Page 28 - All About Space 68 - 2017 UK

Mission to touch the Sun

he Sun is the most familiar object in and predictions. Now those theories are to be put to PSP member says…
the heavens. The subject of centuries the test by the Parker Solar Probe (PSP), which NASA
of casual observations and decades describes as a mission to touch the Sun. "We like to call it a giant Frisbee. We had some
of scientific study, it still presents PSP launches in August 2018 (or possibly at the strict constraints about how heavy everything
T something of a mystery. Temperatures very end of July) aboard a Delta IV heavy rocket from could be, so one of the drivers was to figure out
on its visible surface, the photosphere, are about Cape Canaveral, setting out on a seven-year journey not only how to design something that could
5,500 degrees Celsius (9,932 Fahrenheit). Inside, to make 24 orbits of the Sun. On the way, it will make get really hot, but also to make sure that it was
where fusion reactions generate unimaginable seven flybys of Venus, using the planet's gravity lightweight enough that we could actually get
off the ground."
amounts of energy, temperatures reach a hellish to boost it further inwards for its expedition to the
15 million Celsius (27 million Fahrenheit). It might most hostile environment in the solar system. It will Elizabeth Congdon
Lead engineer of thermal protection system
seem obvious that the corona, the star's wispy travel eight times closer to the Sun than any previous
atmosphere, which is visible from Earth only during spacecraft, and become the fastest human-made
a solar eclipse, would be progressively cooler than the object in history as it hurtles around it. The probe's
surface – but it isn’t. Temperatures actually rise back delicate instruments will be protected from roasting
up into the million-degree range over a vast volume by a huge 11.4cm (4.5-inch)-thick carbon composite
of space surrounding the Sun. They reach about 2 heat shield, maintaining the scientific payload at a
million Celsius (3.6 million Fahrenheit) at an altitude temperature that would be comfortable in an office or
of 6 or 8 million kilometres (3.7 or 5 million miles), laboratory on Earth.
a distance equivalent to about ten solar radii above PSP sets another record too: it is the first NASA
the surface. Here, the charged particles that make spacecraft to be named after a living person. The
up the solar wind undergo a bizarre acceleration agency announced in May 2017 that the probe,
propelled by powerful magnetic fields, which previously known as the Solar Probe Plus, would now
increase their speed by a factor of five. The precise be called the Parker Solar Probe, in honour of the
location and nature of these heating and acceleration eminent space scientist Professor Eugene Parker. His
effects are still something of a mystery, with rival 1958 prediction of the existence of the solar wind was
scientific theories offering alternative explanations initially greeted with scepticism, and his scientific
“ It will travel eight times closer to the Sun

than any previous spacecraft, and become
the fastest human-made object in history" The aurora borealis forms when charged particles
from the sun meet the Earth's magnetic shield

Mysteries of the Sun Radiative
zone Understand the
structure and
Why is the Sun’s outermost layer dynamics of the
hotter than its surface? magnetic field
The Sun’s surface is blisteringly hot, The Sun is comprised of a
sweltering at temperatures that hit over complicated magnetic field,
10,000 degrees Fahrenheit, but its which has two poles. They
atmosphere is even hotter. Our current act very much like a bar
understanding is that the further you magnet. The poles flip at
move away from a source, the cooler the the peak of the Sun’s solar
environment gets, however, with the Sun, activity cycle every 11 years.
this is not the case. The team behind the Parker
Solar Probe are interested
in the dynamics of the
magnetic fields where solar
Convective zone flares erupt from
the surface.
Core
Coronal
Chromosphere streamers
© NASA, © Peters &Zabransky, © Kristian Pikner, JHU/APL Why does it unpredictably spew out surface. Being so close to our nearest star, the

Explore the Sun’s plasma
torrents of energised particles?
Interplanetary space is filled with the plasma
that’s expelled via the solar wind, which
These particles impact the Solar System, in particular,
extends from the Sun’s intensely heated
the Earth’s magnetosphere, which creates the aurora.
It also presents a hazard to spacecraft and astronauts,
Parker Solar Probe will investigate the solar
and can trigger storms that have been known to disable
satellites and knock out terrestrial electric power grids
solid, liquid or gas.
for periods of time.
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28 plasma – the fourth state of matter, that isn't a