rapidly due to added atmospheric drag caused by solar heating.

The Sun’s radiation fluctuates over an 11-year cycle. At its peak, increased solar activity heats and expands the thermosphere—a layer of atmosphere above Earth. When this happens, space debris in low Earth orbit (which spans about 160 to 2,000 kilometers above Earth) encounters more atmospheric resistance. This added friction slows down the debris, causing it to fall back to Earth sooner.

Researchers tracked 17 pieces of space junk for over three decades and observed how their orbits changed during three solar cycles. Each time solar activity peaked, the debris experienced a noticeable drop in altitude before stabilizing until the next cycle began.

This finding is important for managing space operations as humanity faces growing challenges from orbital debris colliding with satellites and spacecraft. Understanding how solar activity affects space junk could help improve predictions and planning for future missions.