Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation...
-
date post
15-Jan-2016 -
Category
Documents
-
view
220 -
download
0
Transcript of Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation...
![Page 1: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/1.jpg)
Introduction to Astronomy
• Announcements
![Page 2: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/2.jpg)
The Sun, Our StarThe Sun, Our Star
Size & Structure
Energy Generation
Magnetic Activity
The Solar Cycle
![Page 3: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/3.jpg)
Size & StructureSize & Structure
Basic properties of the Sun…
![Page 4: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/4.jpg)
• DSun ~ 100 Dearth
– A million Earths could fit inside the Sun
• MSun ~ 300,000 MEarth
– I weigh 225 lbs on Earth.– On the Sun, I would weigh ~ 3 tons!
• Distance to Earth = 150 million km = 93 million miles = 1 AU– Driving at 75 miles/hour, you would reach the
Sun in 141½ years!
![Page 5: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/5.jpg)
![Page 6: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/6.jpg)
• Surface Temperature ~ 6000 K– Measured from color & Wien’s Law
• Core Temperature ~ 15 million K ~ 27 million °F– from modeling/calculations & indirect
measurements
![Page 7: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/7.jpg)
![Page 8: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/8.jpg)
• Composition– 71% Hydrogen– 27% Helium– 2% vaporized heavy elements
• Oxygen, Silicon, Calcium, Iron, Strontium, Titanium, etc…
• Radiant Energy ~ 4 x 1026 Watts– Compare this to your 60 Watt household light
bulbs
![Page 9: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/9.jpg)
Solar Structure
• Photosphere (top-most, only directly visible layer)
• Convective Zone (pot of boiling water)
• Radiative Zone (direct energy radiation)
• Core (powerhouse)
![Page 10: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/10.jpg)
![Page 11: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/11.jpg)
Core
• Fusion here to produce energy
• More on this in a minute…
![Page 12: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/12.jpg)
![Page 13: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/13.jpg)
Radiative Zone
• Energy (photons of light) produced in core must travel outward
• In this zone, energy moved by direct radiation– Campfire analogy: energy from fire travels
outward by RADIATION
• You can feel the heat from the fire w/o putting your hands directly into the flames
![Page 14: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/14.jpg)
• Incredibly dense, so photons can travel only ~ 1 inch before they are absorbed by atoms in the gas– Re-radiated, but then can only travel another
inch before re-absorbed• “Random Walk”
– Photons re-radiated in random directions
• These photons take an average of 16 million years to reach the surface!
““Today’s sunshine was born in the Sun’s core before we even existed as Today’s sunshine was born in the Sun’s core before we even existed as a species!”a species!”
![Page 15: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/15.jpg)
The distance traveledis much greater thanthe net displacement
![Page 16: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/16.jpg)
![Page 17: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/17.jpg)
Convective Zone
• Further from core, so gas is much cooler…
– Lower temps mean gas atoms can “hang on” to more of their electrons
– This causes much more absorption at the base
– Therefore, heat piles up at the base, starts the gas “boiling”
![Page 18: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/18.jpg)
Photosphere
Convective Zone
Radiative Zone
Core
Not to scale
![Page 19: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/19.jpg)
• “convective currents”– Hot gas near base is less dense, so it starts to
float to surface– Gets to surface, cools down, becomes more
dense, sinks back below– Continue ad infinitum…
• Granulation– Convection cells– Move at ~ 1 km/sec
Cooler here
Hotter here
![Page 20: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/20.jpg)
![Page 21: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/21.jpg)
Photosphere
• Name = “light sphere” (visible surface)• Has density similar to liquid water• Below this surface, gas density increases rapidly
– The Sun is gaseous throughout
– No solid core• Temperatures too high to form molecular bonds required to
have solids and/or liquids• Despite incredibly huge densities
![Page 22: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/22.jpg)
![Page 23: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/23.jpg)
• Solar atmosphere– Everything above the visible surface
(photosphere)– Very low density gases
– Chromosphere– Corona
![Page 24: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/24.jpg)
![Page 25: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/25.jpg)
Chromosphere
• Thin layer
• Typical temperature ~ 25,000 K
• Name = “color sphere”– Most emission is red light from Hydrogen
• Spicules– Vertical jets of hot gas– Formed from shock waves rising through
photosphere (from convection)
![Page 26: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/26.jpg)
![Page 27: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/27.jpg)
![Page 28: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/28.jpg)
Mostly vertical…
Due to many overlappingspherical shock waves
![Page 29: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/29.jpg)
Corona
• Typical temperature 1 – 10 million K
• Such low density, we look right through it without noticing it– Only visible during solar eclipse – Or with special coronagraphic telescopes
• Coronal Streamers (X-Ray)
• Coronal Holes (source of solar wind)
![Page 30: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/30.jpg)
chromosphereStreamers
Corona in visiblelight
![Page 31: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/31.jpg)
Coronal Holes
Corona in X-Rays
![Page 32: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/32.jpg)
Energy GenerationEnergy Generation
What makes the Sun shine? How?
