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Often, on a clear day, I will briefly glance at the Sun and be in awe about how big and bright
it is in our sky. It’s hard to think that it’s millions of kilometres away, yet it has such a
massive impact on us here on earth. Life would be impossible without the Sun, almost everything
can be traced back to the light and energy it provides. Even though it’s relatively close to
us and not exactly hard to spot, there’s still a lot we don’t know about it, which is why both NASA
and ESA have sent spacecrafts to study the Sun in the last two years. These missions will be the
closest we’ve ever been to our star, so close in fact that they will be able to directly interact
with its atmosphere. So, why are we sending these spacecrafts to the Sun, what will they do there?
What have they found so far? And what makes each of these missions special and unique?
I’m Alex McColgan, and you’re watching Astrum, and in this video we will investigate NASA’s Parker
Solar Probe and ESA’s Solar Orbiter and how they will explore our own magnificent star, the Sun.
The Parker Solar Probe was announced in 2009 and was launched on August 12th,
2018 on a Delta IV Heavy rocket. It will use seven Venus flybys over nearly seven years
to gradually shrink its orbit around the Sun. At its closest point, it will only be about 6.16
million kilometres (3.8 million miles) away, which is inside the Sun’s corona or its atmosphere.
Being that close would feel like 500 Suns in the sky beating down at the same time,
with the temperature reaching up to 1,400 °C (2500°F). The spacecraft is going 7 times
closer to the Sun than any spacecraft has ever gone before, and at these temperatures
many components that are used to make sensitive equipment for spacecraft would melt away.
To protect the spacecraft and all its equipment, it is shielded by an 11 cm thick
carbon-composite shield, which can withstand these high temperatures.
This shield also has a white reflective surface that can help minimise heat absorption. This
shield will always be facing the sun, protecting the spacecraft in this harsh environment.
Being far away from Earth, and orbiting a very dangerous object, this spacecraft is by necessity
as autonomous as a space mission has ever been. Because the heat shield always has to be facing
the Sun, for large sections of its orbit it won’t be able to point its antenna at Earth.
During these times of communication blackout, it will control each of the sensors, control
the formatting of data products, and archive high-resolution data, until it can communicate
with Earth again and transmit back what it has captured. ESA’s Solar Orbiter mission began
development in 2012 and after 8 years, the Solar Orbiter was launched on February 10th,
2020 on an Atlas-V rocket. The Solar Orbiter will also use gravity assists from Venus as well as
Earth. These swing-bys will put the Solar Orbiter into an initial 180 day orbit around the Sun.
The spacecraft will reach the closest approach to the Sun every six months, at around 43 million
kilometres away. This is comparatively much further away than the Parker probe’s closest
approaches, but just to give you an idea of the temperatures at this distance still,
at 43 million kilometres from the Sun, the temperatures can reach up to 500°C (932°F) as the
sunlight will be 13 times more intense than what we feel on Earth. The Solar Orbiter is protected
by a heat shield made with titanium foil layers about 40 cm thick, which is not as effective as
the Parker probe’s heat shield but still enough to protect the spacecraft on its dangerous mission.
It is surprisingly difficult to get a probe into a close orbit around the Sun,
as it takes 55 times more energy to go to the Sun than it does to go to Mars. You see,
the Earth is always moving sideways relative to the Sun, at very high speeds, about 30 kilometres
per second (19 mph) or 108,000 kilometres per hour (67,000 mph). In order for a probe to
successfully enter into an orbit around the Sun it must cancel out almost all of that motion.
This is why both the Parker and Solar Probes were launched using two of the
most powerful launch vehicles available at the time, the Delta-IV and Atlas-V.
The objectives of the Parker Solar Probe and the Solar Orbiter are similar to a great extent.
Both these missions aim to find out more about our Sun's corona, its solar winds, coronal mass
ejections, the structure of the Sun's magnetic field and simply how it all fits together.
The Sun, like all stars, is a ball of plasma. Plasma is superheated matter – so hot that the
electrons are ripped away from the atoms, leaving an ionized gas. The Sun has an atmosphere of
extremely hot but tenuous plasma extending out for millions of kilometres called the Sun’s corona.
You can see the plasma atmosphere in this image, although typically it is far harder to see than
the Sun itself, as the Sun’s outer layer, known as the photosphere, is much brighter.
The ideal time to spot the Sun’s corona is during a solar eclipse, when the Moon blocks
out the photosphere disk, leaving just the wispy arms of the corona visible. The strange thing
about the Sun’s corona is that its temperature is between 1,000,000°C (1,800,000°F) and 3,000,000°C
(5,400,000°F), whereas the Sun’s surface temperature is only about 5,500°C (9932°F),
and currently we don’t really know why. And while the Sun’s corona looks substantial,
it’s brightness is deceiving. It is actually magnitudes less dense than Earth’s atmosphere!
