This image might look like an alien star, but it is an image of the Earth’s sun. Captured by the extreme-untraviolet telescope at the Solar and Heliospheric Observatory (SOHO), this colour-coded image highlights the different temperatures of gas in the Sun.

The ESA explains: “An iron atom usually contains 26 electrons. In this image, blue shows iron at a temperature of 1 million degrees celsius, having lost 8 or 9 electrons. Yellow shows iron at 1.5 million degrees (11 lost electrons) and red shows iron at 2.5 million degrees (14 lost electrons). These atoms all exist in the outer part of the Sun’s atmosphere known as the corona. How the corona is heated to millions of degrees remains the subject of scientific debate.

“The constant monitoring of the Sun’s atmosphere with SOHO, and with other Sun-staring spacecraft like the Solar Dynamics Observatory and Proba-2, is allowing solar physicists to build up a detailed picture of the way the corona behaves. This gives them insight into the physical processes that give rise to the corona and its behaviour.”

Image credit: SOHO/ESA, NASA