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The science behind our Sun and its interaction with Earth
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The science behind our Sun and its interaction with Earth
The limited amount of the Sun's energy that reaches Earth gives us heat and light,
without which Earth would be lifeless.
Nicholas Guillerm
Monica Seoane
Alex Reed
Physics 1010
Salt Lake Community College
The science behind our Sun and its interaction with Earth
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Abstract
This paper explores solar research. For thousands of years the human race has felt a
significant connection to the Sun. Although astronomy is as ancient as recorded history itself, it
was long separated from the study of physics. In ancient times people observed celestial bodies
in the sky that seemed to be perfect spheres moving in perfectly circular orbits. Early
astronomers and scientists such as Archimedes (287 BC-212 BC), Nicolaus Copernicus (1473 –
1543), Galileo Galilei (1564 – 1642) and Isaac Newton (1643-1727) were equipped with crude
tools, yet their scientific deductions were brilliant and laid the groundwork for the experimental
researchers who followed them. Recently, through technological and scientific advances,
scientists have uncovered many mysteries behind the Sun's energy. Albert Einstein (1879 –
1955), Carl Sagan (1934 – 1996) and Stephen Hawking (Born 1942) continued scientific
research and made enormous contributions to the ancient study of astrophysics. The availability
of observational data led to research and then to theoretical explanations. The study of our very
own star “The Sun” has a special place in observational astrophysics. Due to the tremendous
distance of all other stars, the Sun can be observed in detail unparalleled by any other star. Our
understanding of our own Sun serves as a guide to our understanding of planets and of other
stars.
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The limited amount of the Sun's energy that reaches Earth gives us heat and light, without which
Earth would be lifeless.
How The Sun affects Life On Earth. Our Sun has lived for approximately 4.6 billion years. It is
about halfway through its lifespan (Frank, 2008). The Sun's light and heat are absolutely vital to
human existence, yet most of us take them for granted. The Sun is the most important factor in
Earth supporting life. We have come a long way in the study of our star, and have learned
much. Understanding our Sun has led to many breakthroughs in science and technology, and in
our understanding of the physical universe. Our Sun, while completely vital to our lives, to the
point that for most of human history it was an object of worship or seen as the center of the
Universe, is for the most part just an average star. There are innumerable stars in the universe,
many far larger than our Sun while many others are smaller. The energy from this glowing
sphere of gas produces climates on Earth capable of supporting life.
The radiant energy given off by the Sun warms and lights Earth, heating its solid and
liquid surfaces as well as its atmosphere. Warmth is distributed because the air in our
atmosphere is always moving. The same is true of our oceans. Water absorbs heat from the
Sun's rays and carries warmth through ocean currents. The Sun also emits radiant energy at a
high frequency, much of which is in the visible portion of the electromagnetic spectrum. We can
therefore observe the effects of light illuminating the Earth. Although we know there are
connections between solar activity and Earth's climate, humans have yet to discover all the
implications of those effects. Only through continued research and a collaboration between
researchers from multiple scientific fields can we gain a more complete understanding.
Photosynthesis is a process by which plant life on Earth converts light energy from the
Sun into chemical energy for fuel. This process allows plants to convert water and carbon
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dioxide into carbohydrates and oxygen creating a well balanced ecosystem. For many millions
of years plant life has evolved the ability to convert energy from the Sun into fuel but now, in a
much shorter period of time, the human race has begun doing the same. With the invention of
solar power technology we are now harnessing sunlight and converting it into electricity through
a process called photovoltaics. Due to the increased demand for renewable and pollution free
energy, the manufacturing techniques in solar panel technology have advanced in recent years
while the cost has declined since the first solar cells were manufactured.
Although the Sun's energy supports life by warming Earth's surface, solar radiation is
deadly to humans. The Earth's atmospheric ozone layer contains carbon dioxide and water vapor
which reflect harmful rays back into space and protect us from extreme temperatures and
ultraviolet light, however some UV rays make it through to the surface. While plant life feeds on
light photons, humans and other animal life can suffer adverse effects from excessive UV
exposure. Too much sunlight can trigger DNA damaging molecules and cause skin
cancer. Solar flares and storms sometimes eject large numbers of highly energetic particles and
X rays towards Earth that our protective layer of atmosphere can not stop. Geomagnetic storms
can damage Earth’s orbiting satellites, and have been known to knock out electrical power and
radio communications over large regions. Among the observable effects of these storms in the
Earth’s atmosphere are the Auroras, geomagnetic disturbances that appear as beautiful lights that
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may drift to lower latitudes, becoming more brilliant and concentrated, as the magnetic force on
the magnetosphere is increased.
