Our Sun
Our Sun – The Abnormal Star
Fact – our Sun is a star
Average in size
Commonly called a “Yellow Dwarf”, the Sun
is actually white when viewed from space
Middle Age for a star
But it is not part of a multiple star cluster!
Anatomy of the Sun
Chromosphere
TABLE 16.1 The Standard Solar Model
INNER RADIUS
TEMPERATURE
DENSITY
(km)
(K)
(kg/m3)
DEFINING
PROPERTIES
Core
0
15,000,000
150,000
Energy generated by
nuclear fusion
Radiation zone
200,000
7,000,000
15,000
Energy transported by
electromagnetic radiation
Convection zone
500,000
2,000,000
150
Energy carried by
convection
REGION
10-4
Electromagnetic radiation
can escape—the part of
the Sun we see
Photosphere
696,000*
5800
2
Chromosphere
696,500*
4500
5 10-6
Cool lower atmosphere
Transition zone
698,000*
8000
2 10-10
Rapid temperature
increase
Corona
706,000
1,000,000
10-12
Hot, low-density upper
atmosphere
10-23
Solar material escapes
into space and flows
outward through the solar
system
Solar wind
10,000,000
2,000,000
Core
In solar astronomy, the innermost part of the
Sun is where energy, in the form of gamma
ray photons, is generated by nuclear
reactions. It takes anywhere between
10,000 to 170,000 years for these photons
to make their way to the Sun’s surface.
Nuclear Fusion
in the core
The process by which
multiple like-charged
atomic nuclei join
together to form a
heavier nucleus.
The proton–proton
chain reaction
dominates in stars the
size of the Sun or
smaller.
In this reaction,
hydrogen fuses to
create helium and
release energy.
At the current rate of
fusion, the Sun should
continue to burn for
another 5 billion years.
Radiative Zone
An interior layer of the Sun, lying between
the core and the convection zone. Photons
travel outward by radiation in what is
described as a “drunkard’s walk” as they are
absorbed and then re-radiated over and
over again in many different directions.
Convective Zone
The layer of the Sun between the radiative
zone and the photosphere where energy
travels outward by convection. At this point,
the gamma ray photons have been slowed
down considerably and have been converted
to lower frequency photons of light and heat.
Photosphere
The visible surface of the Sun.
It is a layer of gas that is
heated enough to shine.
It is the layer from which the light we
actually see (with the human eye) is
emitted.
It is also the layer astronomer’s refer to
as the Sun’s “surface.”
Chromosphere
The layer above the photosphere and
beneath the transition region and the corona.
The chromosphere is hotter than the
photosphere but not as hot as the corona.
Corona
The outer layer of the sun. It
looks like a halo and is visible
during eclipses or from special
telescopes. Extends about a
million miles out into space.
Circulation in the Sun
Electromagnetic Radiation
Energy created in the core radiates out
through radiative (radiation) zone.
Next, it moves from the core through the
convective (convection) zone.
Finally, it exits the Sun’s atmosphere.
Features of the Sun
Sunspots appear as dark areas
on the solar surface, contain
strong magnetic fields that are
constantly shifting. A moderatesized sunspot is about as large
as the Earth. Sunspots form
and dissipate over periods of
days or weeks. They occur
when strong magnetic fields
emerge through the solar
surface and allow the area to
cool slightly, from a background
value of 6000 ° C down to
about 4200 ° C; this area
appears as a dark spot in
contrast with the very bright
photosphere of the sun. The
rotation of these sunspots can
be seen on the solar surface;
they take about 27 days to
make a complete rotation as
seen from Earth.
http://www.nasa.gov/mission_pages/sunearth/spaceweather/
Sunspots
Size comparison of
Earth to a sunspot
11-Year
Solar
Cycle
Prominences
Loops of cool
plasma that link
different parts of
sunspots.
Image via NASA
A solar
prominence
is vast and
awesome in
size in
contrast to
our little
Earth. But
the Earth is
so far from
the sun that
these
prominences
pose no
danger.
