Lesson 5: Closer Look at the Sun, Nuclear Fusion in the Sun, Sun-Earth Connection Flashcards
Why does the sunshine? How do we know it’s not ‘on fire’ or due to ‘gravitational contraction’ ?
what is it powered by?
The Sun is powered by Nuclear Energy
E = mc^2
state the two types of equilibrium within the Sun (or any star for that matter)?
also Gravitational contraction
Gravitational equilibrium: Gravity pulling in which balances pressure pushing out
* The sun is the prefect equilibrium for gravity pushing down and pressure pushing out
Energy balance: Thermal energy released by fusion in core balances radiative energy lost from surface
Gravitational contraction: provided energy that heated the core as the Suns as forming. Contraction stopped when fusion started
How much larger is the Sun than Earth? How much more massive?
radius and mass that of Earth
Radius: 6.9×108 m (109 times Earth)
Mass: 2×1030 kg (300,000 Earths)
What is the Sun’s structure? Be able to describe the different layers of the Sun, where they are located in relation to each other, and their temperatures.
Solar wind: a flow of charged particles from the surface of the Sun
Corona: outermost layer of solar atmosphere; temperature of 1 million K; very not dense and spread out
Chromosphere: middle layer of solar atmosphere; temperature of ~10^4-10^5 K
Photosphere: visible surface of the Sun; temperature of ~6000 K
○ Includes sunspots
Convection zone: Energy transported upward by rising hot gas
Radiation zone: energy transported upward by photons
Core: energy generated by nuclear fusion; temperature ~15 million K
What are the two factors of Fusion?
Temperature and density
Describe the basic structure of an atom, what a hydrogen atom is
An atom is a fundamental a particle that contains electrons (negative), protons (positive), neutrons (neutral)
Hydrogen has a proton and an electron (no neutron)
What is a plasma? How is it different than a Gas?
Plasma: hot ionized gas
* stripped of one or more of their electrons — large quantity of free electrons and positively charged ions in the Sun, making it an electrically charged environment
Different from gas because:
Plasma is made up of groups of positively and negatively charged particles but particles of a gas are mostly uncharged.
Do protons attract each other or repel each other? Why?
Since charges of the same sign repel, protons mutually repel each other
What force keeps atomic nuclei together, instead of flying apart due to the repelling of all the protons?
The Strong Force holds Neutrons and Protons together
* But its limitation is far distance
At CLOSE distances (ie, within the nucleus), protons and neutrons attract
What is a Helium atom made of?
The helium atom:
2 neutron
2 proton
2 electron
What’s the difference between fission and fusion?
Fusion is the literal fusion of two particles together
○ Two or more protons coming together
Fission is the falling apart of atoms
Why is fusion between protons only possible at the centres of the Sun (or stars in general)?
High temperatures enable nuclear fusion to happen in the core
At high speeds, protons/nuclei can fuse together.. Not low speeds
What is the proton-proton chain? How does it create energy?
The proton-proton chain is how hydrogen fuses into helium in the Sun
* When two protons fuse together and make one proton, one neutron, one positron and neutrino
Overall reaction:
* IN: 4 protons
* OUT: 4He nucleus, 2 gamma rays, 2 positrons, 2 neutrinos
* **Total mass is 0.7% lower **
The resulting amount of material has turned into gamma rays
While we have never been to the centre of the Sun, Nuclear Fusion would explain a variety of things we observe about the Sun. What are those things we observe?
- Contains helium
- Emit a full spectrum of light (the gamma-rays that are produced at the core by fusion are reduced in strength as they random walk their way out to the surface)
- Will live for billions of years! (the time it would take to fuse all of the hydrogen would take billions of years)
discuss the Solar Thermostat theory.
Decline in core temperature causes fusion rate to drop, so core contracts and heats up
Rise in core temperature causes fusion rate to rise, so core expands and cools down
Energy is created in the centre of the Sun, describe the pathway the photons take as they leave the core and move through the radiation zone of the Sun. Describe the
path the photons take once they make it into the convection zone of the Sun.
