NASA has spotted an X-class solar flare (the most powerful solar flares) on the surface of the sun - the first such flare since 2017.
The flare produced a pulse of X-rays which hit Earth’s atmosphere and blacked out shortwave radio signals over the Atlantic.
The X-Class flare is a sign that the sun is beginning a new cycle of activity - Solar Cycle 25 - which is set to peak in July 2025.
Other signs that the solar cycle is becoming more active include recent coronal loops of plasma spotted on telescopes.
NASA said: "Solar flares are powerful bursts of radiation. 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.’
X-class flares are the most powerful solar flares: the one this week was ranked X1.5 – X-class denotes the most intense flares, while the number provides more information about its strength.
An X2 is twice as intense as an X1, an X3 is three times as intense, etc.
The most powerful on record was an X28 in November 2003.
NASA’s orbiting Solar Dynamics Observatory spotted the flare over the weekend.
The Solar Dynamics Observatory blog wrote: "At 1430 UTC on July 3, 2021, the first X-class flare (actually an X1.5 flare) of Solar Cycle 25 was seen on the Sun.
"There were also several B and C flares, and even one M flare in the day before the X1.5 flare.
"There was no active region associated with the X1.5 flare. A large region of magnetic field that was rotating off the disk is probably the home of the flares.
"Solar Cycle 25 is starting to get more interesting!"
The Solar Cycle 25 Prediction Panel, an international group of experts co-sponsored by NASA and NOAA, announced that solar minimum occurred in December 2019, marking the start of a new solar cycle.
Scientists use sunspots to track solar cycle progress.
The dark blotches on the Sun are associated with solar activity, often as the origins for giant explosions (such as solar flares or coronal mass ejections) which can spew light, energy, and solar material into space.
Lika Guhathakurta, solar scientist at the Heliophysics Division at NASA Headquarters in Washington said in December, ‘As we emerge from solar minimum and approach Cycle 25’s maximum, it is important to remember solar activity never stops; it changes form as the pendulum swings.’
Solar Cycle 25 is anticipated to be as strong as the last solar cycle, which was a below-average cycle, but not without risk.
Watch: Man captures footage of solar flare from back yard