Transcript THE PHOTOSPHERE IS THE VISIBLE SURFACE OF THE SUN

THE SUN, OUR NEAREST STAR
STARS ARE FORMED IN GIANT CLOUDS OF
DUST CALLED NEBULA.
EAGLE NEBULA, OFTEN CALLED THE PILLARS
OF CREATION
OUR SUN LIKELY FORMED IN SUCH A CLOUD
4.5 BILLION YEARS AGO - PART OF WHICH
CONTAINED GAS LEFT OVER FROM AN
EXPLODED STAR.
OUR SOLAR SYSTEM CONTAINS ELEMENTS
OTHER THAN HYDROGEN OR HELIUM, AND
THESE ELEMENTS WOULD HAVE HAD TO
HAVE FORMED IN THE CORES OF EARLIER
STARS.
STARS HAVE FINITE LIFETIMES, AND ONE
WAY THEY END IS IN AN EXPLOSION KNOWN
AS A SUPER NOVA.
EVOLUTION OF OUR SOLAR SYSTEM
IN THE CLOUD OF DUST AND GAS, PART
ENDED UP WITH MORE MATERIAL (AND MORE
GRAVITY), SO IT ATTRACTED ADDITIONAL
MATERIAL.
A BALL OF DUST AND GAS FORMED.
AS THIS GREW LARGER, IT STARTED
SPINNING.
A RING OF DUST AND DEBRIS FORMED
AROUND THE MAIN BODY.
A TELESCOPE IMAGE OF A
PROTOPLANETARY DISK
AND AN ARTIST’S IMAGE.
MOST OF THE MATERIAL WENT TO FORM THE
SUN (OVER 99%).
THE REMAINING MATERIAL WENT TO FORM THE
PLANETS.
SMALL OBJECTS COLLIDED TO FORM LARGER
OBJECTS UNTIL MOST OF THE MATERIAL WAS
COLLECTED INTO THE PLANETS.
THIS PROCESS IS CALLED ACCRETION.
IN THE GASEOUS DISK THAT WOULD
BECOME THE PLANETS, GRAVITY SEPARATED
OUT SOME OF THE ELEMENTS, SO THAT THE
INNER PLANETS ARE ROCKY, AND THE OUTER
PLANETS ARE GASEOUS.
ALSO, WHEN THE SUN REACHED IGNITION
TEMPERATURE, THE SHOCK WAVE WOULD
BLOW AWAY ANY GAS IN THE INNER SOLAR
SYSTEM.
ALL OF THE PLANETS WITH THE
EXCEPTIONS OF MERCURY AND PLUTO ARE
ON THE ECLIPTIC.
THE ECLIPTIC IS ALMOST AT RIGHT ANGLES TO THE PLANE
OF THE MILKY WAY GALAXY.
Energy is produced in the sun’s core through nuclear
fusion of hydrogen to helium.
The core is approximately 15,000,000o C.
The sun is mostly hydrogen (92% in terms of number
of atoms, 75% of mass).
Helium is the second most abundant element at 7.8%
in terms of number of atoms and 25% in terms of
mass.
The sun is 0.1% other elements.
The sun makes up 99.9% of the mass of our solar
system.
The sun is not a liquid or a solid. It is a plasma - a
mixture of atomic nuclei and free electrons.
The diameter of the sun is 1.4 million km or about
109 earth diameters. The sun is almost 6,000
times the mass of Earth.
The sun is 93,000.000 miles from Earth (1 au).
The core occupies about about 1/4 of the sun’s
diameter.
In the core, hydrogen is being fused into helium in
nuclear fusion reactions. In this reaction, a small
amount of mass is lost and converted into energy.
Outside of the core, you have the radiative zone
and the convective zone.
Light is emitted in the radiation zone. It can take
photons millions of years to make it out to the
surface, because they keep getting absorbed and
re-emitted.
In the convection zone, cells act like pots of
boiling water with cooler gases sinking and hotter
gases rising.
http://video.nationalgeographic.com/video/science/spa
ce-sci/solar-system/sun-101-sci/
THE PHOTOSPHERE IS THE VISIBLE SURFACE
OF THE SUN.
THE SUN IS COMPOSED OF A GAS OR
PLASMA, SO THINK OF THE PHOTOSPHERE AS
THE DEPTH AT WHICH YOU CAN NO LONGER
SEE TOWARDS THE CORE.
YOU WILL ALSO SEE SUN SPOTS ON THE
PHOTOSPHERE. THESE APPEAR DARK,
BECAUSE THEY ARE ABOUT 2000o COOLER
THAN THE REST OF THE PHOTOSPHERE.
THEY ARE PLACES WHERE INTENSE
MAGNETIC LINES OF FORCE EMERGE FROM
THE SURFACE.
No matter how dark the night, somehow the sun rises
once again and all shadows are chased away.
ABOVE THE
PHOTOSPHERE IS THE
CHROMOSPHERE.
THE CHROMOSPHERE IS
A LAYER OF GAS ABOUT
2500 KM THICK.
IT CAN ONLY BE SEEN
DURING AN ECLIPSE.
IT HAS A REDISH
APPEARANCE BECAUSE
OF HYDROGEN
EMISSIONS.
THE CHROMOSPHERE
HAS A TEMPERATURE
OF 30,000o.
Beyond the
chromosphere is the
corona. The corona
can have temperatures
ranging from 1 to 2
million oK.
The chromosphere and
the corona are not
normallly visible.
Gas flows outward
from the corona as
the solar wind.
Plasma particles flow
out at rates of
approximately 400
km/s.
A PROMINENCE IS A LOOP OF HOT GAS THAT
CAN ERUPT FROM THE SURFACE OF THE SUN
HUNDREDS OF THOUSANDS OF MILES INTO
SPACE.
IT IS HELD IN PLACE BY MAGNETIC LINES OF
FORCE.
The sun is not a solid.
The area around the equator rotates in
approximately 25 hours. The area around the poles
rotates at approx. 35 hours.
This stretches the magnetic lines of force and
results in magnetic disturbances or sun spots.
The sun spots appear dark, but taken in reference
to a normal background, they glow red.
Sun spots are disturbances in the magnetic field.
They can result in coronal mass ejections where
huge amounts of plasma are shot into the solar
system.
http://www.youtube.com/watch?v=tY2n2CHMXfI
THIS VIDEO SHOWS THE SUN’S ACTIVITY
AS SEEN BY NASA’S SOLAR DYNAMICS
OBSERVATORY DURING 2012.
AT THE PEAK OF SOLAR ACTIVITY, 2 OR 3
CME’S CAN OCCUR EACH DAY.
IF THEY COME TOWARD EARTH, THEY CAN
DISRUPT SATELLITE COMMUNICATIONS AND
KNOCK OUT POWER GRIDS.
http://www.youtube.com/watch?v=qLB5ma2Yz1I NASA’s STEREO Sattelites
A GOOD SITE TO USE TO CHECK ON SPACE
WEATHER IS www.spaceweather.com.
THIS SITE GIVES SUN SPOT ACTIVITY AS
WELL AS INFORMATION ON NEAR EARTH
ASTEROIDS.
http://www.nasa.gov/mission_pages/sdo/news/coronal
-rain.html A LARGE SOLAR FLARE
PHOTOGRAPHED BY SDO IN 2012