The biggest sunspot on the face of the sun in more than two decades unleashed a major flare on Friday (Oct. 24), the fourth intense solar storm from the active star in less than a week.

This full-disk image of the sun shows the location of the major X3.1 solar flare (lower right) on Oct. 24, 2014. The solar flare erupted from the largest sunspot on the sun in 24 years.
This full-disk image of the sun shows the location of the major X3.1 solar flare (lower right) on Oct. 24, 2014. The solar flare erupted from the largest sunspot on the sun in 24 years.
Credit: NASA/SDO

The solar flare occurred Friday afternoon, reaching its peak at 5:41 p.m. EDT (2141 GMT), and triggered a strong radio blackout at the time, according to the U.S. Space Weather Prediction Center. NASA's sun-watching Solar Dynamics Observatory captured stunning video of the huge solar flare.

The flare erupted from a giant active sunspot known as AR 12192 and was classified as an X3.1-class solar storm — one of the most powerful types of solar storms on the sun — but it is not the first time the sunspot has made its presence known. [Biggest Solar Flares of 2014 in Photos]

"This is the fourth substantial flare from this active region since Oct. 19," NASA spokesperson Karen Fox wrote in a status update. 

A massive X3.1 solar flare erupts from the giant sunspot AR 12192 on Oct. 24, 2014 in this close-up view from NASA's Solar Dynamics Observatory, a spacecraft that constantly watches Earth's nearest star.
A massive X3.1 solar flare erupts from the giant sunspot AR 12192 on Oct. 24, 2014 in this close-up view from NASA's Solar Dynamics Observatory, a spacecraft that constantly watches Earth's nearest star.
Credit: NASA/SDO

Indeed, on Sunday (Oct. 19), the sunspot fired off a major X1.1-class solar flare, then followed it up with an intense M8.7-class flare on Wednesday (Oct. 22) that was followed that same day by an X1.6 event. 

See how solar flares, sun storms and huge eruptions from the sun work in this SPACE.com infographic. <a href="http://www.space.com/12047-solar-flares-sun-storms-space-weather-infographic.html">View the full solar storm infographic here</a>.
See how solar flares, sun storms and huge eruptions from the sun work in this SPACE.com infographic. View the full solar storm infographic here.
Credit: Karl Tate/SPACE.com

Sunspots are regions of the sun forged by shifting magnetic fields that are cooler than their surrounding solar material, giving them their dark, blemish-like appearance.

Sunspot AR 12192 dwarfs the Earth and is comparable to Jupiter in its size, according to solar astrophysicist C. Alex Young with NASA's Goddard Space Flight Center, who described the sunspot in his blog The Sun Today

The sunspot is the largest of its kind since November 1990, and is larger than a monster sunspot that spawned a series of major solar flares over Halloween in 2003, Young wrote. 

And on Thursday (Oct. 23), the sunspot was hard to miss during a spectacular partial solar eclipse that was visible from North America. Many of the skywatchers who captured photos of the solar eclipse remarked on the surprising sight of a giant sunspot on the face of the sun.

"This was my first time photographing a solar eclipse and I was thrilled to capture the sunspots as well," skywatcher Mark Ezell of Austin, Texas, wrote in an email on Thursday.

X-class solar flares are the most powerful eruptions on the sun. When aimed directly at Earth, X-class flares can potentially pose a danger to astronauts and spacecraft in space, and interfere with navigation, radio and communications signals. M-class flares are ranked as moderate sun storms that can supercharge the Earth's aurora displays. There are also weaker classes of solar storms that have little effect on Earth, including C-class, B-class and even A-class storms. 

"Solar flares are powerful bursts of radiation," Fox wrote in the NASA update. "Harmful radiation from a flare cannot pass through Earth's atmosphere to physically affect humans on the ground, however -- when intense enough -- they can disturb the atmosphere in the layer where GPS and communications signals travel."

Many of us take the sun for granted, giving it little thought until it scorches our skin or gets in our eyes. But our star is a fascinating and complex object, a gigantic fusion reactor that gives us life. How much do you know about the sun?
This image, captured by NASA&apos;s Solar Dynamics Observatory (SDO) on March 10, 2012, shows an active region on the sun, seen as the bright spot to the right. Designated AR 1429, the spot has so far produced three X-class flares and numerous M-class flares.
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Solar Quiz: How Well Do You Know Our Sun?
Many of us take the sun for granted, giving it little thought until it scorches our skin or gets in our eyes. But our star is a fascinating and complex object, a gigantic fusion reactor that gives us life. How much do you know about the sun?
This image, captured by NASA&apos;s Solar Dynamics Observatory (SDO) on March 10, 2012, shows an active region on the sun, seen as the bright spot to the right. Designated AR 1429, the spot has so far produced three X-class flares and numerous M-class flares.
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But X-class solar storms can unleash massive amounts of power.

"An X2 is twice as intense as an X1, an X3 is three times as intense, etc.," Fox wrote.

Despite its sheer power, the X3.1 solar flare on Friday was not the biggest sun storm of the year. On Feb. 24, the sun erupted with a monster X4.9-class solar flare that has topped the solar events of 2014. Smaller X-class flares have occurred occasionally throughout the year. 

Young also wrote that sunspot AR 12192 is the largest sunspot of the sun's current 11-year weather cycle, known as Solar Cycle 24. 

Email Tariq Malik at tmalik@space.com or follow him @tariqjmalik and Google+. Od-Original article on Space.com.