- Gamma rays bounce off the plasma (protons and electrons) in the radiation zone for a million years
- Energy gradually leaks out of the radiation zone in the form of randomly bouncing photons
Then:
Convection layer
- Convection: rising hot gas takes energy to the surface
What is convection? How does it create the pattern we see on the photosphere of the Sun?
Convection (rising hot gas) takes energy to the surface)
- Bright blobs on photosphere where hot gas reaches the surface
Describe how we are able to know what is happening inside the Sun, specifically related to neutrinos.
Neutrinos created during fusion fly directly through the Sun (don’t react with anything)
* Observations of these solar neutrinos can tell us what’s happening in the core
so
provides direct evidence that nuclear fusion occurs in the sun and the Sun’s current status
What are Sunspots, Solar Flares, and Solar Prominences?
sunspots - also differential rotation
Sunspots: Are regions with strong magnetic fields
* Are cooler than other parts of the Sun’s surface (4000 K)
* Tracking sunspots has allowed us to measure the speed of rotation of the sun, which is not the same at all latitudes! This is called a Differential Rotation
Solar Flares: Magnetic activity causes solar flares that send bursts of x-rays and charged particles into space
* will travel through space
Solar Prominences: Magnetic activity also causes solar prominences that erupt high above the Sun’s surface
* the arch does not separate and go into space
Compare the Sun’s magnetic field to Earths.
Larger, stronger, more active, the Sun’s magnetic field changes over time, excites/heats particles
- The Sun is a plasma, which is a fluid. Plasma is a cloud of charged particles
- The Sun rotates with different rates depending on the latitude
Why doesn’t the Sun’s magnetic field act like a bar magnet? What does it end up acting like?
The sun’s magnetic field has two poles, like a bar magnet. The poles flip at the peak of the solar activity cycle, every 11 years.
- So, while the sun does have a magnetic field, with both a north and south pole like a bar magnet, it’s also very unlike a magnet and the Earth, because that magnetic field is complex, and changes dramatically over time
What are coronal mass ejections?
Coronal mass ejections: send bursts of energetic charged particles out through the solar system
How does the solar wind create aurora on Earth?
Auroras are the glow of the charged particles from solar winds which are interacting with Earth’s magnetic field and atmosphere (primarily near the poles, where Earth’s magnetic field is the strongest)
Why are sunspots dark?
They appear dark because they are cooler than other parts of the Sun’s surface
What is the solar cycle? What causes it? How do we know it’s occurring?
As well, define solar maxima and solar minima
Solar cycle: The Sun’s magnetic field goes through a cycle. Every 11 years or so, the Sun’s magnetic field completely flips.
* Sun’s north and south poles switch places
Caused by the the sun’s magnetic field
How do we know?
* In March of 1989, a geomagnetic storm caused a nine-hour outage of Hydro-Quebec’s electricity transmission system
- Heinrich Schwabe: Between 1826 and 1850 Schwabe kept daily records of the number of sunspots.
- Solar maxima (period when there is most sunspots; means the sun is more active) and solar minima (period when there is the least sunspots, means sun is less active)
- A drawing of the Sun made by Galileo Galilei on June 23, 1613 showing the positions and sizes of a number of sunspots. Galileo was one of the first to observe and document sunspots
Does the solar cycle have any measurable affect on Earth’s climate? How much does the Sun’s luminosity vary over the solar cycle?
It is unclear whether the sunspot cycle affects Earth’s climate in any way, but it almost certainly is not responsible for global warming
the luminosity of our Sun varies a measly **0.1% over the course of the 11- year-solar cycle. **
Does the Sun have a solid surface? What about its core?
The Sun does not have a solid surface or continents like Earth, nor does it have a solid core
What is the effective temperature of the Sun?
5800 K
What is the Sun’s atmosphere made of?
73% of the Sun’s mass is hydrogen, and 25% is helium.