![Page 33: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/33.jpg)
• Hydrostatic Equilibrium
– Outward pressure balances inward force of gravity
– Ex: tire pressure• Air pressure in tire balances weight of car• Let air out = no pressure = flat tire = weight of car
not balanced = car sinks down
– Ex: floating• Buoyancy forces balance your weight in pool
![Page 34: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/34.jpg)
![Page 35: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/35.jpg)
• In a gas:– Pressure increase comes from squeezing
atoms closer together...(density increase)
– …or making them move faster…(temperature increase)
![Page 36: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/36.jpg)
• Increase density– More atoms in a given volume = more
frequent collisions
• Increase temperature– Atoms move faster = harder, more frequent
collisions
• Therefore, PRESSURE = DENSITY x TEMPERATURE x A CONSTANT
![Page 37: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/37.jpg)
![Page 38: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/38.jpg)
• So to balance Sun’s enormous gravity, need high densities and high temperatures in the interior…
![Page 39: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/39.jpg)
Powering the Sun
• Early theories1. Sun made of coal
• if true, Sun would only shine for few thousand years
2. Sun NOT in H.E., but gravitationally compressing & heating gases
• If true, Sun would only shine for 10 million years• If true, Sun would be shrinking enough to observe
over the last 100 years or so…
![Page 40: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/40.jpg)
• Bogus.
• New theory (late 1920s – early 1930s)
– Nuclear fusion in Sun’s core (heavy elements could be forged by smashing light elements together)
– E = mc2
• 1 gram of matter “contains” energy equal to that released by small nuclear device!
![Page 41: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/41.jpg)
• In Sun’s core, have incredibly high temperatures– Atoms move incredibly fast
– Normally, 2 protons moving toward each other would repel
• Recall opposite charges attract, like charges repel
– But, if moving fast enough, protons (nuclei) are driven extremely close together
• Strong force overcomes electrical repulsion• Protons bound together to form heavy nucleus
![Page 42: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/42.jpg)
“Collision” of like-charged particles
![Page 43: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/43.jpg)
• Proton-Proton Chain (PP Chain)
– 11HH + 11HH 22HH + e+ + neutrino + extra energyextra energy– 11HH + 22HH 33HeHe + photon + extra energyextra energy– 33HeHe + 33HeHe 44HeHe + 11HH + 11HH + extra energyextra energy
– Note that a little bit of energy is liberated at each step of this process…
– Note also that the final step regenerates the reactants needed for the initial step!
![Page 44: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/44.jpg)
![Page 45: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/45.jpg)
![Page 46: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/46.jpg)
![Page 47: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/47.jpg)
• 4 protons (1H) needed to produce each 4He
• Mass difference:
– 4 x mass of proton > mass of 4He
– “extra” mass converted to extra energy (E=mc2)
![Page 48: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/48.jpg)
• 0.048 x 10-27 kg = 4.3 x 10-12 J of energy– Pretty small, but…– ~ 30 MeV (1/40 eV = room temperature)
• Many, many, many of these reactions happen every second!– Total rate equivalent to 100 billion 1-megaton
nuclear devices exploding per second!– Hiroshima Bomb ~ 15 kilotons = 0.015
megatons
![Page 49: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/49.jpg)
• The PP-Chain is the dominant fusion reaction in stars that are roughly the same size/age as our sun…
• Other reactions are possible (triple-α process, CNO-cycle)– These occur mostly in heavier, older stars
![Page 50: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/50.jpg)
Introduction to Astronomy
• Announcements– HW #5 due monday
![Page 51: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/51.jpg)
The Sun’s Core
• Two “experiments” allow us to figure out what’s going on in the core
– Neutrino observation
– Helioseismology
![Page 52: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/52.jpg)
Neutrinos
• Generated in PP chain– “counting” them gives info about the rate of
fusion in the core• Counting is difficult: neutrinos have NO electric
charge and a vanishingly small mass• VERY weakly-interacting
• Recall photons take ~ 16 million years to reach surface
– Neutrinos take ~ 2 seconds!
![Page 53: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/53.jpg)
• ~ 1 trillion solar neutrinos pass through your body every second!
