Study Points• Our sun is a star, one of billions of other stars.
• Why does our star look so much bigger than other stars?
• Is it bigger than other stars?
• How many Earths can fit across the diameter of our sun?
• What state of matter is our sun?
• Describe how the Sun’s “surface” and the Earth rotate differently?
• What is the composition of our sun? What percent by counting? What
percent by weight?
• What is the corona? What is the photosphere?
• What is a sunspot? Discuss the sunspot cycle.
• What is a solar flare? A solar prominence? A coronal mass ejection (CME)?
• What are some of the consequences of CMEs?
• What powers the Sun and other stars? Describe the process.
• What is the solar wind?
• Explain what you are seeing when you see aurora?
Sun• A few traits of our sun
• Fusion: What powers our sun
• Aurora
The Sun in the News
• NASA’s Parker Solar Probe
– 7 year mission to study our Sun
– Goal to Answer: Why is the corona hotter than
the surface? Why is there a solar wind?
– Launched August 12, 2018
– Fastest spacecraft ever
– Closest to Sun
• Read more here:
http://parkersolarprobe.jhuapl.edu/
Sun
A star like billions of other starshttp://antwrp.gsfc.nasa.gov/apod/ap100817.html
Sun
Why does Sun look bigger than other stars?*http://antwrp.gsfc.nasa.gov/apod/ap100817.html
It is close.*
Sun Discussion Questions
1. How many Earth’s fit across the Sun’s
diameter?
2. What 2 elements make up most of the Sun?
3. How hot is the sun’s “surface”?
4. Which part of the sun is the hottest:
“surface” or surrounding gas cloud?
Sun Discussion Questions
1. How many Earth’s fit across the Sun’s
diameter?
2. What 2 elements make up most of the Sun?
3. How hot is the sun’s “surface”?
4. Which part of the sun is the hottest:
“surface” or surrounding gas cloud?
~100
Hydrogen & Helium
~9000oF
Surrounding gas cloud
called the corona
How Big is the Sun?
Sun – Average Star* (know the sun is average size, but don’t need to know numbers)*
Diameter of Sun
= 1.4 x 106 km = 1.4 million km
(900,000 miles)
Largest Star Diameter
~= 1400 to 2600 times the size
of Sun (maybe not more than
1500 times)
http://learn.arc.nasa.gov/planets/0/
~100 Earths fit
across the
diameter
of the Sun*
Diameter of Earth
= 13,000 km (8000 miles)
Recall scaling:
cardboard sun & pushpin
Sun – A Plasma*
Hot, ionized gas
Solid, liquid, gas, plasma
Copyright1994 General Atomics
Examples of Plasmas
• Plasma ball
• Rocket exhaust
• Flames (1500F+)
• Lightning
• Sun
Does the Sun Rotate?
Surface Rotation
• Earth rotates
• Sun also rotates
– Watch 2nd video:
https://svs.gsfc.nasa.gov/4246
Surface RotationBecause the Sun
is a plasma,
the equator
rotates faster
than the poles
(north and
south).*
On Earth, the surface
rotates at the
same rate.*
https://www.nasa.gov/mission_pages/sune
arth/science/solar-rotation.html
How much does the Sun weigh?
What is the Sun’s mass?
Sun – General Information
Sun’s Mass
~1030 kg (~million Earths, know this)
(Earth is ~6x1024kg or 13x1025lbs)
→Most mass of solar system (99.8%)*
Mass of Sun
= 2 x 1030 kg (4 x 1030 lbs)
Largest Star Mass
~= up to 265 times the
mass of Sun (maybe not
more than 150 times)
How hot is the Sun?
Sun – General Information
https://www.nasa.gov/mission_pages/iris/m
ultimedia/layerzoo.html
Sun’s Temperature• Photosphere (Sun’s “surface”):
– ~5000 K (~9,000o F)
• Core (inside Sun): – ~15,000,000 K (~27,000,000o F)
• Chromosphere (Sun’s atmosphere):
– ~6500 K (~11,000o F)
• Corona (outer layer):
– ~500,000 K (~900,000o F)
What is the Sun’s composition?
