The sun makes life on Earth possible but, despite this life-sustaining role, scientists know surprisingly little about our nearest star. The €1.35 billion Solar Orbiter – a joint European Space Agency and Nasa mission – is due to launch from Cape Canaveral shortly, with a very significant Irish input, and plans to change all that.
One mystery Orbiter scientists will seek to answer is why the surface temperature of the sun is 5,500 degrees, while the temperature of its enveloping corona – the layer of blistering, hot plasma gas that begins about 2,000km off the solar surface and extends for millions of kilometres into space – is thought to be 2 million degrees.
That’s not the only question that scientists will be seeking answers to. There is also the question of how the solar wind from the sun is produced. This wind is a stream of electrically-charged particles spat out from the upper atmosphere of the sun. The particles hurtle across space, and slam into Earth’s atmosphere causing a number of notable effects, including the northern and southern lights.
Prof Peter Gallagher, head of astrophysics at the Dublin Institute for Advanced Studies, is co-investigator on the Solar Telescope Imaging X-Rays (Stix) instrument. This is one of six scientific instruments which will observe the sun and send imagery to Earth. Four other instruments will measure the solar wind including electrical and magnetic fields associated with it.
“It will fly past Venus, fly past Mercury and go into the inner solar system,” says Gallagher, who formerly worked at Nasa and Trinity College Dublin.
“It will have cameras that are going to take photographs or images of the sun and also it will have these in-situ detectors that will basically ‘taste’ the solar wind as it goes past.
“It will tell us about the nature of the solar wind, it will tell us where the solar wind comes from. It will help us understand these explosions called solar flares and solar storms on the surface of the sun. It will be the highest resolution pictures we have ever had of the surface of the sun.”