NASAA NASA spacecraft is attempting to make history with the closest-ever approach to the Sun.
The Parker Solar Probe is plunging into our star’s outer atmosphere, enduring brutal temperatures and extreme radiation.
It is out of communication for several days during this burning hot fly-by and scientists will be waiting for a signal, expected at 05:00 GMT on 28 December, to see if it has survived.
The hope is the probe could help us to better understand how the Sun works.
Dr Nicola Fox, head of science at NASA, told BBC News: “For centuries, people have studied the Sun, but you don’t experience the atmosphere of a place until you actually go visit it.
“And so we can’t really experience the atmosphere of our star unless we fly through it.”
NASAParker Solar Probe launched in 2018, heading to the center of our solar system.
It has already swept past the Sun 21 times, getting ever nearer, but the Christmas Eve visit is record-breaking.
At its closest approach, the probe is 3.8 million miles (6.2 million km) from our star’s surface.
This might not sound that close, but NASA’s Nicola Fox puts it into perspective: “We are 93 million miles away from the Sun, so if I put the Sun and the Earth one meter apart, Parker Solar Probe is four centimeters from the Sun – so that’s close.”
The probe will have to endure temperatures of 1,400C and radiation that could frazzle the onboard electronics.
It is protected by an 11.5cm (4.5 inches) thick carbon-composite shield but the spacecraft’s tactic is to get in and out fast.
In fact, it will be moving faster than any human-made object, hurtling at 430,000mph – the equivalent of flying from London to New York in less than 30 seconds.
Parker’s speed comes from the immense gravitational pull it feels as it falls towards the Sun.
PA MediaSo why go to all this effort to “touch” the Sun?
Scientists hope that as the spacecraft passes through our star’s outer atmosphere – its corona – it will solve a long-standing mystery.
“The corona is really, really hot, and we have no idea why,” explains Dr Jenifer Millard, an astronomer at Fifth Star Labs in Wales.
“The surface of the Sun is about 6,000C or so, but the corona, this tenuous outer atmosphere that you can see during solar eclipses, reaches millions of degrees – and that is further away from the Sun. So how is that atmosphere getting hotter?”
The mission should also help scientists to better understand solar wind – the constant stream of charged particles bursting out from the corona.
When these particles interact with the Earth’s magnetic field the sky lights up with dazzling auroras.
But this so-called space weather can cause problems too, knocking out power grids, electronics, and communication systems.
“Understanding the Sun, its activity, space weather, the solar wind, is so important to our everyday lives on Earth,” says Dr Millard.