Sun – General Information
Sun’s CompositionCecilia Payne (1920’s)
- Stars are hydrogen (H) & helium (He)*
~90% H, ~10% He
(9 atoms of H to 1 atom of He)
a few other elements like C, Si, Fe
Note: Sometimes you hear 75%:25%
Counting vs weighing…
Sun – General Information
Sun’s Composition*Counting: ~90% H, ~10% He (9 H to 1 He)*
*By mass: ~75% H, ~25% He *
(Learn these)
Looking at the Sun
"Copyright Association of Universities for
Research in Astronomy Inc. (AURA), all
rights reserved." "National Optical
Astronomy Observatories, National Science
Foundation"
Solar Terminology
Photosphere*
Visible surface of the Sun*
Corona*
http://science.nasa.gov/newhome/headlines/images/eclipse/beautifulcorona_big.jpg
Hot gas
around the
Sun*
• Dark “storm”
• On photosphere (surface)
• Cooler than surrounding area (darker)
• Concentration/change of magnetic field
• Summary: cooler magnetic storm on Sun’s surface*
"Copyright Association of Universities for
Research in Astronomy Inc. (AURA), all
rights reserved." "National Optical
Astronomy Observatories, National Science
Foundation"
Sunspot*
"Copyright Association of Universities for
Research in Astronomy Inc. (AURA), all
rights reserved." "National Optical
Astronomy Observatories, National Science
Foundation"
Today’s sunspots
Watch/View:
http://sohowww.nascom.nasa.gov/
Sunspot Cycle*
http://www.swpc.noaa.gov/products/solar-cycle-progression
https://solarscience.msfc.nasa.gov/images/Cycle22Cycle23Cycle24big.gif
https://solarscience.msfc.nasa.gov/SunspotCycle.shtml
~11 year cycle*
Numbers of sunspots vary
Solar minimum
Solar maximum
View/Watch current solar cycle at:
• Loop of hot gas & plasma
above the sun’s surface*
• Hangs in the corona, still connected to Sun
• Lasts hours to days*
• Supported by magnetic field
• Bright when seen on the sun’s edge
• Watch/Play eit solar rotation
• Or watch the first video from:
https://svs.gsfc.nasa.gov/4246
Prominence*
• Rapid release of energy*
– Seconds long*
• From a localized region
• Energy from magnetic field is suddenly
released
• Made of EM radiation, energetic particles
– EM Spectrum includes radio, microwave,
infrared, visible, ultraviolet, x-rays, gamma
rays; light particles at different wavelengths
Solar Flare*
Coronal Mass Ejection (CME)*
Watch:
http://sohowww.nascom.nasa.gov/gallery/Movies/flares.html
(go to “Amazing CME” - blue)
(go to “Several CMEs and one proton storm” - red)
• Large ejection of EM radiation and
charged particles*
• Lasts hours to days
• Typically a break of a prominence
• Big area of Sun
What is the Difference Between a CME &
Solar Flare?
Difference Between a CME & Solar Flare
- Solar Flare
- smaller, localized region, shorter (seconds)
- CME
- larger, big region of the Sun, longer (days)
You can read more here:
http://cse.ssl.berkeley.edu/coronalweather/CMEsFlares/
Coronal Mass Ejection –
Problems for Earth and Earthlings*http://hesperia.gsfc.nasa.gov/sftheory/spaceweather.htm
• Blocks Communications – Radio, TV, Cell phones, Over-the-Horizon radar, air traffic control radio frequencies
• Navigation Systems (LORAN, GPS) – degrades orbit
• Satellites affected by CME– Heats atmosphere & expands it, changing satellite orbits
– Electronics fried by energetic particles
• Radiation Hazards to Humans – astronauts on ISS or going to Moon or Mars, airplane crews and passengers (small)
• Electric Power grids – ex: 1989 blackout in Canada, 1859 Carrington Event (extremely bright auroras)
• Global Climate affected by solar cycle maximum & minimum– Link between solar minimum and “the little ice age” 1500 to 1850
• Biology – ex: homing pigeons, blind moles, dolphins?, whales? – use Earth’s magnetic field to guide them
https://science.nasa.gov/science-news/science-at-nasa/2014/23jul_superstorm
Star Power
How Fusion Powers the Sun
•Gravity pulls in
•Energy from fusion
pushes out
Balance -Hydrostatic Equilibrium
Stars with Forces in Balance
• Mash light elements together to form
heavier elements*
• Form heavier elements + release energy
EX: 4H → 1He + 2e+ + 2e + energy
more mass → less mass
E = mc2
The sun is giving off mass and losing gravity.
