(wondrous ambient music)
Our sun is a star
like billions of others throughout the universe.
It's a giant nuclear furnace
at the center of our planetary system.
And although life on earth
is completely reliant upon the sun,
we also need our planet's magnetic field
and atmosphere to protect us
from extremes of solar radiation.
Regularly, the sun ejects huge blasts of solar plasma.
And on earth, a direct hit by a coronal mass ejection
will play havoc with power grids,
communications, and satellites.
(wondrous orchestral music) (intense whooshing)
1859 was a year of extreme solar activity.
During September of that year,
Astronomer Richard Carrington was sketching sunspots
when he observed an intensity bright event.
Less than 18 hours later,
auroras were seen around the world.
They extended to low latitudes
where the phenomenon is rarely seen.
Telegraph operators across Europe
and North America reported malfunctions
including electric shocks and sparking wires.
This was the first time that solar storms
had been linked with auroras
and electrical and magnetic disturbances here on earth,
and it became known as the Carrington effect.
Since the 1700s,
a periodic fluctuation had been observed
in the number of sunspots,
but a deeper insight into the sun's behavior
would not emerge until 1958.
James Van Allen was the chief scientist
for America's first satellite, Explorer 1.
It was equipped with a cosmic ray detector.
Eight, seven, six,
five, four, three, two, one.
Fire, command! (explosion blasting)
The launch was successful,
but the orbit achieved was highly elliptical
with an apogee far greater than expected.
As its altitude changed,
variation in the detector's readings
suggested that charged particles
were trapped in bands around the earth.
These became known as the Van Allen belts.
(audience applauding)
It was a discovery with far reaching implications.
The energetic charged particles
that make up the Van Allen belts emanate from the sun
and are trapped by the Earth's magnetic field.
They fluctuate with solar activity
and they present a risk to spacecraft
that have to pass through them.
The previous year,
Physicist Eugene Parker,
working at the University of Chicago,
had predicted that a constant stream of charged particles
would flow from the sun.
He called it the solar wind.
The astronomical community was reluctant
to accept this idea.
Soon, his theory was vindicated
as early Russian and American spacecraft
began detecting a constant stream of charged particles.
Solar wind explained why a comet's tail
always points away from the sun.
Parker's supersonic solar wind theory
predicted a variable stream of plasma,
charged particles, permeating the solar system.
The Earth's magnetic field deflects most of the solar wind,
preserving the Earth's atmosphere.
In 1995,
the Solar and Heliospheric Observatory was launched.
SOHO monitors the sun from a point
where the gravity from Earth
and from the sun exert equal force,
keeping the probe in a stable orbit.
SOHO gives us a clear picture of the solar wind.
Its LASCO instrument obscures the central disc of the sun,
revealing the corona, the sun's atmosphere.
The planets are also clearly visible.
The horizontal lines flanking them
are due to their brightness
overwhelming the camera's sensor.
SOHO's extreme ultraviolet imaging telescope
was able to see waves traveling out from solar flares,
causing snow-like interference in the image sensor.
Solar radiation in the extreme ultraviolet
varies from minute to minute
and over the sun's 11 year solar cycle.
Solar activity generates tides in the Earth's atmosphere,
which increase with altitude.
This in tern at the drag felt by low orbiting satellites.
Communication systems can also be affected,
in particular GPS services.
Constantly monitoring the sun's behavior is important.
And in 2010, NASA launched the Solar Dynamics Observatory.
It orbits the Earth geosynchronously
at an inclination of 28 degrees,
which gives it a constant view of the sun.
The SDO observes in a number of different wavelengths
that correspond to different temperatures,
each one revealing varying activities
from the surface, to the corona,
and to the flaring regions.
The sun is not solid.
Rather than rotating, it swirls.
At the equator, it spins once every 25 days.
At the poles, it takes 38 days.
It's in a plasma state,
extremely hot matter made up of loose electrons and ions.
Plasmas are excellent conductors of electricity
and the movement of the sun
generates a tangle of magnetic field lines.
The surface of the sun, known as the photosphere,
has a temperature of around 6,000 degrees Kelvin
and is best viewed in the visible part of the spectrum.
Here, sunspots appear as dark regions
where magnetic flux impedes convection.
These are about the size of the Earth.
Beyond the visible spectrum,
magnetic loops at the same areas become visible.
The lower levels of the sun's atmosphere, the chromosphere,
see gravity yielding to the dynamic thermal
and magnetic forces,
with temperatures increasing to 8,000 degrees Kelvin.
Ascending further through the solar atmosphere,
a narrow band called the transition region
sees temperatures rise to more than 500,000 degrees Kelvin.
In the corona, seen here during an eclipse,
it rises to a million degrees Kelvin.
Why this happens is not understood.
The atmosphere is where the solar weather is generated.
Solar flares appear as bright flashes,
bursts of electromagnetic radiation
from radio waves to gamma rays.
Solar flares from some other stars
are much larger than those from our sun.
And sometimes, smaller stars known as red dwarfs
display extreme solar flares.
