Ancient people only knew as much about our Sun as they could see with the naked eye.
Today, we have telescopes and other technology that help us make better observations.
But what if we could investigate our Sun up close?
Recently, scientists have designed and launched a probe on its first in human history journey
to the Sun.
So how close did a spacecraft get?
What did it find?
And why didn’t it melt?
Get ready to discover this and some other mysteries of our neighboring star!
INTRO
Without the Sun, no life on Earth would be possible.
But this gigantic ball of hot plasma can also threaten us.
Its bursts of radiation also known as solar flares and its explosive ejections of plasma
called coronal mass ejections accompanied by intense magnetic fields can be frightening.
Even though the Sun’s activity causes spectacular auroras on Earth, spacecraft, satellites,
high-flying airplanes, and even astronauts can be in danger.
Because of solar storms, our telecommunications, navigation systems, and power grids can fail
to properly operate.
We haven’t been able to understand the Sun and how it works, or when it’s going to
throw a massive ball of fiery plasma our way.
This is why scientists have long dreamed of studying our star from a close distance.
We know that the solar wind is a constant stream of charged particles that gains enough
speed to escape the Sun’s outermost layer - the corona.
But we don’t know how energy and heat move through the corona and what accelerates solar
energetic particles.
Astronomers have been seeking the answers to these questions for 50 years, but to no
avail.
Finding answers meant sending a spacecraft through the corona that reaches about 1,100,000
degrees Celsius [2,000,000 degrees Fahrenheit].
And it seemed impossible to accomplish.
Until recently.
This is what the Parker Solar Probe was made for, and it is truly a marvel of human technology.
In 2018, NASA has successfully launched The Parker Solar Probe to revolutionize our understanding
of the Sun and space weather.
The Parker Solar Probe was designed to become the first spacecraft to enter the Sun’s
atmosphere.
It is the size of a small car and it weighs 685 kilograms [1,510 pounds].
The spacecraft has several important instruments onboard.
The Solar Wind Electrons Alphas and Protons Investigation or SWEAP will sample particles
in the solar wind.
The instrument has four sensors that calculate the abundance of particles.
The Wide-field Imager for Solar Probe Plus or WISPR is a telescope that can take 3-D
images of our star’s corona and any structures that pass by the probe.
Another tool that Parker is equipped with is called Integrated Science Investigation
of the Sun [ISʘIS].
It is made of two separate instruments, each having a different energy range.
The instrument can weigh highly energetic heavy ions, electrons, and protons moving
through the Sun’s atmosphere.
Lastly, made of magnetometers and electric-field antennas, The Parker Solar Probe will use
Electromagnetic Fields Investigation [FIELDS] tool to analyze magnetic fields, radio emissions,
and density of the Sun’s corona.
But how can the Parker Solar Probe get so close to our star without melting?
To study the Sun under such extreme conditions, the probe and its instruments are equipped
with a super reflective coating and a shield that measures 2.3 meters [7.5 feet] in diameter
facing the Sun.
The shield called the Thermal Protection System is made of 11.5 centimeters [4.5-inches] of
thick carbon-composite.
This makes the Parker Solar Probe capable of withstanding temperatures outside the spacecraft
that reach roughly 1,370 degrees Celsius [2,500 degrees Fahrenheit].
And even though that might not seem like enough protection, the density of the Sun's corona
isn't high, and not many particles actually hit the probe.
The spacecraft and its instruments are also strategically placed in the center of the
shadow that’s coming from the shield.
The Parker Solar Probe also has sensors to let it know that the heat shield has to be
adjusted when needed.
Another level of protection is located on the inside of the probe.
Parker has a dual array of solar panels and a smart cooling system.
The cooling system circulates water behind the solar cells where it gets heated.
Then, this same water is pushed down into the radiators where it is cooled.
All this makes the Parker probe resistant to heat and radiation like no other space
probe before it.
And even with that level of protection and low density of the corona, Parker can only
stay in this layer of the Sun for a few hours.
But how in the world is it possible to even send a probe towards the Sun?
It's 150 million kilometers [93 million miles] away and would take forever to get there.
Reaching the Sun isn’t that simple.
When a spacecraft is launched into space, whatever velocity rockets give it will be
superimposed on top Earth’s orbital velocity, meaning that we can either cause the spacecraft
to have more or less orbital energy than the Earth does.
We can either boost it to a higher, less tightly bound orbit with respect to the Sun, or deboost
it to a lower, more tightly bound orbit.
Most of our space probe missions use planetary gravity to accelerate spacecraft and give
them more orbital energy.
But, with Parker, scientists needed to do the opposite - make it lose orbital energy.
