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Milky Way Galaxy
Derived name from Goddess' breast milk. "milky streak from breast milk squirting across the sky.
Shape- Swirling (spiral) pinwheel/wagonwheel
Size- 100,000 light years across..18,000 light years thick (pancake)
Position of the sun- 2/3 of the way out from the center. (Orions arm)
duration of spin- rotation:250 million years from the sun to go around, or 1 galatic year.
The study of galaxies. Glob ---->primortial atom.
primortial atom exploded and scattered particles all over the universe. Made mini-universes called galaxies which came together in little neighborhoods.
our little neighborhood. Local group 30 galaxies in our neighborhood: Milky way, large machalini cloud, messwar catalog=M infront (M31-closest spiral to milky way)
Dominated by 2 spirals (milky way & m31) andromeda= 2 1/2 billion light years away.
Between milky way & andromeda galaxies theres an empty void--absolutely nothing anywhere (stars, rocks, etc)
Milky way and andromeda.
Nucleus with arms swirling around the outside. (Swirling wagonwheels)
egg shaped. billions of stars real close together
Clouds of stars. Not in any particular shape.
(ex) Large & small magellini clouds.
Can be seen in the southern hemipshere (peru, venezuela)----the whole galaxies
Evolution of Galaxies
Change with time.
Irregular are the young galaxies
Spiral are the middle/youth galaxies (sometimes sm nucleus w many arms, sometimes big nucleus with one arm)
Elliptical are the old galaxies
- 2 theories:
- ~pressure builds & builds -->irregular galaxies again
- ~gigantic black holes- pulls stars in-->worm hole-->new universe.
National General catalog
Stellar evolution- (Beginning)
Nebula- large swirling cloud of gas and dust
Bright Nebula- stars are close enough to light it up (lagoon nebula, veil nebula, north american nebula)
Dark Nebula- block out light from stars (ex=horse head)
orion & great nebula can only be seen with the naked eye
BIRTH: PROTOSTAR: newly born star. When nuclear reaction begins and the cloud begins to shine under its own pressure.
Stellar evolution: youth/middle age:
The star that burns its fuel (hydrogen gas). "most stars are in this stage"
90% of a stars life, 9/10 of stars are in this age
Big cloud-->big stars in vice versa
***Rigel, Regulus, Achernor, Vega, Sirius, Sun, Acturus***
Stellar evolution: Old age
seen in two ways.
1. red giant- betelgeuse. swells into a gigantic ghost because pressure in doesnt equal gravity in. Runs out of gas
2. Pulsating star- (called a cepheld variable) star gets bright and dim because of the pressure changing. Visible change every 3 days- delta cepheus.
Death of a star: 3 ways
1. Big- black hole. star collapses/imploded star (gravity collapses)
2. Medium-super nova. star that blows up. (super nova 1054- showed up in taurus) crab nebula
3. Small- Black dwarf- small stars that die (fades away) and turns into a planet. burnout (Earth)
---our sun= 3rd generation star--3 times life. 864,000 miles across. Black hole=4 miles across.
(H-R) Hertzsprung Russel Diagram- graphical stellar evolution
mass luminosity relation: small stars are the faint stars, big stars are the bright stars.
Luminosity- Real brightness or absolute magnitude
B- (blue white)- 20,000
A- (white) 10,000
90% of stars are in a diagonal line.
Nebular Condensation Theory
Most scientifically accepted theory. (not theological). Large swirling cloud of gas & dust. Condensing cloud got smaller to make the sun 4 1/2 billion years ago.
When the cloud reaches 10 million degrees nuclear reactions occur.
Einsteins equivalence postulate: E=mc^2
Proton-Proton (thermonuclear) fusion: 36 steps
Two hydrogen nuclei fuse together & make byproduct and Energy. (fuel--H + H= helium & energy--byproduct)
Hydrogen burns to make nuclear energy and only when very, very hot.
The moment the sun ignited for the first time, a burst of energy sent out in all directions & pushed out of the solar system (small stuff)
"bubble that surrounds the solar system (just ours). Kuipper belt, Heliopause, etc is the boundry of the oort cloud (suns gravity)
Thermostatic (hydrostatic equilibrium)
**JUST EQUILIBRIUM ON TEST**
The sun isnt expanding or collapsing (equilibrium)
Heat--wants to blow it up
Gravity--wants it to collapse
*Pressure of the sun out= equals the pressure of the gravity in*
Characteristics of the sun: Real diameter, angular diameter, apparent magnitude, absolute magnitude, distance from earth
Our sun is a dwarf compared to others.