The Swift Gamma Ray Observatory is designed
for rapidly locating brief bursts of gamma rays and X-rays.
In April, 2014,
Swift saw a solar flare emanating from DGCVn.
Its initial blast was 10,000 times stronger
than any flare from the sun.
It was the first of seven flares
that continued for two weeks.
DGCVn is a red dwarf about one third the size of the sun
and it rotates twice as fast as the sun.
This enables it to generate a much stronger magnetic field.
It's thought that the strength of the star's magnetic field
is related to the intensity of the flares it emits.
Coronal mass ejections are different.
They are vast clouds of plasma
blasted from the sun's outer layers.
They travel with the solar wind.
While they are often linked with solar flares,
researchers have not been able to establish
a direct relationship.
Observing the sun in different wavelengths
yields very accurate temperature readings,
and the dramatic rise in temperatures
moving away from the surface
had scientists completely baffled.
Five, four, three, two.
In 1990, a new spacecraft was launched.
Ignition and lift off of Discovery
and the Ulysses Spacecraft
bound for the polar regions of the sun.
The Ulysses probe was bound for the sun,
but had to go the long way.
Solar researchers wanted
to have a different view of our star.
The solar system coalesced
from a vast cloud of gas and dust.
As it collapsed, it began to spin, forming a disc.
all the planets orbit along the plane of this disc
called the ecliptic.
Ulysses would look at the poles,
the parts of the sun that could not be seen
from our terrestrial viewpoint.
Ulysses traveled via Jupiter
using the giant planet's strong gravitation
to change its course.
It approached on a path
that took it over the planet's north pole.
This bent the probes' trajectory beneath the ecliptic
so that it could see the sun from a polar orbit.
From Ulysses,
we learned that the sun's magnetic field
reverses every 11 years,
and that the solar wind from the more dynamic south pole
was faster than from equatorial regions,
yet the south pole had no clear location.
The only thing clear about the sun
was that it keeps changing.
Now, heliophysicists wanted to be able
to see the face of the sun that was not seen from Earth.
Liftoff of the Delta II rocket STEREO,
giving us a three-dimensional look
at the physics of our sun.
The twin stereo probes were launched in 2006.
They were in slightly different orbits,
one leading the Earth and moving slightly faster,
the other trailing the Earth and moving slower.
Each year, the two craft separated by 44 degrees,
giving each an increasingly different view of the sun.
Because the sun rotates,
sunspots can develop out of sight.
As sunspots are key indicators of solar weather,
it's important to know just what is about to spin into view.
The STEREO probes now observe the sun in 360 degrees.
This makes it much easier
to plot the direction of coronal mass ejections.
Though these happen with reasonable frequency,
most will miss the Earth.
If they hit,
they create havoc in electrical systems
and trigger substorms in the planet's magnetosphere.
Information provided by the STEREO satellites
is being used for the protection of power grids
and satellites through regular space weather bulletins.
Since the 1960s,
observers have been aware
that auroras would sometimes brighten suddenly
with movement within the auroral curtains increasing.
These were short term phenomena,
quite distinct from solar storms
that result in auroral activity lasting days.
As communications satellites
in geosynchronous orbits became more sophisticated,
they registered sudden localized falls
in the Earth's magnetic field
that seemed to coincide
with what were now being called substorms.
Three, two, one.
We have ignition and liftoff of a Delta II rocket
carrying THEMIS,
NASA's revolutionary journey to study the northern lights.
The THEMIS constellation of satellites
was designed to monitor the behavior
of the Earth's magnetosphere.
The aim was to measure fluctuations
within the Earth's magnetic field
and relate any variations
to changes detected in the auroras
from ground stations in the North American arctic.
Each satellite was equipped with an array of booms
to measure the strength
and direction of electrical and magnetic fields.
After several months,
they maneuvered into elliptical orbits
of varying eccentricity,
with each reaching a high point
above the night side of the earth.
The Earth's magnetic field deflects
most of the plasma from the sun.
At times of high solar activity,
some of the charged particles
will spiral into the poles on Earth's day side.
On the night side,
the field lines are stretched to breaking point
called magnetic reconnection
when the plasma suddenly rebounds along the field lines
into the polar regions.
In February, 2008,
two of the probes detected a reconnection event
and 96 seconds later,
the ground stations registered
a sudden brightening of the aurora.
The giant loops bursting from the sun's surface
are known as flux ropes.
They're one of the most basic configurations in plasma.
The glowing plasma follows helical magnetic field blinds,
twisting around a central core.
The THEMIS satellites discovered that flux ropes
can extend all the way from the sun
to the Earth's upper atmosphere,
carrying currents as high as 650,000 amps.
Heliophysicists remained baffled
by the behavior of the sun's atmosphere,
so a new probe was constructed.
Known as IRIS, it was small and simple.
It consisted of a telescope,
an imaging spectrograph,
and ancillary support equipment.
It was cheap to build and cheap to launch.
