NASA’s Parker Solar Probe will set the controls for the heart of the Sun

NASA is today revealing more about a daring mission to send a spacecraft flying closer to the Sun than ever before. And they gave it a new name – the Parker Solar Probe.

Solar Probe Plus
An artist’s impression of the Parker Solar Probe spacecraft approaching the Sun, with its shield pointing sunwards to protect the experiments on board. Image credit: Johns Hopkins University Applied Physics Laboratory

The explorer, previously known as Solar Probe Plus, will swoop in to a distance of just 6 million km (3.8 million miles) where temperatures soar to nearly 1,400° Celsius. There it will sample and study the Sun’s atmosphere, known as the corona, to learn more about how it is produced and its effect on Earth and space weather.

The Parker Solar Probe’s new name honours astrophysicist Professor Eugene Parker who first proposed the existence of the flow of material from the Sun that we now know as the solar wind.

The robotic spacecraft, due to launch in a window stretching from July to August, 2018, will fly on an elongated, elliptical orbit that, over seven years, brings it closer and closer to the Sun, which is the only star we are able to examine close-up.

It will zoom past Venus seven times during that time, manoeuvres that will gradually reduce its orbit. Eventually, the Parker Solar Probe will get to a distance of about nine times the visible diameter of the Sun. That is an eighth of the closest distance that innermost planet Mercury manages from the Sun, which is 46 million km (28.5 million miles).

The Sun – powerhouse of the Solar System

Just like a comet, or any other object on an extended orbit, the spacecraft’s speed will vary according to Kepler’s laws of planetary motion. When nearest the Sun, it will be speeding at an astonishing 725,000 km per hour (125 miles per second). That is fast enough to fly once around the Earth’s equator in 3.3 seconds!

Despite flying into a cosmic furnace, the probe will be able to shield its scientific instruments against the 1,400° C heat, keeping them close to normal room temperature.

Solar Probe Plus's orbit
This diagram illustrates the Parker Solar Probe’s reducing orbit compared to those of the Earth, Venus and Mercury. Image credit: Johns Hopkins University Applied Physics Laboratory

Scientists know that we already exist in the tenuous outer region of the corona because it reveals itself as the solar wind which impacts our magnetic field and causes the spectacular aurora.

But apart from natural light shows, the Sun can also produce blasts of radiation from solar storms that could be devastating for Earth in the modern technological age, hurling millions of tons of material out into space at speeds of many millions of kilometres an hour.

A solar flare, or an eruption called a coronal mass ejection (CME) in our direction could destroy power grids and communication networks on the ground and fry electronic circuits on spacecraft.

It is estimated that a solar event on the scale of one called the Carrington Event that was witnessed in the 19th Century would today cause two trillion dollars worth of damage in the US alone.

The Parker Solar Probe aims to help avoid such disasters but greatly boosting our knowledge of the Sun, following a number of similar missions that have sent spacecraft to monitor the Sun’s behaviour from a safer distance. It will seek to answer questions such as why the solar corona is very much hotter than the Sun’s visible surface, how it is driven by magnetic fields, and what accelerates the solar wind across the Solar System.

Parker Solar Probe
The mission patch for the newly renamed Parker Solar probe. Image credit: NASA/APL

ESA is working on its own latest mission to study the Sun, ESA Solar Orbiter, which is now also due to launch in 2018.

Other probes to have studied the Sun include NASA’s STEREO pair of spacecraft, and Soho, which has had medical scanning techniques applied to map the corona in 3D.

Parker Solar Probe’s instruments

The Parker Solar Probe will carry four bits of kit to study and photograph the Sun.

The Fields Experiment (FIELDS) will make direct measurements of the Sun’s electric and magnetic fields, and sniff and taste the plasma and radiation around the spacecraft. It is led by Professor Stuart Bale of the University of California, Berkeley.

The Integrated Science Investigation of the Sun experiment (IS☉IS) will observe energetic particles leaving the Sun, including electrons, protons and heavy ions that are accelerated to high energies in the solar corona. Leading the investigation is Dr David McComas, of Princeton University.

The Wide-field Imager for Solar PRobe (WISPR) will use telescopes to take photos of the solar corona and inner heliosphere region of the Sun’s atmosphere. This will help map the structure of the solar wind and turbulence within it. Dr Russell Howard, of the US Naval Research Laboratory, will lead this part of the mission.

Finally, the Solar Wind Electrons Alphas and Protons (SWEAP) investigation will count the most abundant particles in the solar wind – electrons, protons and helium ions – and measure how fast they travel, their density and temperature. Professor Justin Kasper, of the University of Michigan/ Smithsonian Astrophysics Observatory, leads this area of study.

By Paul Sutherland

Paul Sutherland has been a professional journalist for nearly 40 years. He writes regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy, plus he has authored three books on astronomy and contributed to others.

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