Two huge solar flares hit the Earth this week, resulting in dramatic auroras that could be seen across the northern sky.
Nasa say that two "coronal mass ejections" - the casting off by the Sun of matter and radiation in the form of a solar wind - were recorded on 16 June.
The flares originated from the AR 1504 region of the sun, which has recently become active and started producing flares.
The first flare lasted for about three hours and travelled to Earth at about 375 miles per second, according to Nasa, and were detected by the Advanced Composition Explorer (ACE) at about 4.55am EDT. The second arrived much faster, and may have also hit Mars.
The auroras, made when the solar wind hits the Earth's magnetic field, were seen as far south as Iowa, Nebraska and Maryland.
A solar flare is an intense burst of radiation coming from the release of magnetic energy associated with sunspots. Flares are our solar system's largest explosive events.
They are seen as bright areas on the sun and they can last from minutes to hours. We typically see a solar flare by the photons (or light) it releases, at most every wavelength of the spectrum.
The primary ways we monitor flares are in x-rays and optical light. Flares are also sites where particles (electrons, protons, and heavier particles) are accelerated.