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.

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Above: the third X-class flare in 24 hours


But the appearance of three powerful flares in less than 24 hours has still surprised many - and now the sun spot which produced them is turning towards the Earth.

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."

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  • MYTH: Solar flares have no effect on Earth.

    REALITY: Solar flares can release electromagnetic radiation that's strong enough to disrupt electric power grids, satellites, GPS, and radio communications. Pictured: Coronal mass ejection as viewed by the Solar Dynamics Observatory on June 7, 2011.

  • MYTH: A solar flare could kill us all.

    REALITY: Only a tiny fraction of the energy liberated by a solar flare reaches the Earth, because we're protected by our planet's atmosphere. "We have a very long record that shows that even the strongest flares can't blow out the atmosphere," Antti Pulkkinen, a research scientist at NASA's Goddard Space Flight Center, told CNN. Pictured: A solar eruptive prominence as seen in extreme UV light on March 30, 2010 with Earth superimposed for a sense of scale.

  • MYTH: Solar flares occur at random.

    REALITY: Solar flares follow an 11-year cycle. Pictured: Full-disk images of the sun's lower corona during solar cycle 23, as it progressed from solar minimum to maximum conditions and back to minimum (upper right).

  • MYTH: 'Aftershocks' are rare.

    REALITY: About one in seven flares is followed by an aftershock -- the flare springs back to life, producing an extra surge of ultraviolet radiation. Pictured: Sunspot 1112, crackling with solar flares, spotted by NASA's Solar Dynamics Observatory on October 16, 2010.

  • MYTH: Solar flares can be seen with the naked eye.

    REALITY: To see a solar flare from Earth, you must use a solar telescope. Never stare directly at the sun. What you can see with a naked eye are northern lights, which can be triggered by solar eruptions. Pictured: Northern lights (aurora borealis) over Lake Elora in Minnesota on July 15, 2012.

  • MYTH: Solar flares were discovered only recently.

    REALITY: Solar flares were first observed in 1859 by English astronomer Richard Carrington. Pictured: Sunspots of September 1, 1859 as sketched by Richard Carrington.

  • MYTH: Solar flares are small compared to other explosions in our solar system.

    REALITY: Solar flares are among the biggest explosions in our solar system. "They erupt near sunspots with the force of a hundred million hydrogen bombs," Robert Lin of UC Berkeley's Space Science Lab said in <a href="http://cse.ssl.berkeley.edu/energy/Resources/Living%20With%20a%20Star/------START%20HERE-------/6/solar_f.htm#top">a written statement</a>. Pictured: Solar and Heliospheric Observatory (SOHO) spacecraft image of a solar flare on October 28, 2003.

  • MYTH: Solar flares can knock satellites from orbit.

    REALITY: When satellites do fall out of orbit, it's because Earth's gravity is pulling them down. Pictured: Solar Dynamics Observatory (SDO) image of an M7.9 class solar flare on March 13, 2012.

  • MYTH: Solar flares produce sunspots.

    REALITY: It's actually the other way around. Magnetic fields associated with sunspots -- cool, dark regions of the sun's surface -- can sometimes give rise to solar flares. Pictured: NASA's sun-observing TRACE spacecraft image shows a large sunspot group from September 2000.

  • MYTH: Solar flares and solar prominences are different names for the same phenomenon.

    REALITY: Solar flares and prominences are different. A prominence is a loop of plasma traveling along magnetic field lines. Sometimes this loop collapses back into the sun -- or, if the prominence erupts, a solar flare can result. Pictured: A solar prominence on October 19, 2012, captured by NASA's Solar Dynamics Observatory (SDO).

  • MYTH: Solar flares and coronal mass ejections are the same thing.

    REALITY: Coronal mass ejections are also explosions on the sun--but a different type of explosion. "If a solar flare is a tornado, very intense, very focused, very local, a coronal mass ejection is a hurricane," astronomer Phil Plait told The Huffington Post. Pictured: An X1.4 solar flare associated with a coronal mass ejection on July 12, 2012.


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.