Surface of the Sun
X-ray image of our star, the Sun. (NASA)
is the heart of the solar system and almost all life on earth
gets its energy from the radiation coming from its 10,000 degree
think of the sun as a part of our solar system, but it might be
more correct to think of it as the solar system. Almost
99.86% of the mass of the solar system is tied up in the sun.
All the rest of the solar system - the rocky planets: Mercury,
Venus, Earth and Mars; the gas giants: Jupiter, Saturn, Neptune
and Uranus; the asteroids and dwarf planets like Pluto - only
add up to the measly remaining 0.14 %.
sun is huge. In fact, its diameter is 863,706 miles (1,390,000
km): large enough to fit 1.3 million earths inside of it.
the sun is so large, it has an enormously strong gravity field.
This huge mass, 2,000,000,000,000,000,000,000,000,000,000 kg,
is 300,000 times the mass of Earth. The gravity this mass generates
keeps all the other members of the solar system orbiting around
the sun. In addition, the gravity field also causes huge pressures
deep in the sun's core. This huge pressure (equivalent to 250
billion Earth atmospheres) and high temperatures it generates
in the core (16 million degrees) causes the sun to release energy
through nuclear fusion.
Diameter is 863,706 miles (1,390,000 km).
Temperature: 10,000 degrees Fahrenheit (5,500 degrees C).
4.567 billion years old
70% hydrogen and 28% helium, 2% various other materials.
33.5 days near the poles, 25.6 days near the equator.
The visible surface of the sun is known as the photosphere.
Darker, cooler, sunspots can appear on the surface caused
by the sun's magnetic field.
of nuclear fusion that occurs in the sun is the result of the
nuclei of two hydrogen atoms being forced together. On Earth this
never happens because all hydrogen nuclei are positively charged
and repel each other. In the center of the sun under these extreme
pressures and temperatures, however, two hydrogen nuclei can fuse
together to become a single helium nuclei. In this process, some
of the mass of the original hydrogen is converted to energy. It
is this energy that powers the sun.
second inside the sun 700 million tons of hydrogen is converted
to about 695 million tons of helium. At this rate you might think
that all the hydrogen in the sun would quickly be used up, but
actually scientists estimate that the sun will be able to fuse
hydrogen for at least another 5 billion years without trouble.
At its current age of 4.5 billion years the sun has reached the
point where about 70% of its mass is hydrogen and 28% helium.
from fusion in the core of the sun slowly makes its way to the
surface in a journey that takes between 10,000 and 170,000 years
as the photons carrying the energy are emitted, reabsorbed and
re-emitted again. Eventually it reaches the surface of the sun
which is called the photosphere. Below the photosphere the sun
is opaque to visible light. Above the photosphere is the sun's
atmosphere which is transparent.
the surface of the sun is gaseous, the sun rotates at different
speeds at different latitudes. Near the poles it takes about 33.5
days to go around, while near the equator it rotates every 25.6
spots are places on the surface of the sun have a slightly
lower temperature. Even the smallest ones are about the
size of Earth. (NASA)
the first ways that astronomers came to the conclusion that the
sun rotated at all was by observing sunspots. Sunspots are places
on the surface of the sun where intense magnetic fields have developed
slowing convection (the transfer of heat) from the interior of
the sun to the surface. Because of this sunspots are comparably
cooler and darker than the rest of the sun's surface.
astronomer Gan De observed sunspots as early as 364 BC. In the
17th century Galileo Galilei showed that sunspots were not the
shadow of the passage of the planet Mercury in front of the sun
(as some other astronomers had thought) but were actually marks
on the surface of the sun that moved as the sun rotated. He also
observed that they changed, disappeared, and reappeared over time.
that the sun was not perfect challenged the thinking of the Greek
philosopher Aristotle (who taught that all celestial bodies were
perfect, unchanging spheres) and helped lend support to the heliocentric
(the planets circle the sun) explanation of the solar system.
This, in turn, got Galileo in much trouble with the authorities
at the Catholic church.
of most of the sun is about 10,000 degrees Fahrenheit (5,500 degrees
C). However, sunspots can be as cool as 7,300 degrees Fahrenheit
(4,000 degrees C). Cool is a relative term here, though. Steel
melts at 2,500 Fahrenheit (1,370°C).
of the sun's atmosphere just above the surface is known as the
chromosphere. It's slightly cooler than the surface and is invisible
during normal conditions. However, during a solar eclipse, when
the moon blocks out the bright photosphere, the chromosphere can
be seen as a red ring around the edge of the dark moon.
part of the sun's atmosphere is the corona. It is much hotter
than either the chromosphere or the photosphere with temperatures
as high as 3.5 million degrees Fahrenheit (2 million degrees C).
Scientists don't exactly know why the corona is so hot, but they
suspect it has something to do with the sun's tremendous magnetic
field which is always turning and twisting. The magnetic field
can throw huge plumes (called solar flares) of material from the
sun into space. Some of the material that gets ejected out of
the corona becomes the solar wind. When the sun goes through a
particularly violent set of magnetic field changes, it can create
a surge in the solar wind that causes a geomagnetic storm on Earth.
Such a storm can cause spectacular auroras in the northern and
southern skies, but can also damage the electronics on satellites
and cause disruptions in radio communications.
Sun ejecting a solar flare (NASA).
the sun is the most prominent object in Earth's sky, it is just
one of the billions of similar stars in our Milky Way galaxy.
While it is far from being among the biggest stars, it is brighter
than 85% of them. (Most of the stars in our galaxy are relatively
dim "red dwarf" stars).
stars, the sun has a lifecycle. It is currently about 4.567 billion
years old. Though some larger stars end their lives in a gigantic
explosion known as a supernova, the sun will suffer a quieter
death. When its hydrogen runs low in about 5.4 billion, years
it will start fusing helium instead. This will cause the sun to
expand into what is known as a giant red star. It will become
so big that it will likely engulf Earth's orbit (all life on Earth
will probably be extinct at this point, anyway, because a slow
increase in the sun's heat output will vaporize the oceans in
about a billion years).
the sun will go through a series of expansions and contractions
and lose most of its mass in an expanding cloud known as a planetary
nebula. The core of what is left will become a white dwarf star
which will continue to glow for trillions of years.
2014 Lee Krystek. All Rights Reserved.