Prominences
Huge, high-arching
plasma columns
Solar
Flares
May occur when
prominences loop together,
or sunspots move together.
This produces a very violent
eruption on the surface of
the sun called a solar flare.
CME’s
Coronal Mass Ejections
Large amounts of electrically charged gas
suddenly ejected from the Sun’s corona.
CME’s
During periods of sunspot
maximum, CME’s can occur
two or three times each day.
CME’s
http://www.mnn.com/earthmatters/space/stories/stunning-coronalmass-ejection-erupts-from-sun-photo
CME’s may appear as a bubble bursting out of the sun.
They cause magnetic storms, which damage satellites, interfere with radio
signals, and can damage electrical grids.
CME’s
CME’s – The Impact to Earth
Solar Wind
The outflow of
charged particles from
the Sun’s corona.
Aurora Borealis
When CME’s, in the form of a solar wind, interact with our
magnetosphere, they can produce the light show called an Aurora.
The charged particles carried by the solar wind generate electric
currents at the poles. These currents ionize gases in the atmosphere,
which produce the lights.
Solar
Storm
Geomagnetic storm produced by solar
flares, CME’s or coronal holes. Can
affect satellites, communication and
navigation systems, and electrical systems.
The Light year!
The distance light travels in one year in a vacuum
Light travels at 300,000 km/sec or 186,000 mi/sec
1 light year = 9,460,730,472,580.8 km
(That is approximately 9.5 trillion kilometers or 5.9 trillion miles!!!)
The distance from the Earth to the Sun is approximately
150,000,000 kilometers, or 93,000,000 miles.
So then, how many light years is it
from the Earth to the Sun?
Moon
16.5 day
9.4 hours
Sunbeam (186,000
miles/second)
1.2 seconds
Sun
17 years, 8 months
4 months
8.5 minutes
Mercury
10 years, 10 months
3 months
5 minutes
Venus
5 years, 5 months
1.5 months
2.5 minutes
Mars
8 years, 10 months
2.5 months
4 minutes
Jupiter
74 years, 3 months
1 year, 9 months
35 minutes
Saturn
150 years, 5 months
3 years, 7 months
1 hour, 11 minutes
Uranus
318 years, 6 months
7 years, 7 months
2 hours, 30 minutes
Neptune
513 years, 2 months
12 years, 3 months
4 hours, 2 minutes
Pluto
Alpha Centauri
(nearest star)
Sirius (Dog star)
690 years, 1 month
16 years, 5 months
5 hours, 25 minutes
4.8 million years
114, 155.2 years
4.2 years
9.6 million years
228,310.4 years
8.4 years
Destination
Jet (600 mph)
Rocket (25,000 mph)
Pleiades Cluster (7
Sisters)
400 years
Catherine (AKA
Crab) Nebula
4,000 years
Center of the Milky
Way
38,000 years
Andromeda Galaxy
2.2 million years
Solar Facts
* Average distance from Earth: 93 million miles (150 million kilometers)
* Radius: 418,000 miles (696,000 kilometers)
* Mass: 1.99 x 1030 kilograms (330,000 Earth masses)
* Makeup (by mass): 74% hydrogen, 25% helium, 1% other elements
• Average temperature: 5,800° Kelvin (surface),
15,500,000 ° Kelvin (core)
* Average density: 1.41 grams per cm3
* Volume: 1.4 x 1027 cubic meters
* Rotational period: 25 days (center) to 35 days (poles)
* Distance from center of Milky Way: 25,000 light years
* Orbital speed/period: 138 miles per second/200 million years
Nuclear Fusion
Hydrogen to Deuterium
Deuterium to Helium-3
Helium-3 to Helium
Corona - 1,700,000° C
Chromosphere - 27,800° C
Photosphere - 6,000° C
Convective Zone
Anatomy of the Sun
Radiative Zone
To convert °C to °F
°F = (°C X 9/5) + 32
The CORE – 15,000,000° K
Nuclear Fusion
The process by
which multiple
like-charged
atomic nuclei join
together to form a
heavier nucleus.