Astronomy Rough Notes – Sun, Fusion, Aurora
DISCLAIMER: These notes do NOT cover everything you need to know. You may need to look up some
item or concept online or in a text. Test questions are not exact copies of the OBJECTIVES but if you
know the OBJECTIVES thoroughly, you should do well on the exams.
HANDOUTS:
None
GOOD REFERENCE:
http://solarscience.msfc.nasa.gov/
OBJECTIVES:
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 Sun’s “surface” and the Earth’s surface 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, GENERAL: (Don’t memorize numbers except as noted)
Size:
109 Earth’s can fit across the diameter of the Sun (learn about 100 Earths across Sun)
Recall scaling:
Your photo of Sun and Earth
~If Sun is a beach ball, then Earth is a BB about half a football field away (you
know this already).
Composition:
By counting atoms ~90% H, ~10% He, a few other elements like C, Si, Fe (learn these numbers)
By mass: ~75% H, ~25% He, (learn these numbers)
Temperature:
Surface: ~5800 K (~10 000 degrees F)
Core:
~15 000 000 K (~27 000 000 degrees F)
Mass:
~1030 kg
Top 10% of mass compared to other stars
Most of mass of solar system (99.8%)
Rotation:
Equator ~25 days, latitudes slower (as much as 10 days)
View of latest rotation at http://soho.nascom.nasa.gov/data/LATEST/current_mdi_igr.mpg
Another image at http://www.physics.hku.hk/~nature/CD/regular_e/lectures/chap11.html
References:
http://sohowww.nascom.nasa.gov/
http://www.nineplanets.org/sol.html and many others
http://www.sec.noaa.gov/primer/primer.html
http://solarscience.msfc.nasa.gov
SUN, EXTERNAL VIEW:
(DO NOT LOOK AT THE SUN UNLESS UNDER EXPERT GUIDANCE)
General references:
http://sohowww.nascom.nasa.gov/
http://observe.arc.nasa.gov/nasa/exhibits/sun/sun_1.html
Corona
Gas around the Sun – visible during an eclipse
See http://antwrp.gsfc.nasa.gov/apod/ap031122.html
Photosphere
The surface you “see”
Sunspot
Magnetic storm on the photosphere
Much cooler than surrounding area (~3800 K) - still hot but looks dark
Energy prevented from flowing upward
Sunspot cycle
Average 11 year cycle from solar max through solar min back to solar max
Flare
Prominence (video clip: ProminenceChange.mov)
Very detailed picture http://www.lmsal.com/Press/spicules2004/
Coronal mass ejection (CME)
Really massive ejection of solar material
See “Hot Shots” in http://sohowww.nascom.nasa.gov/
Also go to http://sohowww.nascom.nasa.gov/hotshots/2000_02_26/c3sm.mpg
Problems for Earth and Earthlings (See http://www.sec.noaa.gov/primer/primer.html )
Communications – Radio, TV, Over-the-Horizon radar, jamming of air-control radio frequencies
Navigation Systems – LORAN, GPS
Satellites –
Heat atmosphere and expand it, changing satellite orbit
Electronics fried by energetic particles
Electrical discharge across components (differential charging)
Radiation Hazards to Humans – astronauts, airplane crews and passengers (small)
Geologic Exploration
Electric Power grids – ex 1989
Pipelines - flow meter readings and corrosion
Climate
Biology – ex physically stressed humans, homing pigeons, whales
Video clip (eit-195-200401.mov)
NASA – STEREO A of CME
http://science.nasa.gov/science-news/science-at-nasa/2011/18aug_cmemovie/
NASA – Science News – Good article on CMEs and a near miss
http://science.nasa.gov/science-news/science-at-nasa/2014/23jul_superstorm/
SUN, POWER SOURCE:
See http://observe.arc.nasa.gov/nasa/exhibits/sun/sun_5.html and others
Fusion in the core
Light elements like H fuse to form heavier elements like He
Release energy in process
4 H mashed together form 1 He BUT
4 H have more mass than 1 He
That missing mass was converted to energy
E = mc2
Every second, our Sun converts 600 million tons of H into 596 million tons of He + ENERGY
Gravity does the mashing
Sun like stars produce He…C
AURORA:
Aurora pictures at:
http://science.nasa.gov/headlines/y2003/24mar_noseprints.htm?list687798
http://www.colintyler.com
Beautiful video here: http://apod.nasa.gov/apod/ap101124.html or http://vimeo.com/16917950
Good explanation/video at [email protected]
Explanation
http://learn.arc.nasa.gov/planets/0
Particles from Sun interact with Earth’s magnetic fie
Demo: CRT
Particles collide with Earth’s atmosphere releasing e
We see as aurora (northern and southern lights).
See www.spaceweather.com for aurora alerts
For a map of the auroral arc, see http://www.swpc.noaa.gov/SWN/index.html
HOMEWORK:
Read about the Sun
Make flash cards for the objectives above.
Review previous flash cards.
Revised 6 January 2016