– Could pass through a light-year of lead without “hitting” a single atom!
– So how do we detect them, if they don’t interact?
– Can only detect a very small fraction
![Page 54: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/54.jpg)
• Neutrino detectors– Huge containers of “HEAVY WATER”
• D2O: each Hydrogen atom in H2O also contains a neutron
– Containers buried deep below mountains to filter out cosmic rays & other high-energy particles
• “outer space” particles• Constantly raining down on Earth
– In fact, may be cause of lightning
![Page 55: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/55.jpg)
• When neutrinos interact with a neutron in the heavy water, it changes the neutron into a proton and an electron– the electron zooms off, passing through the
heavy water– When it does, it emits a faint flash of light
(Cerenkov radiation)– Tank of heavy water lined with photodetectors
that can detect this flash.– VERY RARE: only expect one or two flashes
per year!
![Page 56: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/56.jpg)
Sudbury NeutrinoDetector
Located about 1.5miles undergroundnear Sudbury,Ontario, Canada
Contains 1000 tonsof heavy water in~ 20 foot sphere
![Page 57: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/57.jpg)
Helioseismology
• Just like earthquake seismic waves gives info on Earth’s interior
• Looking at the sound waves produced by the solar convective zone gives info on density & temperature of solar interior
– Analogy: hearing further on a cold day• Low temps mean slow atom motion means
pressure waves travel farther before they die out
![Page 58: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/58.jpg)
• As the sound waves travel throughout the Sun, they venture into regions with different temperatures, pressures, and densities
• This changes their speeds, and hence the ways in which they overlap…
![Page 59: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/59.jpg)
Vibration patterns onthe Sun…
Red = surface movingoutward
Blue = surface movingInward
Gray = nodal lines(no movement)
![Page 60: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/60.jpg)
• The true vibration pattern is a superposition of many different vibrations
![Page 61: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/61.jpg)
Magnetic ActivityMagnetic Activity
The most interesting phenomena on the Sun!
![Page 62: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/62.jpg)
Tutorial: Magnetic Fields• Ferromagnetism
– Most familiar…kitchen magnets, compass needles
• Induced magnetism– Produced by moving
charges– Current-carrying wire
deflects compass needle
• Currents create magnetic fields
![Page 63: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/63.jpg)
• A field is just an easy way of describing the effects of long-range forces– i.e. the forces that drive the pistons in an
engine are mechanical and thermodynamic in nature
• Require contact between the various components
– Gravity is a long-range force• “gravitational field”• Interaction between two massive bodies that are
not necessarily in contact
![Page 64: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/64.jpg)
• Similarly, the magnetic field describes the interaction of charges (protons, electrons, ions) that are not necessarily in contact
• A bar magnet produces a magnetic field at every point in space– Charges interact with the bar magnet by the
forces that the field exerts on them
![Page 65: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/65.jpg)
Sunspots
• Large, dark areas in the photosphere– Typically >> the size of the Earth!– Dark because they are cooler than
surrounding areas (3000-4000K)– Regions of STRONG magnetic fields
• Charged particles (p+ & e-) are forced to spiral around field lines
– Therefore, heat is rising more slowly than in the surrounding areas
– So appears cooler…
![Page 66: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/66.jpg)
Meanwhile, particles outside the magnetic field can zoom straight up and out, much faster than those spiraling around the field lines…
…therefore, they transport heat faster, and areas outside sunspots are much brighter
![Page 67: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/67.jpg)
Umbra
Penumbra
![Page 68: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/68.jpg)
Subsurface magnetic fieldlines organized in “bundles” called flux tubes, held together by gas pressure pushing in on them…
Above surface (photosphere), fieldlines spread out due to drop in gas pressure
Umbra
Penumbra
![Page 69: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/69.jpg)
![Page 70: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/70.jpg)
Visible(“white-light”)
Calciumemission
![Page 71: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/71.jpg)
![Page 72: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/72.jpg)
So how do we know that Sunspots are related to magnetic fields?
![Page 73: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/73.jpg)
The Zeeman Effect
In the presence ofa magnetic field,absorption linessplit into multipledistinct lines
Yet anotherpiece of informationthat an object’s spectrum tells us.
