The Sun has expelled a third intense X-Class solar flare in 24 hours - but Nasa says not to worry.
It is "not physically capable of destroying Earth".
Our sun is currently nearing the period known as 'solar maximum', when activity on its surface rises to an 11 year peak. This solar cycle has been observed regularly since it was discovered in 1843, and indicates a regular fluctuation and not an anomaly.
Above: the third X-class flare in 24 hours
The X3.2 flare which appeared on 13 May is the strongest of 2013 so far, and surpasses the two previous flares which had occurred earlier this week.
The flare was associated with a coronal mass ejection (CME) which left the sun at 1,400 miles per second - so fast it will eventually catch up with the two other X-class flares.
Nasa said it was possible the flare would give a "glancing blow" to its Stereo-B spacecraft, which may be placed into 'safe mode' to withstand the force.
The sunspot which made it is currently facing away from Earth, but will be turning to meet us in the next few days.
But despite the intensity of the flares, Nasa said there was no chance that it would catastrophically harm Earth.
"Some people worry that a gigantic "killer solar flare" could hurl enough energy to destroy Earth," Nasa said on its website. "But this is not actually possible."
"Anyone over the age of 11 has already lived through such a solar maximum with no harm."
However Nasa said that exceptionally powerful flares and CMEs could cause harm on Earth, by interfering with satellites, disrupting power networks and causing issues with GPS networks.
"In an increasingly technological world, where almost everyone relies on cellphones, and GPS controls not just your in-car map system, but also airplane navigation and the extremely accurate clocks that govern financial transactions, space weather is a serious matter."
But the space agency added that while space weather is a problem, it is only in "the same way hurricanes are a problem". Nasa gives warnings to companies that might be affected by serious space weather so they can prepare ahead of time.
Meanwhile the UK government is examining the threat - though concern remains that current plans to proactively prevent damage to vital infrastructure such as the National Grid are not extensive enough to reduce the risk.