- 2165
- Why is
the Sun so hot? The Sun’s surface is about 10,000
degrees Fahrenheit. But, surrounding the Sun is an atmosphere of gas known as
the corona. This envelope of super heated gas is called a plasma and it
measures more than 3,000,000 degrees.
Astronomers are still trying to figure out how the outer layer of this
star is so much hotter than what lies beneath it.
-
-
-
------------------ 2165
- SUN - Why
is the Sun so hot?
-
-
The fact that the
Sun is hot should not be news. Astronomers tell us the Sun’s surface is about
10,000 degrees Fahrenheit. But surrounding the Sun is an atmosphere called
the corona. This envelope of super heated gas, which is a plasma, measures more than 3,000,000
degrees. Astronomers are still trying to
figure out how the outer layer of this star is so much hotter than what lies
beneath it.
-
-
The part that confuses scientists is quite simple: Since the Sun’s heat
source is at its core, it should more or less cool as you move farther away
from the center. But, this isn’t what they observe. Science cannot explain how
the corona is so much hotter than other layers that are below it.
-
-
Heat is actually a measurement of how fast atoms are moving. Scientists
are mostly looking for ways to accelerate the Sun's atmosphere material in a
way that happens only in the sizzling corona.
-
-
Despite its heat, the corona is usually hidden from view thanks to the
intense brightness of the rest of the Sun. Even complex instruments have
trouble studying it without being overwhelmed by light from across the Sun’s
surface.
-
- Fortunately
the Sun's corona appears in rare but predictable occurrences that have fascinated
people for millennia, total solar eclipses. In 1869, astronomers took advantage
of just such an eclipse to study the Sun’s suddenly visible outermost layer.
-
-
They used a spectrometer to analyze the light in order to fingerprint
the corona. They spotted an unfamiliar green line that appeared to be a totally
new element, calling it coronium. Seventy years later, scientists realized it
was actually the familiar element iron, heated to never-before-seen
temperatures of millions of degrees. This is hundreds of times the measured
temperature of the Sun’s surface, and was totally baffling to the scientists.
-
-
An early theory was that acoustic waves were compressing and
expanding the Sun’s material like an accordion causing this rise in
temperature. But solar probes haven’t been able to find such waves carrying
enough power to explain the observed coronal heat.
-
-
For almost 150 years, the corona's enormous heat remains one of the
mysteries of science. Scientists are
quite sure their temperature readings of both the surface and the corona are
reasonably correct, and more certain about the basic physics that the
farther you are from a heat source the cooler the temperature should be.
-
-
Part of the problem is that we don’t understand a lot of the small-scale
happenings on the Sun. We know it does its job of heating our planet, and we
know generally how it does it with nuclear fusion. But, the scale of the
materials and forces at work simply don’t exist in a more accessible laboratory
here on Earth.
-
-
Current theories boil down to some version of the Sun being a very complicated
magnet. The Earth spins its own magnetic field. But the Earth, despite oceans
and underground magma, is still much more solid than the Sun, which is just a
big ball of gas and plasma. So the Earth spins more or less like a solid
object.
-
-
Not so the Sun. The Sun spins, but because it’s not solid, its
poles and equator spin at different rates. The Sun also bubbles material up and
down through its layers, like a pot of boiling water. The effect is a tangled
mess of magnetic field lines.
-
-
The charged particles that make up the Sun’s outer layers travel these
lines. The lines snarl and reconnect, releasing massive amounts of energy
exiting as solar flares or leaving twists full of charged particles flying
off into space at ludicrous speed , called
a coronal mass ejection.
-
-
It is possible that underneath what we see, the Sun is undergoing constant nanoflares ,
tiny flares spiking to tens of millions of degrees that cumulatively could give
rise to the corona’s high temperatures.
-
-
A longer-standing explanation have been the existence of acoustic waves.
Heat is just particles moving very quickly. The faster particles move, the
hotter they are. Waves through the Sun’s
interior might fling the Sun’s outermost layer outward. These become acoustic waves, travelling through the Sun like sound waves
travel through air.
-
-
The Sun is full of many different kinds of waves. There are what is called Alfvén waves
that travel in plasma and along magnetic
lines separate from acoustic waves.
-
-
There are many satellites already tracking the Sun. The Parker Solar Probe, launched this
year, 2018, is just starting its
observations. It will continue observing until 2025. Scientists hope that by getting
the closest ever view of the Sun, it will answer some of these questions about
nanoflares or Alfvén waves or, some even
more complicated combination of both mechanisms.
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-
Stay tuned , there is a lot more to learn. I am 78 years and just getting started.
-
- November 13, 2018. An Index of recent Reviews is available.
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--------------------- Tuesday,
November 13, 2018
-------------------------
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