Fusion will make the Sun larger over a long time period.
Fusion – Powers the Sun/Stars*
Fun fact: The sun loses mass,
about 4 million tons every second!
Sun-like stars:
H → He… (Li, Be, B)… C
Fusion
Fusion Summary
• Gravity pulls in, energy from fusion pushes out
• Star is balanced
• Fusion: lighter elements → heavier elements + energy
• E = mc2
• Sun like stars produce He…C
Aurora Borealis
(Northern Lights)
Aurora Australis
(Southern Lights)
APOD - Wisconsin
What causes the aurora?
Solar Wind – causes aurora*
• Continuous flow of particles from Sun
- Protons, electrons, ions
http://learn.arc.nasa.gov/planets/0/
Solar windEarth’s
magnetic
field
Solar Wind – causes aurora*
Solar windEarth’s
magnetic
field
Charged
particles
spiral
toward
poles
Solar Wind – causes aurora*
Solar windEarth’s
magnetic
field
Charged
particles
spiral
toward
poles
Charges
interact
with Earth’s
atmosphere
Solar Wind – causes aurora*
Solar wind
Charged
particles
spiral
toward
poles
Energy
released
Charges
interact with
Earth’s
atmosphere
Earth’s
magnetic
field
Solar Wind – causes aurora*
http://mms.gsfc.nasa.gov/
Magnetospheric Multiscale
Mission (MMS Spacecraft)• 4 satellites studying how the
magnetic fields of the Sun and Earth
interact because of the material
coming off the Sun
• Launched March 12, 2015
• http://mms.gsfc.nasa.gov/
CRT and Magnet
Watch: https://www.youtube.com/watch?v=YbzBTdU7iRU
APOD - Washington
APOD – Alaska – Comet Ikea-Zhang
Aurora from the International
Space StationWatch:
https://www.youtube.com/watch?v=FG0fTKAqZ5g
Aurora on Other Planets
http://antwrp.gsfc.nasa.gov/apod/ap011114.html
short motion clip
Space Weather Prediction Center
Watch/View: http://www.swpc.noaa.gov/
• Watch: http://apod.nasa.gov/apod/ap101124.html
• Or http://vimeo.com/16917950 (2:42)
Homework & Updates• Video to view at home about the Sun:
https://www.nasa.gov/mission_pages/sunearth/news/solarcycle-primer.html
• Lab Update – 2 labs left; come to lab as normal next week• Lab Quiz on Dimensional Analysis & Significant Figures, open
notebook, 10 points
• Doppler Lab this week, come prepared, 8 points
• Observations:• Astrophysics Lecture Due Dec. 3 (10 pts) Write report (Lecture done 10/10)• Astronomy News Evalution Due Dec. 10 (20 pts) Evaluate astronomy news• Planetarium Due Dec. 3 (10 pts) Go to a planetarium show (Field trip 10/3)• Stargazing Due Dec. 17 (20 pts) Go stargazing & write report• Telescope Due Dec. 17 (20 pts) Look through a telescope• Moon Craters Due Dec. 17 (10 pts) Look at magnified moon craters
• Borrow binoculars from Lab room
• Test 2 Results on Thursday
Video to view at home about
the Sun: https://www.nasa.gov/mission_pages
/sunearth/news/solarcycle-
primer.html