Probe ‘touches’ the Sun for the first time
ANASA probe has entered the Sun’s atmosphere and ‘touched’ the blazing corona in a first for solar science. The Parker Solar Probe, which launched in 2018, conducted seven flybys of the Sun before dipping into the corona during its eighth flyby on 28 April 2021. It made three trips into the Sun’s atmosphere, one of which lasted for five hours. In the upper reaches of the solar atmosphere, where temperatures average about 1 million degrees Celsius – hotter than the light-emitting surface of the Sun, which is only 5,500 degrees Celsius – the spacecraft collected atmospheric particles with a special instrument called the Solar Probe Cup. By entering and sampling the Sun’s atmosphere, the Parker Solar Probe accomplished a scientific achievement akin to landing on the Moon.
“Imagine yourself sitting on a beach and staring at the ocean, wondering what lies beneath the surface. This is basically what scientists have been doing for decades, wondering what mysteries lie in the Sun’s corona,” said Nicola Fox, Heliophysics
Division director of the Science Mission Directorate at NASA Headquarters. And just three years after the Parker Solar Probe’s launch, Fox said: “We have finally arrived; humanity has touched the Sun.”
The powerful solar wind, made of streaming plasma and high-energy particles, is born in the corona, but is mostly held back by the Sun’s magnetic fields, which also restrain bursts of plasma that spurt from the Sun’s surface. When the solar wind exceeds a certain speed and extends just past the Sun’s atmosphere, a location known as the Alfvén point, it can break free of these magnetic restraints. However, scientists didn’t know where exactly that point was located.
Now the Parker Solar Probe has answered that question. Prior estimates based on remote images of the corona predicted that the Alfvén point would be found approximately 4.3 million to 8.6 million miles from the solar surface. Parker detected those conditions at a distance of about 8.1 million miles above the Sun, telling researchers that it had entered the Sun’s atmosphere for the first time.
The solar wind and solar flares, swift eruptions of solar radiation, can affect electrical grids and disrupt communication networks on Earth, and the new data from the probe provides an unprecedented glimpse into these solar events. A heat shield protects most of the probe from the Sun, but the Solar Probe Cup had to extend beyond that protection in order to sample the corona. Engineers constructed the cup from materials with very high melting points – sapphire, tungsten, molybdenum and niobium – so that it could function under the extreme heat.
When the cup is exposed and making its measurements, “it’s literally red-hot, with parts of the instrument at more than 1,000 degrees Celsius, and glowing red-orange,” said astrophysicist Anthony Case, the instrument scientist for the Solar Probe Cup. Data collected by the Parker Solar Probe in the corona reveals the Sun as it’s never been seen before, which will help scientists to better understand the roiling forces that generate the enormous quantities of energy powering our Sun and other stars.