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TheSunis wakingup

eing in ultraviolet, at a wavelength of 304 angstroms, this picture is presented in false colour, a
ery orange that seems appropriate for a roiling Sun. At this wavelength NASA’s Solar
Dynamics Observatory, which took the image on 3 December 2020, sees dense plumes of plasma at
50,000 degrees Celsius – slightly cooler than their surroundings – hanging in the chromosphere,
above the photosphere. e plumes are familiar to us as laments and prominences, which we see
here as wispy tendrils on the limb of the Sun, or as the bright areas on the Sun’s face.

Four days before this image was taken, on 29 November, the Sun unleashed its most powerful are
in three years, a medium-sized (class M4.4) outburst that instigated a coronal mass ejection (CME)
that buffeted Earth’s magnetosphere. Fortunately, in this case, our planet was able to ward off the
worst of the CME’s effects. Image: NASA/SDO.

This extreme ultraviolet image of the Sun captures our nearest star in an increasingly active

state. Now that we have officially entered solar cycle 25, the Sun is gradually awakening from

its slumber.

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The Sun is waking up

January 2021

Astronomy Now