Final Exam: Sun 3 Flashcards
What is the structure of the sun?
Diameter
Inner parts
Outer parts
Diameter = 100 times that of earth
Inner parts:
Core
Radiative zone
Convective zone
Outer parts:
Photosphere
Chromosphere
Corona
The sun is a typical star in terms of mass, size, surface temp., chemical composition
What is the suns energy source?
The sun closely approximates a blackbody with a surface temp. Of 5800 K
It emits radiation of all wavelengths with peak emission in the visible region of the EM spectrum
How do we know the suns surface temp.?
With wiens law
What is luminosity?
Luminosity is one of the basic properties used to characterize stars. Luminosity is defined as the total energy radiated by a star each second, at all wavelengths
Every second the sun produces an amount of energy equivalent to the detonation of 100 billion one -megaton nuclear bombs. Six seconds worth of solar energy output, suitably focused, would evaporate all of earths oceans. 3 mins. Would melt our planets crust
What is Solar Wind?
A flow of charged particles from the surface of the sun
What is the Corona?
The outermost layer of solar atmosphere
~1 million K
What is the Chromosphere?
Middle layer of solar atmosphere.
~ 10(4) - 10(5) K
() = the power to
What is the photosphere?
Visible surface of the sun
~6000 K
What is the Convection Zone?
Energy transported upward by rising hot gas
What is the radiation zone?
Energy transported upward by photons
What is the Core?
Energy generated by nuclear fusion
~15 million K
What are the suns layers? In order from outermost to innermost.
Solar winds Corona Chromosphere Photosphere Convection zone Radiation zone Core
Suns energy source
E=mc(2) - theory of relativity
M is mass and C is the speed of light in empty space
Thermonuclear Fusion: fusing together of 2 light nuclei to form a heavier nuclei
Nucleus 1 + nucleus 2 -> nucleus 3 + energy
Missing mass is converted to energy.
What is the atomic nucleus?
Positive protons on the nucleus would repel due to electrical force, but there is a stronger force that acts at this level (short range) and attracts “nucleons” — strong nuclear force.
When particles come together under strong nuclear force and unite to form nucleus - energy is released.
What is an isotope?
Same element and same number of protons and electrons but different number of neutrons.
Thermonuclear Fusion
It can take place only at extremely high temp. And pressure
Under these conditions atoms are completely ionized (stripped of all their electrons and only the nucleus remain)
These conditions are required for the positively charged nuclei to overcome the repulsive forces and fuse together
What is the proton-proton chain?
Hydrogen nuclei fuse together to form helium nuclei and in the process convert a small amount of mass into a large amount of energy
These reactions affect the nucleus of atoms - hence the name nuclear reaction
As opposed to
Chemical reactions that effect the electrons of atoms
How does thermonuclear reactions on the core of the sun produce its energy?
At extremely high temp. And pressure 4 hydrogen atoms can combine to make 1 helium atom and release energy to the process according to E=mc(2)
4H -> He + energy + v: hydrogen fusion
V= neutrinos: subatomic particles with no charge and little mass
Most energy released in thermonuclear fusion is in the form of gamma ray photons
Antimatter vs matter
Every particle has an antimatter counterpart:
Electron - antimatter is a positron
Same mass, opposite charge
What is hydrostatic equilibrium?
The sun has a very strong gravity, but does not collapse upon itself due to a balance of inward and outward pressures. This balance is called hydrostatic equilibrium.
- inward: gravity
- outward: pressure from being hot
• heated gases expand
What is gravitational equilibrium?
The outward push of pressure balances the inward pull of gravity
What is Solar Thermostat?
Decline in core temp. causes fusion rate to drop, so core contracts and heats up
Rise in core temp. causes fusion rate to rise, so core expands and cools down
What is thermal equilibrium?
At a given depth the temp. is constant
- it does not change with time
Since the sun is in thermal equilibrium, the. All the energy generated in the interior must be transported by some mechanism(s) to the surface, where it is emitted into space
There are 2 mechanisms by which energy is transported in the sun:
1) convection: circulation of gases (fluids) between hot and cold regions
- hot gases rise to the surface and the cooler gases sink to the interior
2) Radiative diffusion: photons created in the core diffuse outwards
- in and dear the core, the atoms are stripped of their electrons because of extremely high temp.
- they can’t capture photons. The deep interior is relatively transparent to radiation
- the result is a slow migration of the photons towards the surface.
What the inner parts of the sun do
Core?
Where energy is produced (thermonuclear fusion)
- temp. ~15 million K
- density ~ 160,000 kg/m(3) ~14 times as dense as lead
- pressure ~ 3.4 x 10(11) atm (1 atm = air pressure at sea level)
- suns energy is produced inside the region of 200,000 km (1/4 of the radius)
- outside this region the temp. is too low for thermonuclear fusion to take place
What the inner parts of the sun do?
Radiative zone
- this region is comparatively transparent to EM radiation
- energy is carried away from the core as electromagnetic radiation (photons) by the radiative diffusion mechanism
What the inner parts of the sun do?
Convective zone
In this region the temperature is low enough for nuclei to join with electrons and form hydrogen atoms, and these absorb light very efficiently
- gases are opaque to light, this convection is the transparent mechanism
What are the methods of probing the interior of the sun?
Helioseismology
HELIOSEISMOLOGY: measuring vibrations of the sun as a whole
- the sun will vibrate at a variety of frequencies like a ringing bell
- these vibrations can be observed at the surface
- studying these vibrations give scientists valuable information about the suns interior
What are the methods of probing the interior of the sun?
Solar neutrinos
They are the only direct evidence of the thermonuclear reaction at the core
- only the neutrino v survives the journey through the solar interior
- the v has energy but no charge and ALMOST no mass
- travels almost at the speed of light and interacts with nothing: goes right through the earth
- with knowledge of neutrinos physics scientists have built neutrino detectors to study these particles
The outer parts of the sun
Photosphere - surface of sun that we see. radiates energy as continuous spectrum (5800 K)
Lowest of the 3 layers
All visible lights we see from this layer
Low density gas, primarily hydrogen and helium
We know this by absorption lines
Chromosphere - pow density gases form “atmosphere” red colour comes from hydrogen emission line
Corona - outer part of atmosphere, extremely hot
What are sunspots?
Sunspots occur in pairs; the pairs cluster into groups; and they rotate with the sun
- typically of earth size
- they are not permanent, lasting anywhere between a few hours to a few months
- sunspots occur over an 11 year cycle
How long does the sun experience a solar cycle
11 years, same as sun spots
Solar activity
All these activities seem to follow the 11 year cycle
When solar flares and coronal mass ejections are aimed towards earth
- a stream of high energy electrons and nuclei reaches us a few days later
- these interfere with satellites
- poses a health hazard to astronomers in orbit
- disrupt electronics and communication equipment
- Aurorae