* Other chemical elements are carbon, oxygen, and nitrogen, make up only 2%
(from the sun’s outer layers)
What is the definition of a plasma?
hot ionized gas
What are the layers of the Sun? Beginning from the core?
Core
Radiation
Convection
Photopshere
Chromosphere
Transition Region - temperature immediately rises
Corona
Why is the radiative zone named that? Why is the convection zone named that?
Radiative zone: region above the core, primary mode for transporting energy
- high density of matter region, means a photon cannot travel too far without encountering a particle, causing it to change direction and lose some energy
- extends up to about 70% of the way to the surface
Convective zone: outermost layer of the solar interior, transports energy from the edge of the radiative zone to the surface through giant convection cells
- the plasma at the bottom of the convective zone is extremely hot, and it bubbles to the surface where it loses its heat to space
What is the photosphere?
Photosphere: is the layer where the Sun becomes opaque and marks the boundary past which we cannot see
- Outside the Sun, we can observe only those photons (originally formed inside the Sun) that are emitted into the solar photosphere, where the density of atoms is sufficiently low and the photons can finally escape from the Sun without colliding with another atom
Over what distance does the Sun’s atmosphere change from completely transparent to completely opaque?
The Sun’s atmosphere changes from transparent to opaque over just a few hundred kilometers
- photosphere is about 500 kilometers thick
What is granulation? How does convection play a role in creating granulation?
Granulation: Observations with telescopes show that the photosphere (visible part) has a mottled appearance, resembling a pot of boiling oatmeal.
- The granular formation is due to the convective motion of the gas in the sub-photospheric layers, with the bright centre as upward flows and the dark lanes as downward flows
What is the chromosphere? What is the transition region?
What is the corona?
Chromosphere: region of the Sun’s atmosphere that lies immediately above the photosphere
Transition region: the part of the Sun where the rapid temperature rise occurs
Corona: The hottest part of the solar atmosphere, which has a temperature of a million degrees or more
What is the solar wind? What are aurora, and how are they generated?
Solar wind: Sun’s atmosphere is that it produces a stream of charged particles (mainly protons and electrons)
○ At the surface of Earth, we are protected to some degree from the solar wind by our atmosphere and Earth’s magnetic field. The magnetic field lines on Earth are at the north and south magnetic poles.
○ Here, charged particles accelerated by the solar wind can follow the field down into our atmosphere. As the particles strike molecules of air, they cause them to glow, producing beautiful curtains of light
Auroras: As the particles strike molecules of air, they cause them to glow, producing beautiful curtains of light
What is a sunspot? What are its two parts?
Sunspots: are large, dark features seen on the surface of the Sun caused by increased magnetic activity
They look darker because the spots are cooler
- Consists of two parts: an inner darker core, the umbra, and a surrounding less dark region, the penumbra
(like the moon in an eclipse)
What was Galileo able to do by tracking sunspots?
A drawing of the Sun made by Galileo Galilei on June 23, 1613 showing the positions and sizes of a number of sunspots. Galileo was one of the first to observe and document sunspots
What is differential rotation?
Differential rotation: the Sun rotates every 25 days at the equator and takes progressively longer to rotate at higher latitudes, up to 35 days at the poles
What is the sunspot cycle? How did we figure out it existed?
Sunspot cycle: the number of sunspots varied systematically, in cycles about a decade long
Heinrich Schwabe, a German pharmacist and amateur astronomer, kept daily records of the number of sunspots.
What is a sunspot minimum and sunspot maximum? How often do each occur?
- The beginning of a solar cycle is a solar minimum, or when the Sun has the least sunspots.
- Over time, solar activity—and the number of sunspots—increases. The middle of the solar cycle is the solar maximum, or when the Sun has the most sunspots.
Is the time between successive maxima/minima always the same?
what is the average?
sunspot maxima occur at an average interval of 11 years
- but the intervals between successive maxima have ranged from as short as 9 years to as long as 14 years.
Describe the Sun’s dynamo.
Dynamo: is a machine that converts kinetic energy (i.e., the energy of motion) into electricity.
○ is located in the convection zone