The Parker Solar Probe has used multiple 'slingshot' orbits using Earth, Mercury, and mostly Venus
to enable it to get this close to the Sun.
And each time it goes around the Sun, the probe picks up an insane amount of speed.
Astronomers call it gravity assist, and it helps Parker narrow its orbit around the Sun
and bring its perihelion about 6.4 million kilometers [4 million miles] closer.
So, did it actually touch the Sun?
Unlike Earth and some other planets, the Sun doesn’t have a solid surface.
But it still has a boundary.
The point where the Sun's gravity and its magnetic forces keep in the solar material
is called the Alfvén critical surface.
According to astronomers’ calculations, it should be anywhere between 10 - 20 solar
radii from the surface of the Sun, which is roughly 7-13.8 million kilometers [4.3 - 8.6
million miles].
And scientists believe that it marks our star's boundary.
With every gravitational maneuver, the spacecraft narrowed its distance to the Sun.
And as it did so, astronomers searched for signs that the Parker Solar Probe had reached
the critical surface.
So what happened when NASA’s spacecraft arrived at its destination?
As the probe passed through a pseudostreamer or a loop-like structure in the corona of
the star, the whirlwind of particles started moving much slower, limiting the impact on
the probe.
This meant that the magnetic fields were dominant in that region so that no particles could
escape it.
It was the proof that Parker was inside the Alfvén critical surface.
The spacecraft then recorded a video of “coronal streamers” moving past it.
It was the first time scientists were able to see these mysterious objects from up close.
The data collected from the probe shows that switchbacks or zig-zag structures in the solar
wind are quite abundant close to our star.
Before, astronomers thought these zig-zag structures were rather an abnormality occurring
near the Sun’s poles only.
But the spacecraft helped scientists conclude that these structures originate in the solar
surface and are quite common.
Parker has also discovered that the critical surface was 18.8 solar radii [13 million kilometers/8
million miles] from the solar surface.
And it took 8 flybys and over 3 years to finally get there.
But this wasn’t the only discovery made by Parker that fascinated scientists.
Multiple flybys near Venus have opened more opportunities to study this hot world.
Until recently, astronomers didn't know exactly what the planet's surface looked like.
Usually, it’s covered with thick clouds.
So a big part of the visible light coming from the surface of Venus is shrouded from
sight.
Parker didn't only manage to record the atmosphere of our Sun but it has also captured Venus’
surface from space.
During its flybys, Parker used its wide-field camera to take images of the entire night
side in wavelengths of the visible spectrum.
[10]
For the first time, scientists were seeing Venus’ surface in visible wavelengths from
space.
Even on the night side, the surface of the planet is roughly 475 degrees Celsius [900
degrees Fahrenheit].
It's so hot that you could see its rocky surface glowing.
So far, the spacecraft has approached the Sun at a distance of 8.5 million kilometers
[5.3 million miles] from its surface.
The previous record was set by the Helios 2 spacecraft in 1976, and the distance was
only about 43.5 million kilometers [27 million miles].
Aside from that, Parker is also breaking space speed records.
During one of its approaches, it was moving at about 700,000 kilometers [430,000 miles]
per hour.
At that speed, it would take Parker about 1 second to get from Philadelphia to Washington
D.C. or less than a minute from New York to Tokyo.
This makes it the fastest human object ever made.
Scientists haven’t found answers to all of their questions yet, but as the spacecraft
enters the Sun’s atmosphere again and again, we’ll find more clues.
The Sun has an 11-year activity cycle during which its stormy behavior intensifies and
then settles back down to a minimum.
And because it currently ramps up, its corona will expand, giving the Parker probe even
more opportunities to enter it again and stay in there for a bit longer.
Eventually, the spacecraft will get as close as 6.1 million kilometers [3.8 million miles]
from the Sun’s surface.
This is just within the orbit of Mercury, which is roughly seven times closer than any
spacecraft has ever approached the Sun before.
The Parker Solar Probe hasn't finished its mission yet.
NASA wants to send the spacecraft deeper into the solar atmosphere to collect more data
about how our neighboring star works.
It will help better understand the phenomena happening inside and around the Sun.
The Sun is the only star we can study from such a close distance and the only one known
to us that can support life.
So if we understand it well enough, we can succeed at searching for life outside our
solar system.
Eventually, the probe and its instruments will start failing and the spacecraft will
melt into a charred piece of metal that will keep orbiting the big glowing ball of hot
plasma.
Its journey will come to an end, but until then, it could surprise us with more fascinating
discoveries.
So, stay tuned as we’ll make sure to tell you everything about that!