Secrets of the Sun Told by Parker

James Maynard
Dec 12, 2019 · 6 min read

The Parker Solar Probe — the first spacecraft to ever “touch” the Sun, is revealing deep, hot secrets about the physics of our local star.

Launched August 12, 2018, the Parker Solar Probe is the first spacecraft ever designed to skim the surface of the Sun, in an quest to understand the physics underlying some of the most mysterious activities of our parent star. Since it’s launch, the robotic explorer has collected gigabytes of data about the Sun and the atmosphere surrounding it.

Solar storms can endanger satellites and electronics on Earth, and by better understanding these outbursts, we may find means by which we can predict these events, and protect modern civilization from their effects. Astronomers also want to know more about the solar wind — a constant outflow of material from the Sun.

A coronal mass ejection which erupted from the Sun on August 31, 2012. Fortunately, it wasn’t headed our way. Image credit: NASA Goddard Space Flight Center

The solar wind races from the Sun at around a million miles an hour, affecting the magnetic field of the star, driving space weather throughout the Solar System.

Coming in for a Closer Look

Spacecraft have recorded regions of dense stellar material on the surface of the Sun, and they are thought to heat and accelerate particles, which race across the solar system. Carrying away some of the magnetic charge of the Sun, these outbursts easily dwarf the size and energy of the Earth’s magnetic field. In any collision with our home planet, the protective magnetic field around our world would be easily overwhelmed.

“When structures in the solar wind reach Earth, they can drive dynamics in Earth’s magnetosphere, including particle precipitation from Earth’s radiation belts,” said Nicholeen Viall, from NASA’s Goddard Space Flight Center.

Since entering orbit around the Sun. the Parker Solar Probe has utilized cameras to study the behavior of our local star, as well as the characteristics of solar wind structures passing the spacecraft.

Astronomers on Earth took these readings, and combined this information with data collected by the STEREO-A spacecraft and satellites in order to piece together the physics behind these solar phenomenon. The STEREO-A observatory is in orbit around the Sun at a near 90-degree angle from the Earth. This positioning allowed scientists to view the regions of the corona as Parker flew through them, providing a better view of magnetic disturbances caused by the solar wind.

“We think of the solar wind — as we see it near Earth — as very smooth, but Parker saw surprisingly slow wind, full of little bursts and jets of plasma,” said Tim Horbury of the Imperial College London, and lead researcher on Parker Solar Probe’s FIELDS instruments.

Horbury used data from this suite of instruments to examine switchbacks — events where the solar magnetic field bends back on itself, a phenomenon first revealed by Parker, and announced in December 2019.

Five new discoveries already made by the Parker Solar Probe. Video credit: NASA Goddard

Oddly, the atmosphere of the Sun is hotter than its surface — almost as if the air felt warmer far from a campfire than near the flames. This counter-intuitive phenomenon is one of the large mysteries that NASA hopes to answer with the Parker mission.

“We think the switchbacks are probably related to individual energetic energy releases on the Sun — what we call jets. If these are jets, there must a very large population of small events happening on the Sun, so they would contribute a large fraction of the total energy of the solar wind,” Horbury describes.

That was a Lucky Shot, Sun!

Even denser and faster than the solar wind, coronal mass ejections (CME’s) can cause significant problems with satellites and electronics on Earth. These events are incredibly difficult to predict, and often cannot be seen by Earth-bound observers or the STEREO-A observatory. Even when they are spotted in time, it is a challenge to predict which may pose a hazard to Earth.

“O thou Sun, send me as far over the earth as is my pleasure and thine, and may I make the acquaintance of good men, but never hear anything of bad ones, nor they of me.” — Apollonius of Tyana

The best chance astrophysicists have to understand a particular CME burst is by studying the region of the Sun from which it erupted. Under the best of conditions, this can be challenging, but a special class of these events called stealth CME’s, provides little evidence of their origins.

However, in November 2018, the Parker Solar Probe was impacted by one of these stealth CME’s, allowing researchers a unique opportunity to study these events up close for the first time.

“Flying close to the Sun, Parker Solar Probe has a unique chance to see young CMEs that haven’t been processed from traveling tens of millions of miles. This was the first time we were able to stick our instruments inside one of these coronal mass ejections that close to the Sun,” said Kelly Korreck of the Smithsonian Astrophysical Observatory.

Study of this stealth CME could allow astronomers to better understand these events, and trace this particular outburst to the region of the Sun from which it erupted.

Well, Time to Hit the Dusty Trail…

In addition to studying the atmosphere of the solar corona and ejections of materials from the Sun, the Parker Solar probe also revealed new information about the Geminid meteor shower (peaking this year between December 13 and 14).

Most annual meteor showers are the result of the Earth passing through the debris field left behind by passing comets and asteroids as they break apart in space.

The object at the heart of the Geminid shower is the asteroid Phaethon, and the Parker Solar Probe observed a trail of debris — 96,000 kilometers (60,000 miles) long- streaming out from the body. It is this ribbon of material thorough which the Earth passes, resulting in the annual display of shooting stars. Dim and orbiting close to the Sun, this marks the first time this trail has been seen by astronomers.

A trail of rocks and dust seen orbiting the Sun.
A trail of rocks and dust seen orbiting the Sun.
A trail of debris from the asteroid Phaethon, seen by the Parker Solar Probe. Image crBrendan Gallagher/Karl Battams/NRL

Astronomers believe the trail of dust and pebbles left behind in the wake of Phaethon contains a total mass of around one billion tons, a lower value than previously estimated.

Since its launch, the Parker Solar Probe has completed three trips around the Sun. Over the course of its entire mission, the spacecraft is expected to complete 21 trips around our parent star — with each pass coming closer than the one before to the fiery sphere. During it’s next close approach to the Sun, Parker will be just 18.6 million kilometers (11.6 million miles) from the inferno.

Lighting our days, warming our bodies, and giving life to everything on Earth, the Sun still holds on to deep secrets to excite the human mind for centuries to come.

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COMING SOON: The First Woman on the Moon: The Past and Future History of Women in Space by James Maynard

The Cosmic Companion

Exploring the wonders of the Cosmos, one mystery at a time

James Maynard

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Writing about space since I was 10, still not Carl Sagan. Mailing List/Podcast:

The Cosmic Companion

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