IRIS was placed in a polar orbit of the Earth
that gave it an uninterrupted view of the sun.
It was able to look at the edge of the chromosphere
where the plasma began its steep increase in temperature.
Its images were far more detailed
than had been delivered by any other probe
and it could discern rapid changes.
The waving jets of plasma called spicules
were revealed in great clarity.
There are roughly 10 million spicules
across the sun's surface at any given moment.
They can grow to 10,000 kilometers,
yet they collapse in five or 10 minutes.
Researchers have made computer models of the spicules
that behave in the same way as the images from IRIS.
It is thought that they form
through the interaction of charged and neutral particles
with the tangled magnetic fields.
It seems magnetism must play an important role
in the heating of the solar corona
and in the high-speed ejection of plasma,
but the mechanism is still not understood.
There are at least 20 different satellites
currently monitoring the sun's behavior.
Most are in orbit around the Earth.
While it is important to get to beyond the earth atmosphere
to analyze the solar wind,
it has not been possible to get really close to the sun.
Heliophysicists know the particles of the solar wind
change not long after they leave the corona.
If these particles could be sampled close to the sun,
it would reveal what part of the solar atmosphere
was responsible for their extreme heat
and their ultra high speed.
Until recently,
it was not possible to build a craft
capable of withstanding the temperatures
in regions that scientists wish to explore.
The team behind the MESSENGER probe to Mercury
solved some of these problems
with a woven ceramic sun shield
which had to face the sun at all times.
Around 2010,
work began on Solar Probe+,
designed to pass the sun
just six million kilometers above its surface.
A number of different systems have to work in concert
to enable the probe to gather data
inside the sun's atmosphere.
A carbon composite solar shield
surfaced with highly reflective alumina
will shade the rest of the craft from temperature extremes.
As the sun is a wide band radio source,
the probe is out of contact during its close approaches
and must function autonomously.
In 2017, the probe was renamed the Parker Solar Probe
after Eugene Parker,
the physicist who had first identified the solar wind.
It was the first spacecraft
to be named after a living person.
On a mission like this in the new territory,
you're gonna be in for some surprises.
Maybe not big ones, maybe only little ones,
but you're gonna find that your point of view
will have to change to conform with the data.
Why is the solar corona,
the outer atmosphere of the sun
at a million or two degrees
when the sun itself is only 5,600?
It isn't because of sunshine, that's for sure.
Again, we don't know until we make the flight
and have a year or two to think about the data.
The Parker Probe's launch weight
is less than 700 kilograms,
which is quite modest.
Yet its launch vehicle, the Delta IV Heavy,
is one of the most powerful boosters available.
Minus 15.
In the pre-dawn hours of August the 12th, 2018,
the final countdown was proceeding.
Eugene Parker was at Cape Canaveral to watch the launch.
Three, two, one, zero.
Liftoff.
(explosion blasting) Wow!
The probe was headed
for 26 highly elliptical solar orbits over seven years.
During its mission,
it will make seven close passes of Venus,
slowing each time to sweep closer and closer to the sun.
After separation from its upper stage,
the probe first deployed its solar panels.
These fold back near the sun
with a cooling system enabling them to survive.
The magnetometer boom unfolded at the rear of the craft
and then the field antennae,
to measure electric and magnetic fields and waves,
snapped into place.
Though the Parker Probe leaves Earth at high speed,
it uses Venus's gravity to slow down,
allowing it to approach the sun at the appropriate angle.
However, as it falls toward the sun,
it will accelerate to 720,000 kilometers per hour.
On its outward loops, it will lose speed,
but as the mission progresses,
the Parker Probe will make closer passes at higher speeds.
It made its first close approach of Venus
after just 52 days.
One month later, Parker approached the sun.
For 11 days, it was out of contact with mission control,
quietly recording data
while carefully keeping its sunshield
pointed directly at the sun.
Though the heat in this region is extreme,
the particle density is not.
The sunshield will reach around 1,500 degrees Kelvin
and the protected electronics of the spacecraft
will be at room temperature.
As the probe loops away from the sun,
it's able to re-establish radio contact
and playback the stored data.
This is the first image from inside the sun's corona
taken during Parker's first pass.
It shows a coronal streamer.
The bright spot is the planet Mercury.
The dark spots are image correction artifacts.
The Parker Probe's second and third passes
were at much the same distance and speed as the first,
but subsequent passes will be both lower and faster
as it continues to use Venus to modify its orbit.
In 2024, the Parker Solar Probe
will visit Venus for the last time.
And its final five passes of the sun
will come down to 6.2 million kilometers from the surface.
By this time,
we should have a clearer understanding of the processes
that heat the solar wind and expel it at such high speeds.
But whatever we learn about our sun,
it will raise new questions.
A clearer understanding of the sun
has led to design changes in satellites
and revised management practices of power grids
and communication systems.
But with new proposals to send humans back to the moon
or on planetary expeditions,
we will need to understand more
about the potentially hostile solar weather
that flows from the star we call our sun.
(contemplative orchestral music)