Structure of the Sun. The Sun is a giant ball of hot gas that generates energy and releases it into
space in all directions. With the help of Einstein's Special Theory of Relativity, along with the
ideas of other scientists in the late 1930s, the human race learned that the Sun's energy comes
from a process called nuclear fusion, in which mass is converted into energy. Our Sun is just a
typical middle aged, middle sized star that in another 5 billion years or so will exhaust its
hydrogen resources and begin to expand and fuse helium into carbon as it nears its end.
The Sun formed about four and a half billion years ago from a collapsing cloud of
interstellar gas. The contraction of this cloud released gravitational potential energy in the form
of thermal radiation. The remaining energy was trapped inside the cloud causing its interior
temperature and pressure to rise. The cloud reached a state of gravitational equilibrium
becoming capable of sustaining nuclear fusion and the Sun was born. At this point the pressure
of hot gas pushing outward precisely balanced the inward pull of gravity as the energy
generation came into balance with the energy lost from the surface in the form of
electromagnetic radiation.
The source of the Sun's energy is its plasma core, which is one hundred times as dense as
water with a temperature of about 15 million degrees kelvin. The core, while only a fraction of
the Sun's volume, contains half of its mass. Positively charged hydrogen atoms move within the
Sun at very high speeds and collide with one another transforming into helium, while also
generating light photons. Approximately four hundred million tons of hydrogen are turned into
helium each second in the Sun's core.
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The energy from the core radiates outward, passing into the next layer of the Sun, the
radiative zone. Here the heat can only travel as electromagnetic radiation due to the extreme
density and heat of the area. In the radiative zone the energy made in the core, comprised of
gamma rays, radiates out in the form of photons. Throughout the radiative zone these photons
are bounced around so much they make take hundreds of thousands of years to leave the
radiative zone, despite moving at the speed of light. As they bounce, photons lose energy,
becoming less energetic photons. This is fortunate for us as gamma rays aren't exactly good for
us.
Beyond the radiative zone is the convective zone. As the name implies, here the energy
is transferred via convection towards the outer edges of the star. The convection zone is
responsible for the “boiling” of the Sun, and can cause matter to be ejected outwards in solar
flares, also creating the granulated surface that is seen in detailed pictures of the Sun.
The photosphere is the layer of the Sun that we actually see. In general, although the
Sun has no surface, it is the photosphere that is being referred to when we speak about the
surface of the Sun. The diameter of the photosphere is usually used to measure the diameter of
the Sun. It is the coolest part of the star at an average temperature of 6050 degrees Kelvin. The
pressure of the photosphere is very low, for the most part less than 1% the pressure of the Earth's
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atmosphere. It is the layer where electromagnetic radiation is emitted on the spectrum that we
can actually see.
Finally, there are the Sun’s outer layers, the chromosphere and the corona. The
chromosphere is where most of the Sun's hydrogen emissions take place. It is visible during a
solar eclipse as a dim ring around the Sun. Spicules of hot gas erupt above the photosphere with
the temperatures climbing up to 10,000 degrees Kelvin (Franke, 2008). It is believed that this
heat increase in the chromosphere is due to wave motion through the plasma of the
Sun.
The corona is a thin layer of gas, billions of times less dense than that of the atmosphere
of the Earth at sea level, stretching far beyond what we see of the Sun. This is the layer of the
Sun responsible for the solar winds. The corona is heated to 2 million degrees Kelvin
(Franke,2008). It is known that the temperature of the corona is so high because the atoms
observed with in it are found to be highly ionized, which can only occur in the range of millions
of degrees. It is thought that this heating is caused by the solar magnetic field, which can store
and transport energy from the inner regions of the core (utk edu, 2011), but this phenomenon is
not fully understood. Because it is millions of times less bright than the rest of the Sun, the
corona is normally invisible to us, although it can be seen during a total solar eclipse.
Solar activity refers to the array of solar phenomena that can be observed from earth. This
portion of the paper will be dedicated to the observation of three main phenomena: Sun spots,
solar flares, and coronal mass ejection, and the relation between the three.
Among the observable phenomena that occur on the Sun’s surface are sunspots. These
spots are cooler, darker regions on the surface of the Sun created by bundles of magnetic energy
being pushed to the surface. Sunspots are calculated to have a temperature of about 3700K
The science behind our Sun and its interaction with Earth
Figure 1. compared
surface.
