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

http://upload.wikimedia.org/wikipedia/commons/2/26/Plasma-lamp_2.jpg

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*

T is

https://apod.nasa.gov/apod/ap100418.html

• 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

APOD - Wisconsin

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 - Edmonton

Beautiful Aurora

APOD - Quebec

APOD - Finland

APOD - Missouri

APOD - Quebec

APOD - Quebec

APOD - Oklahoma

APOD - Washington

APOD – Alaska – Comet Ikea-Zhang

APOD - Norway

APOD - ISS

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