Our Solar System - Sol (The Sun) Traditional Cache
lyonden_ut: Class is dismissed.
Our Solar System - Sol (The Sun)
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I have seen the Solar System displayed in caches in several
locations around the country and on various scales. For this Solar
System of Caches, I will use the Utah Capital Building as a
stand-in for the Sun.
I will attempt to put the Solar System here in on the Wasatch
Front, on a scale of 1 miles = 1 astronomical unit (AU). An AU is a
unit of length equal to about 149,597,871 km (92,960,000 mi.). It
is defined as the mean distance between the Earth and the Sun over
one Earth orbit.
The following information has been condensed from information found
on Nineplanets.org.
Our Sun is a normal main-sequence G2 star, one of more than 100
billion stars in our galaxy.
diameter: 1,390,000 km.
mass: 1.989e30 kg
temperature: 5800 K (surface) 15,600,000 K (core)
The Sun is by far the largest object in the solar system. It
contains more than 99.8% of the total mass of the Solar System
(Jupiter contains most of the rest).
It is often said that the Sun is an "ordinary" star. That's true in
the sense that there are many others similar to it. But there are
many smaller stars than larger ones; the Sun is in the top 10% by
mass. The median size of stars in our galaxy is probably less than
half the mass of the Sun. The Sun is personified in many
mythologies: the Greeks called it Helios and the Romans called it
Sol.
The Sun is, at present, about 70% hydrogen and 28% helium by mass
everything else ("metals") amounts to less than 2%. This changes
slowly over time as the Sun converts hydrogen to helium in its
core.
The outer layers of the Sun exhibit differential rotation: at the
equator the surface rotates once every 25.4 days; near the poles
it's as much as 36 days. This odd behavior is due to the fact that
the Sun is not a solid body like the Earth. Similar effects are
seen in the gas planets. The differential rotation extends
considerably down into the interior of the Sun but the core of the
Sun rotates as a solid body.
Conditions at the Sun's core (approximately the inner 25% of its
radius) are extreme. The temperature is 15.6 million Kelvin and the
pressure is 250 billion atmospheres. At the center of the core the
Sun's density is more than 150 times that of water.
The Sun's power (about 386 billion billion megaWatts) is produced
by nuclear fusion reactions. Each second about 700,000,000 tons of
hydrogen are converted to about 695,000,000 tons of helium and
5,000,000 tons (=3.86e33 ergs) of energy in the form of gamma rays.
As it travels out toward the surface, the energy is continuously
absorbed and re-emitted at lower and lower temperatures so that by
the time it reaches the surface, it is primarily visible light. For
the last 20% of the way to the surface the energy is carried more
by convection than by radiation.
The surface of the Sun, called the photosphere, is at a temperature
of about 5800 K. Sunspots are "cool" regions, only 3800 K (they
look dark only by comparison with the surrounding regions).
Sunspots can be very large, as much as 50,000 km in diameter.
Sunspots are caused by complicated and not very well understood
interactions with the Sun's magnetic field.
A small region known as the chromosphere lies above the
photosphere. The highly rarefied region above the chromosphere,
called the corona, extends millions of kilometers into space but is
visible only during a total solar eclipse (left). Temperatures in
the corona are over 1,000,000 K.
The Sun's magnetic field is very strong (by terrestrial standards)
and very complicated. Its magnetosphere (also known as the
heliosphere) extends well beyond Pluto.
In addition to heat and light, the Sun also emits a low density
stream of charged particles (mostly electrons and protons) known as
the solar wind which propagates throughout the solar system at
about 450 km/sec. The solar wind and the much higher energy
particles ejected by solar flares can have dramatic effects on the
Earth ranging from power line surges to radio interference to the
beautiful aurora borealis.
The Sun's output is not entirely constant. Nor is the amount of
sunspot activity. There was a period of very low sunspot activity
in the latter half of the 17th century called the Maunder Minimum.
It coincides with an abnormally cold period in northern Europe
sometimes known as the Little Ice Age. Since the formation of the
solar system the Sun's output has increased by about 40%.
The Sun is about 4.5 billion years old. Since its birth it has used
up about half of the hydrogen in its core. It will continue to
radiate "peacefully" for another 5 billion years or so (although
its luminosity will approximately double in that time). But
eventually it will run out of hydrogen fuel. It will then be forced
into radical changes which, though commonplace by stellar
standards, will result in the total destruction of the Earth (and
probably the creation of a planetary nebula).
The Sun's satellites
There are eight planets and a large number of smaller objects
orbiting the Sun. (Exactly which bodies should be classified as
planets and which as "smaller objects" has been the source of some
controversy, but in the end it is really only a matter of
definition. Pluto is no longer officially a planet but we'll keep
it here for history's sake.)
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
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(Decrypt)
Teno n synt.