Real diameter- 864,000 miles (110 earths on a necklace)
Angular diameter- big object when looking from Earths sky. 1/2 degrees (dime at arms length)
apparent (bright)~ -27
--distance from earth 1 AU (93 million miles)
Characteristics of the sun: surface temp, chemical composition, density, volume, mass
Surface tempature- color yellow- roughly 5000 degrees
Chem- 74% hydrogen, 24% helium---98% H & He (fuel & byproduct)---- 92 naturally occuring elements found on the sun. #92 uranium. 1% O, .4% C, .16% Fe, .1% silicon
density- 1.4 little more than water
volume- 1.3 million earths
mass-(weight) 330,000 Earths
Layers of the sun (matching)
Core---radiative zone----convective zone
Sun is 16 million degrees--10 million=nuclear reaction. Takes 50 million years from core to sun (energy)
Core-center of the sun (highest temp & pressures) only place nuclear reactions are occuring. (nuclear furnace)
Radiative zone- thickest layer- layer of transfer from core out. Energy is transferring out.
Convective zone- radiative zone reaches surface (which is cooler). Cooling down the gases makes the gas heavier and sink. billions of gas bubbles rising and falling because of the temp difference. Gas gets heavier and sinks right under surface.
Photosphere, granulation, sunspot
Photosphere: The visible surface of the sun---yellow
Granulation: bright- gas bubble reaching top, dark spots sinking gas (salt & pepper)
Sunspot- out of control dark granule (huge dark spot). cooler region of the sun. umbra-darker, preumbra-lighter.
Sun flare, prominence
flare- out of control bright flare/spot/granule
prominence-explosive flame shoots out through a flare at the surface of the sun. loop prominence--loops back
chromosphere- redish, orange, pink (inner atmosphere) 4000-3000 degrees. reversing layer top goes up temp.- usually invisible except during an eclipse
corona- outer atmosphere temp 500,000 degrees. not much heat bc its spread out. size changes w activity. max=big min=small
solar wind- coronal mass ejection. coronal holes let little energy fly out in all directions.
aurora borealis- natural light display in the sky (antartica, etc) high latitude regions. Collision of energetic charged particles w/ atoms high in the high altitude atmosphere.
Rotation: spin. track sunspots b/c they last 60 days--approximately 30 days to go all the way around (period of rotation).
- sun spots are in pairs (one positive and one negative because theyre magnetic.
- 25 days to spin at the equator. 35 days at its poles.
orbit--at center of nucleus (black hole?) sun isnt at the nucleus, its out from the arms. 250 million years period of revolution (galactic year)
sun is 18 galactic years (traveled around the milky way)
suns maximums & minimums
maximums- every 11 years (1981, 1992, 2003 etc). Drought, why we dont have winters (this year) & spring is early because of approaching maximum. war falls on every maximum
minimum- lot of rain/snow, depression, recession. every 5 years theres a minimum.
first person to find sun spots & that it spins.
father angelo secci
chief astronomer, observations in rome, spectroscopy & discovered something at the center of the sun (the body of the sun). Chemicals-H, Ca, Fe, He. The sun is a star
made first solar observatory & sun spots are magnetic. Analyzed surface of the sun. Magnetic fields because of line in sun spots.
made an artificial aurora nothern lights
solar carpuscular radiation- effects comet tails, cant penetrate coronas.
Suns gravity too big to allow SCR
solar wind- both right- calculated suns corona. (equator-constant stream goes into space from sun). Thermal energy enough to push away from gravity 300-800 km/sec. wind always there & never quit
How far does the sun go? Kuipper belt, oort cloud, heliopause (all the same thing)
BP- people are curious abt the life of stars
LB-searches for protostars
HB-explained the fusion process
MD-observed super nova 1987-A.
Origin: dark clouds like rosette nebula (bright)
Birth: protostar when e=mc^2
youth/middle age-burns steadily
Old age- runs out of hydrogen fuel & becomes unstable
Death- small die quietly by fading away; medium explode like super nova, and large collapse like a black hole.
apparent change in astronomical position- the apparent change in position of an object when viewed from the earth and the sun.
displacement/difference in apparent position of object viewed from two lines of sight.
d=1/p find distance in parsecs
parsec- unit of length- approx 3.26 light years=just over 19 trillion miles (distance object seems to move just one arcsec of parallax
LY- the distance light travels in a vaccum in one julian year (3.26 LY=1parsec)
Apparent-brightness of a star (object) seen from earth. Hipparchus made a scale of brightness 1(B)---6(F).
Absolute- real brightness (luminosity) Have to be side by side to see which is brighter. closer objects are brighter.
Sun is brightest in earths sky (5000 total w naked eye)
orion the hunter
brightest star in the earths sky
the most luminous star
physical characteristics test:
temp, radial velocity, proper motion, star heat, gas
temp- black body exp (obj doesnt give off own light & weins law---colors and degrees
radial velocity-comes towards/away from you--dopplar effect. brighter/louder
proper motion- when a star moves across the line of sight with cameras
why stars hot? nuclear processes, fision & fusion...mostly fusion
main gas- Hydrogen