15 Million Degrees by Lucie Green
Lucie Green is a Royal Society University Research Fellow based at the Mullard Space Science Laboratory, University College London. Her new book, 15 Million Degrees: A Journey to the Centre of The Sun is an enthralling work that, like all the best non-fiction, will make readers reconsider something they see literally every day. As The Telegraph noted, "The future of solar science is bright, and Lucie Green is an inspiring guide.” Here, Lucie Green discusses what it is like for Tim Peake working in the International Space Station - a man flying close to the sun.
Tim Peake has a bird’s eye view of the Sun from the International Space Station. But does being closer to Sun give him a better perspective?
Tim Peake is a real high-flyer. He lives and works on the International Space Station, 400 km above our heads and always on the move at 28,000 km per hour around the Earth. This means he gets closer to the Sun than the rest of us, but only marginally. Being on the ISS decreases the distance by just 0.0002% of the overall 150 million km between our local star and us, when the orbit takes it across the Earth’s dayside. What’s crucial though isn’t the ability to get ever so slightly closer to the Sun. Instead, it’s being above the Earth’s atmosphere that counts. There, Tim Peake is much more exposed to our Sun’s violent side.
His view is great though. He can look out into space and be guaranteed a clear sky. It also means that, in principle, he can view the Sun in any wavelength he likes should he have the right telescope. This isn’t the case for us on the ground as our atmosphere blocks many of the wavelengths of light that the Sun emits, including its X-rays and much of the UV and radio. That means Tim Peake have a fuller perspective and it’s one that NASA has made use of in the past.
The ISS isn’t the first space station that NASA has worked on. In 1973 a modified Saturn V rocket launched with a third stage that had been altered to provide a home and an orbiting science laboratory for three astronauts at a time. This space station was called Skylab.
Skylab was an orbiting science laboratory that allowed astronauts to conduct medical research, monitor the Earth and carry out astrophysical research, including studying the Sun. This was done with the Apollo Telescope Mount that gathered images of the Sun in visible, ultraviolet and X-ray wavelengths in a compartment about the same size as a transit van. NASA trained the Skylab astronauts in solar physics before they blasted off to work so they were well prepared when they arrived. Once on Skylab they could watch the Sun’s X-ray glow and violent events like solar flares on their TV monitors. They had a view that no one had before or has had since.
The Skylab data led to some important discoveries about the Sun. We learned how magnetic fields in the Sun’s atmosphere structure the electrically charged gas there and the data are still used today.
I made a pilgrimage in 2011 to see Skylab. It fell to Earth on 11th July 1979 due to a lack of funds to keep it functioning and no capability to keep boosting its orbit against the gradual loss of altitude caused by atmospheric drag. Skylab came streaking back to Earth over the Indian Ocean and scattered itself over the southern part of Western Australia. Many bits remained surprisingly intact. Including a large oxygen tank. If you want, you can see these items for yourself. To follow my route, you’ll need to fly to Perth, Australia, and then drive for a couple of days to reach the town of Esperance.
Tim Peake doesn’t have a suite of solar telescopes to use though and he isn’t able to view the X-ray Sun. But he is able to measure other dangerous radiation that the Sun emits. This comes in the form of high-energy electrically charged particles that the Sun blasts out when events like solar flares (explosions) or coronal mass ejections (eruptions) occur. The measurements made on the ISS help us understand more about the science of the Sun and the Solar System, but they also ensure that the astronauts can be kept safe and healthy as we know today that if the Sun sends out too many of these particles it could be extremely harmful for humans on the ISS. These particles can damage cells causing radiation sickness and perhaps cancer so their numbers are monitored. If the numbers rise, space walks are delayed and the astronauts are keep in shielded in the safest parts of the ISS.
Monitoring the space environment for harmful energetic particles is just one approach though. Another is to forecast when these particle showers might occur so that there is time to prepare. In the UK, the Space Weather Operations Centre at the Met Office does this. They are constantly monitoring the Sun, like the Skylab astronauts did, using telescopes in space and on the ground. Watching all the time for the telltale signs that something is brewing. The European Space Agency funds facilities to forecast the weather in space too.
If we can take one thing away from the space-age studies of the Sun it’s that our star is violent and unpredictable. One minute calm, but the next exploding with flashes of X-ray radiation and sending magnetic high-energy particles towards us. And its activity matters to us.
Tim Peake’s view into space is only the half the story though. He can also look down toward the Earth and see another consequence of our active Sun. This takes the form of the stunning aurora – the northern and southern lights. They are a direct consequence of material and magnetic field, expelled from the Sun during a coronal mass ejection, interacting with our own magnetic field and creating a web of electric currents that cause the atmospheric gases to glow. The Sun’s violent side provides Tim Peake with view of nature’s greatest light show. It’s a perspective that’s well worth having.
110 times wider than Earth; 15 million degrees at its core; an atmosphere so huge that Earth is actually within it: come and meet the star of our solar system Light takes eight minutes to reach Earth from the surface of the Sun. But its journey within the Sun takes hundreds of thousands of years. What is going on in there? What are light and heat?