The Sun continuously releases huge amounts of charged plasma and radiation into space, which
is known as the solar wind. Solar wind is not very strong or dense, and the Earth's magnetic field
diverts most of it harmlessly away. While a lot of solar wind does get redirected around the planet,
some gets funnelled towards the planet’s poles, where ions from the solar wind
collide with atmospheric oxygen and nitrogen atoms, the interactions of which emit the
beautiful colours we see in auroras. The number of particles ejected by the Sun is not constant.
Reconnection events in the Sun’s magnetic field can release huge amounts of energy in the corona,
ejecting millions of tons of charged particles into space in one big eruption. This is what is
known as a Coronal Mass Ejection, or a CME. When these CMEs interact with the Earth’s magnetosphere
it causes what's called a geomagnetic storm, and the biggest of these storms can be devastating.
The largest geomagnetic storm ever to hit Earth was the Carrington Event back in 1859. If such
a CME was to hit earth now, the resulting storm could affect satellites and our electric power
supply, in what could be described as a hemisphere wide EMP bomb. As we depend on electricity and the
internet so much, even a few hours of outage could cause serious problems. Some estimates show that
if a Carrington sized event happened today, it could cause a few trillion dollars in damages.
And unfortunately, CME flares are fast, they have been shown to reach Earth in just 17 hours.
This might not be enough time to alert the entire population, turn off reactors,
and take necessary precautions. In reality, we have simply been lucky up until this point,
as we missed a Carrington sized event hitting us by just a margin of nine days in July of 2012.
Had it been 9 days later, Earth would have been a bit further in its orbit and in the CME’s path.
This is why it’s so important for us as a delicate species to understand the Sun’s corona, so we can
better predict solar storms, to give us better warning and hopefully avoid damages associated
with a Carrington sized event actually hitting us. It’s just a matter of when rather than if.
Now, these two probes may seem similar, and while a lot of their goals do overlap,
they both have some unique features. The Parker probe is going deep into the Sun’s corona,
where no man-made object has gone before. Because it has to withstand such high temperatures,
the spacecraft is limited in some ways. For example, it cannot take any pictures of the Sun,
as no current camera technology could directly look at the Sun from that close and survive. But
the Parker probe has instruments that can directly sample and collect data about the particles that
exist in the Sun’s corona and even closely study the regions where solar winds originate,
something that can’t be done at a distance. The Parker probe is lighter, smaller and has less
equipment when compared to the Solar Orbiter. The Solar Orbiter on the other hand carries both
particle detectors and telescopes. It can take close-up pictures of fascinating solar landscapes,
and due to its orbit, it will be able to track a region of the solar atmosphere for much longer
than is possible from Earth. This will enable it to observe storms building up in the atmosphere
over several days. So, as you can see, these probes are complementary,
and both will help further our understanding of the Sun’s corona in their own way.
So, what have these missions achieved so far? Well, on 27 September 2020, the Parker Probe
passed within 13.5 million km of our star, the closest any spacecraft has ever been. Also,
it became the fastest travelling human-made object ever, travelling at 466,592 kmph (289,927 mph).
And this isn’t even as close or as fast as it’s going to get.
Still, even at this distance, the data sent back from the Parker Probe is already helping our
understanding of how the Sun’s magnetic field and the corona interact to form solar winds. The probe
also discovered that some magnetic fields from the sun sweep through the solar atmosphere, which
can increase the solar wind speeds by as much as 500,000 kmph (300,000 mph). In addition, it has
discovered evidence of a cosmic dust-free zone 5.6 million kilometres (3.5 million miles) from the
Sun. It’s believed this is due to the vaporisation of cosmic dust particles by the Sun's radiation.
The Solar Orbiter has already sent back its first images of the Sun and scientists found something
called ‘campfires’, which you can see here. These are explosions on the Sun's surface that occur as
a result of disturbances in small magnetic fields. The Solar Orbiter also took the closest images in
existence of the Sun’s surface from 77 million km away (48 million miles). And the examination
of particles across its orbit will help us better understand the different types of space weather.
So, all in all, these missions still have exciting times ahead. Getting ever closer to the Sun will
help us understand it like never before. Want to keep up to date with these amazing mission’s
finding as they happen? Then be sure to subscribe for more. Does space inspire you to learn like it
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Thanks for watching! If you enjoyed this video about the Parker probe and the Solar orbiter
missions, be sure to like and subscribe, and also check out some other spacecraft video here. A big
thank you as well to my patrons and members who support the channel. If you would like to support
too, check out the links in the description below. All the best and see you next time.