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with 5700K for surrounding areas of the Sun’s
The magnetic field of sunspots if calculated to to be almost 1000 times stronger than
the surrounding photosphere. The spots consist of two main parts, these being the “umbra” and
the “penumbra”. Umbra is the darkest innermost region of the sunspot, while “penumbra” refers
to the outer, lighter region. Sunspots are perhaps the most easily observed solar phenomena,
most often appearing in groups or in pairs with negative and positive polarities. Some of the
larger spots can even be observed by the naked eye. Written records on the observation of
sunspots can be traced back to almost 800 B.C. China (Bergman, 2005). They have been
observed throughout recorded history by many curious astronomers who believed they were
seeing clouds on or above the surface of the Sun. Galileo was one of these astronomers, and
was among the first to deduce that the sunspots proved the rotation of the Sun, and the movement
and activity of its surface. Galileo provided drawings of his observations, carefully tracking the
movement of a group of sunspots over a series of weeks, shown in Figure 1 (Van Helden,
1995). In 1843 continuous observation of the Sun eventually lead an amateur German
astronomer, Samuel Heinrich Schwabe, to the discovery of a sunspot cycle. The solar cycle can
be measured in an 11 year span, coinciding with periods of greatest sunspot activity or highest
sunspot count (“solar maximum”), and by contrast, the period of lowest sunspot count, or the
“solar minimum”. This eleven year span periodically reverses, coinciding with the 22 year span
of the Sun’s magnetic field cycle. The Sun’s eleven year cycle is influenced by surface flow,
The science behind our Sun and its interaction with Earth
which is influenced by several
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Figure 2
components. Rotation, oscillation, cellular convection and meridional flow are all contributing
components.
The Royal Greenwich Observatory has provided detailed observations of sunspots since
1874. The data provided by the observatory show that sunspots do not in fact happen at random
but form in concentration in two latitude bands on either side of the equator (Hathaway,
2013). Figure 2 shows the position of sunspots along the equator starting in 1874 and continuing
until 2010. Other phenomena that coincide with the Sun’s 11 year cycle are solar flares. Solar
flares are massive electromagnetic eruptions that occur when magnetic energy that has built up in
the solar atmosphere becomes greatly pressurized and is then released. Solar flares usually occur
near sunspots, in the neutral area between two oppositely directed magnetic fields. Energy
released in a solar flare typically spans almost the entire electromagnetic spectrum, exerting
waves and lengths throughout (Hathaway, 2012). Classification of solar flares is based on their
x-ray light intensity using a series of letters with numerical value, A B C M or X, with A being
the lowest classification, releasing the least intense x-rays, and X being the greatest classification
(Hathaway, 2013).
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Figure 3
Figure 4
Solar flares occur most frequently at the solar
maximum of the 11 year cycle, as this is the time of greatest surface activity. In 1859, Richard
C. Carrington was among the first to record a solar flare that happened to occur during his
observation of sunspots. First believing the flare to be a trick of light entering through a screen,
he then realized that the phenomena was actually happening on the surface of the Sun. After
recording the time, he hastily searched for someone to observe the phenomena with him, only to
return a minute later and realize the moment had passed. Figure 3 displays the points (A and B)
at which “intensely white and bright light broke out…” (Carrington, 1859).
Solar
flares can occur very quickly, as Carrington’s experience proves, but they may also be extended,
decreasing in brightness over hours or even days. These prolonged flares are often accompanied
by another, much larger scale eruption called Coronal Mass Ejections or CME (Figure 4). Figure
4 displays a halo event, in which the entire Sun seems to be surrounded by the expanding
CME. The “halo” occurs when the CME explodes in the direction of Earth. Although CMEs
and solar flares are often observed together, CMEs can also occur independently of an extended
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solar flare. CMEs are large bubbles of magnetized gas which, when exploding, are
comparatively much larger than solar flares. CMEs occur in many variations, some having a
three-part structure, others a narrow jet, and still others appearing as global eruptions. CME’s
essentially remove built up magnetic energy and plasma from the Sun’s corona (Webb &
Howard , 2012). Coronal mass ejections can occur as frequently as several times a day during
the solar maximum, and as infrequently as once every couple of days during the solar
minimum. The magnetized plasma emitted during these eruptions can interrupt the solar winds
creating a shock wave that accelerates solar winds and increases already existing solar
activity. These mass explosions hurdle magnetic energy and particles towards Earth, expanding
as they travel and disturbing the Earth’s magnetosphere, an onrush known as a geomagnetic
storm.
Observation of the connection between the three described phenomena, sunspots, solar
flares and CMEs, helps us understand more about the structure of the Sun and how it distributes
its energy. Learning about the distribution of our Sun's energy allows us to better understand
how more distant stars across the universe work as well. Studying solar activity and the Sun as
the source of life helps expand our knowledge of how the Sun directly affects us on the small
planet we call home.
Quote By Carl Sagan “The Earth and every living thing are made of star stuff”(Carl Sagan,
Cosmos) “The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in
our apple pies were made in the interiors of collapsing stars. We are made of star stuff.” (Carl
Sagan).
The science behind our Sun and its interaction with Earth
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Addison Wesley
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