 "Unravelling mysteries of the sun: Where's Nasa's Parker Solar Probe now?")
On November 6, Nasa’s Parker Solar probe came within 234 miles (376 kilometres) of Venus to use the planet’s gravity to slingshot itself closer to the Sun. The gravity-assist maneuvre allowed the probe to throw itself into an orbit closer to the sun to accomplish its mission.
This would not be the first time when the Parker Solar Probe will make close passes of the sun, however, this one would be closest, with the spacecraft coming within 3.8 million miles (6 million km) of the surface of the sun.
Parker is the fastest man-made object
Parker is the fastest object ever designed by humans travelling at a speed of around 435,000 mph (700,000 km/h), at its closest approach. The probe was launched on August 12, 2018 to investigate the mysteries of the corona, the outer atmosphere of the sun.
When Parker makes its close approach, known as perihelion, on December 24 this year, Nasa will be unable to contact it for about three days. Upon being successful, the probe will send a beacon tone to the team on December 27, confirming that it is functioning properly.
"Parker will remain in this orbit for the remainder of its mission, completing two more perihelia at the same distance," the US space agency said.
We know that the visible surface of the sun, the photosphere, has a temperature of around a few thousand kelvins, but the temperature of the corona can reach millions of kelvins.
Aim to investigate Sun’s corona
The corona cannot be heated through heat-transfer processes as it violates the second law of thermodynamics that says, heat always flows spontaneously from hotter to colder regions of matter. Hence, the cooler surface can’t deliver heat to the warmer corona.
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So it has to be another process involving magnetic fields playing a large and dynamic role in corona physics.
However, corona doesn’t take much energy to heat up because of the role helium plays in the calculation.
The 25 per cent mass of the sun is made up of Helium. The helium that carries two electrons loses one of them because of the temperature of the photosphere. This state is known as a partially ionised state. It allows helium to pump out a lot of radiation contributing to the sun’s glow.
But it also keeps the temperature in check as there is an easy ‘escape hatch’ for the sun's heat.
Once things heat up, helium loses its other electron and becomes fully ionised. Then releasing radiation becomes tougher for the sun which means it’s better at trapping heat.
Resultantly, it doesn’t require much energy to heat the corona to ridiculously high temperatures, it could be like 1 kilowatt for every square metre. This means whatever we use, it will be inefficient to heat up the corona and it will still likely do the trick.
That’s where Parker Solar Probe comes into play to study the sun’s region. It has four suites of instruments namely, FIELDS, WISPR, IS-O-IS and SWEAP, to study the corona, the solar wind and the photosphere to compile a complete picture.
Then Parker discovered the strange waves of magnetic-field energy called switchbacks playing a critical role in heating the corona. Switchback starts in the turbulent photosphere where plumes of plasma constantly well up to the surface and slink back down.
When these two magnetic fields bump against each other, the lines disconnect and reconnect forming a giant S-shaped link in the field lines. This kink is called switchback travelling away from the sun and deep into the corona.
In the end, the switchback dissolves, delivering its energy. Astronomers think it is one of the most important (if not the most important) way the sun heats up the corona.