NASA launches solar probe to study the Sun
The probe will help to answer many of the most long-standing questions about the Sun, including what drives the solar winds that buffet the Earth.
Launched from Cape Canaveral, Florida, after a last-minute technical problem caused a delay, the Parker Solar Probe is now on its way to the Sun, which it should reach in around three months' time.
It will then spend the next seven years making 24 loops around the Sun to study its atmosphere, using Venus to slingshot it back into orbit. Eventually, it will run out of fuel and turned into the solar wind that it was studying.
Named after Eugene Parker, the first person to describe solar wind, the solar probe is the fastest-moving artificial object in human history. It will travel at a speed of 690,000 kilometres per hour as it whips around the Sun.
Touching the Sun
When it gets to the Sun the probe will pass by the star at a distance of just 6.6 million kilometres. Considering that Mercury orbits the Sun at an average distance of 58 million kilometres, the Parker Solar Probe will get exceptionally close.
The challenges that the spacecraft will face are extreme. Even at such a distance from the Sun the temperature can get as high as two million degrees centigrade. The probe will also have to deal with extraordinary levels of radiation.
The only way it can survive such conditions is thanks to the thin atmosphere of the Sun, known as the corona, which keeps temperatures down.
The Parker Solar Probe is equipped with a heat shield that can withstand 1,400°C. This is still fantastically hot - after all, lava from erupting volcanoes is typically between 700°C and 1,200°C.
The heat shield is an incredible piece of engineering. Even though it is just 10.5 centimetres thick, it will keep the body of the spacecraft at just 30°C. During flybys, if the probe is to tilt out of position even slightly, heat will get behind the shield and the spacecraft will melt.
The electronic wiring has also been specially made for such a mission, considering the heat and radiation experienced. The cables have been suspended inside lab-grown sapphire crystal tubes, while the grids that produce the electronic field have been made from tungsten, which has the highest known melting point of any metal.
Shedding light on the Sun
The probe will help to answer many questions about the star at the centre of our solar system.
One of these relates to what powers the solar wind that flows from the Sun to hit the Earth. Solar wind is made up of charged particles that escape the gravity of the Sun and blow out into space at speeds of more than a million kilometres per hour.
When the conditions are right, this solar wind can cause the auroras at Earth's northern and southern poles - but it can also wreak havoc on satellites and even knock out power grids. There is also immense interest in how this radiation will affect astronauts as they travel through space for long periods of time.
Ken Phillips, a solar physicist and scientific associate at the Museum, says, 'The Parker Solar Probe will actually sample the solar wind - the stream of energetic particles - from close to where the wind is accelerated.
'It will acquire much-needed information about the magnetic fields very near the Sun, which at present are deduced by calculations rather than directly observed. It is also hoped that it will go a long way towards determining the acceleration mechanism, as well as shedding light on the long-term problem of the heating of the solar corona.'
The temperature of the corona is one of the Sun's most enduring mysteries. The surface of the Sun is around 6,000°C. By all accounts as distance from the Sun increases the temperature should get cooler.
But this is not what is seen. Instead, the temperature in the corona begins to climb again. It is hoped that by passing through the Sun's atmosphere, the Parker Solar Probe will help to solve why this might be the case.
Professor Claudio Vita-Finzi, who studies at how changes in the Sun impact the environment on Earth, says, 'What the Parker Solar Probe detects chemically will also tell us the Sun's present external composition and how it has changed over the last 4.5 billion years. This will help us understand how the Sun functions, critical for analysing the contribution of the Sun to climate change over and above the human factor.'
While it will only take three months to get to the Sun, it is expected to be a few years until we start to understand more about the hottest and largest object in the solar system.