Getting to the Sun
Some people think that the Sun is only a short
journey from the Earth. But distances, even within the
solar system, are very large. If the Earth were represented
by a ball a foot in diameter, the center of the
Sun would be over two miles away. Getting to the Sun
takes time. With today’s rocket technology, the
journey will take several years.
Protection from the Sun's Energy
Now suppose you're on course for the Sun. How
can you avoid damage caused by the Sun’s intense
light? The designers of the Solar Probe have decided to use a large shield to
protect the spacecraft from damage. This shield places the spacecraft in the
shade. The
diagram to the left shows what the Solar Probe spacecraft
will look like.
The large black oval
is the shield.
The front of this shield casts a large shadow which protects the spacecraft from
the intense sunlight. The back of the shield doubles as a large antenna for radioing
the information back to Earth! Most of the instruments on board are
located in the retractable tail. The materials which make
up the shield need to be tested to be sure that they can
withstand the intense light (which creates heat) of the Sun
without melting or even boiling off into space. The
boiling off process would weaken the shield. It would
also produce a material called plasma that would
confuse the instruments aboard the spacecraft which are
trying to measure plasma material boiled off from the
Sun’s outer layers.
An
artists rendering of the Solar Probe space craft approaching
the active Sun
Plasma, in the astronomical sense of the term, consists
of electrically charged material at very high temperatures.
The temperature is so hot that atoms cease to
exist and become free charged nuclei and electrons. It it
completely different from blood plasma, the liquid part
of our blood.