Class Update• Observations• Friday, Mar. 20

• 8-9:30pm University of Minnesota (Telescopes & Star Gazing, NO MOON) PRINT VERIFICATION SHEET from calendar

• Test 2 on Tuesday, March 24 (in 1 week)• 40 multiple choice questions• 20 points possible for Mars/Saturn Writing Assignment (see

calendar for more details)• Need to type/print and have it ready at the beginning of

the test• Test covers material from Feb. 12 to Mar. 19 • Study Session with Gus: Thur, Mar. 19 3-5pm Room S3500• Studying

• 1. D2L Quizzes 5, 6, 7, 8 (10+ questions on test)• 2. Review Lecture Objectives (file on Mar. 24 on calendar)

Class Update

• Science Museum of Minnesota “Space: An Out of Gravity Experience” FREE!• Thursday, May 7 5:30pm to 8:30pm (museum open until 9pm)

• Reserve the date on your calendar

• 6pm Journey to Space Omnitheater movie• 7pm entrance to Space exhibit• http://www.smm.org/space• Parking $5 between Exchange and Eagle ($9-$12 at museum)• Parking location: http://tinyurl.com/mdw8ush• Meet Raquel in lobby at 5:30pm• RSVP required (email notice coming soon)• FREE for astronomy students; other family or friends are $19/person

(normal price is $31/person)

Sun• A few traits of our sun• Fusion: What powers our sun• Aurora

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.

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 across the diameter of the Sun (know this for test)

Diameter of Earth

= 13 000 km (8000 miles)

Recall scaling:

beach ball / BB

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

Why Does the Sun Really Shine?

Does the Sun Rotate?

Surface Rotation

• Earth rotates (See globe)• Sun also rotates – play video

(See windows2 universe)

Surface Rotation

But Sun is a plasma.

Equatorial zone rotates faster than zones north and south.

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%) (know this)

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

Sun’s TemperatureSurface: ~5800 K

(~10 000o F)

http://www.a2gov.org/government/safetyservices/emergencymanagement/planning/Pages/HeatWave.aspx...

Sun’s TSurface: ~5800 K

(~10 000o F)

Core: ~15 000 000 K (~27 000 000o F)

What is the Sun’s composition?

Sun – General Information

Sun’s CompositionCecilia Payne (1920’s)

~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 CompositionCounting: ~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

PhotosphereVisible 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• Cooler than surrounding area• Concentration of magnetic field

"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 sunspotshttp://sohowww.nascom.nasa.gov/

Sunspot Cycle

~11 year cycle

Numbers of sunspots vary

Solar minimum

Solar maximum

Current solar cycle at:

http://www.swpc.noaa.gov/products/solar-cycle-progression

• Relatively cool, dense

cloud of gas/plasma

• Hangs in the corona, still connected to Sun• Lasts days to weeks • Supported by magnetic fields• Bright when seen on the sun’s edge• Play eit solar rotation

Prominence

• Rapid release of energy – Seconds long

• From a localized region • Made of EM radiation, energetic particles

– EM = electromagnetic; this will be covered more in future lectures

– EM Spectrum includes radio, microwave, infrared, visible, ultraviolet, x-rays, gamma rays; light particles at different wavelengths

Flare

Coronal Mass Ejection (CME)

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

Break of a prominence

Big area of Sun

Difference Between a CME & Solar Flare

Comparison video of a Solar Flare (small, localized region) and a CME (big region of the Sun)

http://cse.ssl.berkeley.edu/coronalweather/CMEsFlares/

Coronal Mass Ejection – Problems for Earth and Earthlings(http://hesperia.gsfc.nasa.gov/sftheory/spaceweather.htm)

• Communications – Radio, TV, Cell phones, Over-the-Horizon radar, jamming of air-control radio frequencies (long distances)

• Navigation Systems – LORAN, GPS – degrades orbit• Satellites – Heat atmosphere and expand it, changing satellite orbit Electronics fried by energetic particles• Radiation Hazards to Humans – astronauts going to Moon or Mars,

airplane crews and passengers (small)• Electric Power grids – ex 1989 in Canada

• Global Climate affected by solar cycle maximum & minimum– Link between solar minimum and “the little ice age” 1500 to 1850

• Biology – ex homing pigeons, dolphins, whales (use Earth’s magnetic field to guide them)

Star PowerOr How I Learned to Love

Fusion

• Gravity pulls in

• Energy from fusion pushes out

Balance -Hydrostatic Equilibrium

• Mash light elements together • Form heavier elements + release energy EX: 4H 1He + 2e+ + 2e + energy more mass less mass E = mc2

Sun is giving off mass and losing gravity. Fusion will make the Sun larger over a long time period.

Fusion

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

• Continuous flow of particles from Sun

- Protons, electrons, ions

http://learn.arc.nasa.gov/planets/0/

Solar windEarth’s

magnetic field

Solar windEarth’s

magnetic field

Charged particles spiral toward poles

Solar windEarth’s

magnetic field

Charged particles spiral toward poles

Charges interact with

Earth’s atmosphere

Solar wind

Charged particles spiral toward poles

Energy released

Charges interact with

Earth’s atmosphere

Earth’s magnetic

field

MMS Spacecraft• Launched March 12, 2015• http://mms.gsfc.nasa.gov/• Earth’s magnetosphere as a

laboratory to study the microphysics of magnetic reconnection

http://mms.gsfc.nasa.gov/

CRT and Magnet

https://www.youtube.com/watch?v=YbzBTdU7iRU

APOD - Edmonton

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 Station

https://www.youtube.com/watch?v=FG0fTKAqZ5g

Aurora on Other Planets

http://antwrp.gsfc.nasa.gov/apod/ap011114.htmlshort motion clip

Space Weather Prediction Center http://www.swpc.noaa.gov/SWN/index.html

http://www.swpc.noaa.gov/ovation/

Aurora review

http://climate.gi.alaska.edu/Curtis/pom.jpgVideo

• http://apod.nasa.gov/apod/ap101124.html• Or http://vimeo.com/16917950 • End

Safe Gazing at the Sun

• Observation March 31 or April 2• Date depends on weather

• Handout or get information from class website• Lab Students need to follow the lab prep work on lab

page of website• Lecture for the day and lab for the week• ~8:30am to 3:30pm reserve 30 minutes for lecture or 1

hour for lab