A once-in-century solar storm could fry power grids and knock out satellites. Here's why scientists worry it could happen soon.

• Most solar storms are pretty harmless, but every so often, the sun can send hugely powerful storms.
• These are strong enough to cause widespread power blackouts and bring down satellites. 
• We are more likely than usual to be hit by a super-strong storm in the coming years, scientists say

The sun is always fizzing and popping and this constantly sends solar energy toward the Earth. But sometimes it's more serious.

On an average day, its vast solar energy is deflected without causing much damage. But every so often, the sun sends a storm so powerful it can tear open the Earth's magnetic fields.