![Page 74: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/74.jpg)
The magnetic fields in and around sunspots act like north and south poles…
![Page 75: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/75.jpg)
X-ray image of “coronal loops”
Sunspots here
![Page 76: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/76.jpg)
Prominences & Flares
• Prominences– Reduced heat flow to a small region inside
flux tubes cools the gas there• Therefore, the pressure is smaller than outside this
region• Gas is well-confined by this high-pressure “bottle”
– gas can flow through, sometimes rising into the corona, sometimes raining down to photosphere
![Page 77: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/77.jpg)
![Page 78: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/78.jpg)
• Flares– Brief, bright eruptions of hot gas, usually at or
near sunspots• VERY bright in X-rays, UV• Not so bright in visible radiation (generally)
– Caused by twisting motions of sunspots?• KINK INSTABILITY
– Highly twisted magnetic fields violently re-adjust themselves into a new, lower-energy configuration
– Drastically heats surrounding gases in the process
![Page 79: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/79.jpg)
CCD bakeout(like over-exposingfilm)
![Page 80: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/80.jpg)
“Halo” flare: “it’s coming right for us!”
Flaring prominence
Magnetic (“arcade”) loopsseen edge-on
![Page 81: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/81.jpg)
Notice all the different orientationsof the loops…this weaves what wecall the “magnetic carpet” of the Sun
![Page 82: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/82.jpg)
![Page 83: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/83.jpg)
![Page 84: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/84.jpg)
![Page 85: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/85.jpg)
![Page 86: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/86.jpg)
![Page 87: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/87.jpg)
• Solar Wind– Steady mass loss due to high temperatures in
corona• Protons & electrons move fast enough to escape
Sun’s gravity– Recall atom speed depends on temperature
• Travel outward into solar system
![Page 88: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/88.jpg)
The Parker Spiral
![Page 89: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/89.jpg)
![Page 90: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/90.jpg)
![Page 91: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/91.jpg)
![Page 92: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/92.jpg)
The Solar CycleThe Solar Cycle
Periodic changes in the Sun’s magnetic activity
![Page 93: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/93.jpg)
About 6 years between opposite ends of this full-disc X-ray montage
Solar Maximum
Solar Minimum
![Page 94: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/94.jpg)
• Number of sunspots & frequency of flares changes over an interval of ~ 11 years
• Cause is hotly-debated– Main theory is “α-Ω Dynamo”– Combination of Sun’s rotation and the
convection in the convective zone
![Page 95: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/95.jpg)
Amplitude (max. number of sunspots) is wildly variable, butperiod (# years between successive peaks/troughs) is very
steady (~ 11 years)
![Page 96: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/96.jpg)
• Differential Rotation (“The Ω Effect”)
– Sun rotates faster at equator, slower at poles
– Magnetic fields are “stretched” along direction of rotation
– Makes magnetic fields stronger (like stretching a rubber band increases its tension)
![Page 97: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/97.jpg)
Differential Rotation
![Page 98: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/98.jpg)
![Page 99: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/99.jpg)
• Convection (“The α Effect”)– When magnetic field is strong enough, the
gas it contains becomes buoyant (starts to float)
– Convection then drags it up toward surface– SUNSPOT PAIRS
• Whole process still not well-understood– Helioseismology can’t probe ALL the way
down, so lack of data
![Page 100: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/100.jpg)
![Page 101: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/101.jpg)
![Page 102: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/102.jpg)
![Page 103: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/103.jpg)
northsouth
![Page 104: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/104.jpg)
![Page 105: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/105.jpg)
Sunspot Rules
• Joy’s Law– Tilt of bipolar
sunspot pairs
![Page 106: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/106.jpg)
• Hale’s Law– Sunspot polarity reversal
Hemispheric rule:Hemispheric rule:
If N magnetic pole leadsin Northern Hemisphere,then S magnetic pole leadsin Southern Hemisphere
![Page 107: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/107.jpg)
Reversal rule:Reversal rule:Leading polarities reverse from one solar cycle to the next…
![Page 108: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/108.jpg)
Links Between Sun & Earth Climate
• Sun heats corona
• Corona drives solar wind
• Solar wind alters Earth’s upper atmosphere
• Jet streams may shift (not conclusive)– May alter rainfall and storm patterns
![Page 109: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/109.jpg)
![Page 110: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/110.jpg)
• Maunder Minimum– 70 year period of little or no sunspots– Corresponds to ~ 70 year period of
abnormally-cold winters in Europe, rapid glacier advances, longer periods of frozen-over rivers
• “Little Ice Age”
![Page 111: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/111.jpg)
A couple more movies to tie it all together…
Zoom-in on the Sun
Hinode Ca II Sunspot & Two-ribbon Flare
![Page 112: Introduction to Astronomy Announcements. The Sun, Our Star Size & Structure Energy Generation Magnetic Activity The Solar Cycle.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649d5d5503460f94a3c098/html5/thumbnails/112.jpg)
NEXT TIMENEXT TIME
• Measuring the Properties of Stars