Transcript sun elements

Scale of the Sun's Energy
• In just one second the Sun emits more energy than humans
have used in the last 10,000 years.
•The Sun has been shining relatively steadily for 4.6 billion
years. Until the early 20th century, humans did not know of
any process that could explain the energy production of the
Sun.
•Even if a fire, such as those that occur on Earth, were as large
as the Sun, the fire would consume the mass of the Sun in a
few thousand years.
The Sun's Energy
• The Sun produces an amazing amount of light and
heat through nuclear reactions.
•The process that produces the Sun's energy is called
nuclear fusion.
•In nuclear fusion, two atoms come together to produce
a heavier atom.
•Fusion reactions release energy and tiny elementary
particles.
How does fusion happen?
• The Sun is a massive amount of hydrogen, the lightest and
most abundant element in the universe.
• All matter inside the Sun is gravitationally attracted to all
the other matter in the Sun.
•This inward pull creates high pressures and temperatures
inside the Sun.
• The center is so violent and hot
that collisions between atoms break
the hydrogen atoms apart into their
subatomic ingredients.
Observing X-rays from
the sun.
•A hydrogen atom is made up of a proton, and a electron
that orbits the proton.
•In the Sun, collisions separate Hydrogen’s electron from
the proton, freeing each to move about the solar interior.
•A gas in which particles are ionized, or have electric
charges, is called plasma (the fourth state of matter).
• The separation of hydrogen nuclei from their electrons
makes nuclear fusion possible at the Sun's core,
producing the Sun's light and heat.
Hydrogen particles in
Helium out (mostly)
Nuclear Fusion in the Core
•With their electrons gone, hydrogen nuclei (protons) can be
packed much more tightly than complete atoms.
•At great depths inside the Sun, the pressure of overlying
material is enormous, the protons are squeezed tightly together,
and the material is very hot and densely concentrated.
•At the core, the temperature is 15,600,000oC
and the density is more
than 13 times that of solid lead.
•This is hot and dense enough to
achieve FUSION!
The nuclear fusion reaction that powers the Sun involves four protons
that fuse together to make one nucleus of helium. Two of the original
protons become neutrons.
The result is a helium nucleus, containing two protons and two
neutrons.
The helium nucleus has less mass, by 0.7 %, than the four protons that
combine to make it.
The fusion reaction turns the missing mass into energy, and this
energy powers the Sun.
The relationship between energy and
the missing matter was explained in
1905 by a German-born American
physicist Albert Einstein.
E = mc2
Energy equals mass times speed of light squared
.
The rate of nuclear reactions in the Sun is
relatively low, because protons repel each
other. Only a tiny fraction of the protons inside
the Sun are moving fast enough to overpower
this repulsive electrical force.
The nuclei that are moving fast enough can get
very close together, and strong nuclear force,
very powerful, but only over very short
distances. takes over, pulls the nuclei together
and holds them together.
In this way, nuclear reactions proceed at a
relatively slow pace inside the Sun. If the pace
were much quicker, the Sun would explode like
a giant hydrogen bomb.
http://library.thinkquest.org/C001124/gather/ssun.html
Spectroheliograph
image of the sun,
taken aboard
Skylab in 1973,
using the extreme
ultraviolet
radiation from
ionized helium,
304 Angstrom
wavelength.
The stages a star will go through and how long it will
last in each stage depends mainly on the mass
star mass (sol m.)
60
30
10
3
1.5
1
0.1
time (years)
Spectral type
3 million
O3
11 million
O7
32 million
B4
370 million A5
3 billion
F5
10 billion
G2 (Sun)
1000's billions M7
Color-enhanced Clementine
satellite image of the sunrise and
Venus over the moon.
http://www.astronomynotes.com/evolutn/s2.htm
What is the Sun made of?
Spectroscopy shows that hydrogen
makes up about 94% of the solar
material, helium makes up about
6% of the Sun, and all the other
elements make up just 0.13% (with oxygen, carbon, and nitrogen
the three most abundant ``metals''---they make up 0.11%).
In astronomy, any atom heavier than helium is called a ``metal''
atom. The Sun also has traces of neon, sodium, magnesium,
aluminum, silicon, phosphorus, sulfur, potassium, and iron. The
percentages quoted here are by the relative number of atoms. If you
use the percentage by mass, you find that hydrogen makes up
78.5% of the Sun's mass, helium 19.7%, oxygen 0.86%, carbon
0.4%, iron 0.14%, and the other elements are 0.54%.
How do we know? Spectroscopy!
For example, Helium was first discovered in the spectrum of the Sun
(the name helium derives from helios, which is the Greek name for
the Sun).
The spectral lines observed in the Solar emission spectrum could not
be associated with any known element and must belong to a new
element.
Helium was then discovered on the Earth (helium occurs in certain very
deep gas wells on the Earth)
and a new element was
confirmed.
Helium spectrum
Hydrogen Emission Spectrum
When an electric current is passed through a glass tube that contains hydrogen
gas at low pressure the tube gives off blue light.
When this light is passed through a prism, four narrow bands of bright light are
observed against a black background.
chemed.chem.purdue.edu/.../bp/ch6/bohr.html
So who figured this out?
•Not Dalton: His model of the atom assumed the atom to be an
indestructible mass, explaining most chemical reactions.
• The idea of indivisible atoms was shattered by Thomson and
Rutherford.
•Those guys who figured out there were
subatomic particles namely the electrons and
protons and a nucleus.
• Further Rutherford created an atomic model
of a positively charged nucleus surrounded
by electrons that explained some properties
JJ and Ernie talking about
of atoms, but not emission spectra.
old times
•Yet neither Rutherford nor Thomson’s models could explain why
the electrons of elements and compounds emit specific
wavelengths of light, rather than a complete spectrum.
For most of the 19th century, spectroscopists puzzled over these lines
for a wide variety of substances, with little to show for it.
Then a very perceptive Dane came on the scene. Modern atomic theory
begins with Niels Bohr (1885-1962). And his explanation for spectra.
Dr. Bohr, young and old
1. An energy level is the region around the nucleus where an
electron is likely to be moving.
2. According to Bohr, electrons cannot exist between the energy
levels – they have to jump from one level to another. To do this,
they must gain or lose a specific amount, or quantum of energy.
(losing emits light!)
• The term “quantum leap” comes from this idea.
Hydrogen atom and emission spectrum
http://outreach.atnf.csiro.au/education/senior/astrophysics/images/spectra/bohrhydrogen.gif
Spectroscopy
Emission Spectroscopy
Wavelengths and
intensity an excited
sample emits
Absorption spectroscopy
Wavelengths and intensity
of light passing through a
sample showing what the
sample absorbs
Sample A
Sample B
http://library.thinkquest.org/19662/images/eng/pages/model-bohr-3.jpg
http://www.astrocappella.com/background/doppler_background.shtml
•
MH is that of the most common variety of metal halide lamp, which is basically a
mercury vapor lamp enhanced with iodides of sodium and scandium.
•
High Pressure mercury vapor, typical of a mercury vapor lamp. Low pressure mercury
vapor has a similar spectrum except the green line is slightly dimmer and the yellow
lines are significantly dimmer.
•
Next one after that is a mercury lamp with the common Deluxe White phosphor.
CFL is compact fluorescent lamp of the 2700K color.