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Astro Quiz 3
Light!, tels, atm, spectroscopy, E, mag fields, solar system
73
Astronomy
Undergraduate 1
10/17/2009

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Term
(4)magnifying pwr
Definition
ability of tel to make imgs look bigger. M=Fo/Fe. Fo=focal length of primary mirror. Fe= focal length of eyepiece
Term
(2)lger lens D =>
Definition
better lt-gathering pwr and res
Term
(1)longer tel =>
Definition
better magn
Term
professional tel is...
Definition
1-11 m in D
Term
(3)trad tel has...
Definition
1. main, primary mirror (big, sturdy)

2. secondary mirror (smaller)

curved mirrors used to focus lt
Term
(3)modern tels have
Definition
1. lter mirrors, so tel can be lger

2. dynamic control by comp

3. simpler, stronger structure so mirror wont distort
Term
(2)seeing=
Definition
refraction of lt f Es atm t limits res. weather conds and turbulence t limit qual of astroic imgs
Term
human eye has res
Definition
13" (arcsec)
Term
res form
Definition
alpha is proportional to w/D. res in arcsec
Term
Es res limit
Definition
.3-.4" is best res you can get due to Es atm
Term
(2)good conds for tels:
Definition
far away f civn, high up
Term
lg amt of em radn is
Definition
absorbed by Es atm
Term
twinkling stars due to...
Definition
motion of gas in atm
Term
astroers can take info f
Definition
full spectrum of sources, g-rays to radio waves
Term
(4)tels are used
Definition
to gather more lt f astroic objs. makes them look nearer, bigger, brighter
Term
(3)refraction
Definition
lt bending as it enters a medium. i= angle of incidence, r= angle of refraction
Term
refracting tel
Definition
curved lens focuses lt into focal pt, on focal plane behind tel
Term
(2)atm is opaque
Definition
at very short and very long w's
Term
bc of refrn, we can...
Definition
see sun after it has set
Term
(4)greenhouse effect=
Definition
Es surface hted by suns radn. Re-radiates ht e as IR radn, wh is absorbed by co2 and other atmic gases. This traps ht in Es atm
Term
(3)ge is...
Definition
nat and necessary to keep E at comf temp. wo it, E would be -20C
Term
Es atmic co2 content has
Definition
increased exponentially for last 300 yrs
Term
(3)plt's climate deps on
Definition
mass, d f sun, atmic comp
Term
(3)Es atm consists of:
Definition
n2 (75%), o2 (23%), others. co2 (.05%). also He, Ar, h2o, Ne
Term
(2 huge)o2 comes f...
Definition
photosynthesis. converts sunlt and co2 into chem e, producing o2 as biproduct. o2 has been increasing as fraction of Es atm since phtsths rose 3bil yrs ago
Term
(3)space tels are good bc
Definition
above atm, can see at all w's, stars dont twinkle (gases)
Term
(2)IR astro
Definition
can only be obsed f hi mt tops or airplanes, bc most IR radn is absorbed in lower atm
Term
(2)UV astro
Definition
must be done f sats bc UV radn is completely absorbed in ozone layer
Term
X-ray astro
Definition
must be done f sats
Term
(2)gamma-ray astro
Definition
traces most vio process in U, g-rays have most em radn
Term
radio waves
Definition
can be obsed f ground bc they penetrate Es atm
Term
lgest radio tel
Definition
300m in Arecibo, Puerto Rico
Term
spectral lines
Definition
tell us ab chem comp and other props of obsed obj
Term
spectrograph
Definition
is used to obtain spectrum of obj
Term
(4)res at radio w's
Definition
is bad bc theyre at the lower end of em spectrum. need lg lens to get resolving pwr. hay radio wave pollution f cell phones, sats. some ppl want to build radio tels on far sd of moon
Term
radio interferometry
Definition
combining signals f several smaller tesl to sim one big mirror. Ex: Very Lg Array (VLA) 27 dishes arranged to sim 36-km dish
Term
(4)radio astro
Definition
reveals several features not vis on other w's, bc they penetrate gas and dust clouds. can obs radio waves where vis lt is conpletely absorbed (ex: neutral H clouds, wh contain 90% all mols in U)
Term
CCD=
Definition
change-coupled device
Term
(6)CCDs are better th photos bc
Definition
they are quantitiative, more sensitive, can be easily maniped on comps and read into comp mems, never fade, show contrast/brightness
Term
diffraction grating
Definition
plate full of very narrow slits t causes waves to interfere, splitting up into colors
Term
we study spectrum of star to
Definition
see the gases present and learn ab its chem comp
Term
(2)res=
Definition
the lvl of detail a tel is capable of revealing. is fundly ltd by wave nature of lt
Term
(4)scattering
Definition
random redirn of lt wave or photon as it interacts w atoms or dust particles in its path. deps on w and sx of scattered partle L
Term
extinction
Definition
dimming of starlt due to absorption and scattering by interstellar dust parts
Term
focal length
Definition
d bw lens and focal plane
Term
(2)lt-gathering pwr form
Definition
A=(pi)(D/2)^2. Lt-gathering pwr is proportional to D^2
Term
(2)resolving pwr
Definition
smallest angular d bw 2 objs t can be sep.ed by a tel of diameter D. a(min)=1.22(w/D)
Term
resolving pwr for optical w's=
Definition
a(min)=11.6arcsec/D[cm]
Term
better magnifying pwr
Definition
does NOT mean better resolving pwr
Term
(10)formation of E
Definition
4.6bil byrs ago. Gases and dusts coalesced ihop, shockwave shot thru, huge spheroid formed. Diff.n produced dense core, thick mantle, low-density crust. Heavily bombarded in debris-filled early solar sys. Flooded by molten rock and later water-filled lowlands.
Term
Es mean surface temp
Definition
8-11deg C ? (288-293K)
Term
2 sources of ht in Es interior
Definition
potential e of infalling material, decay of radioactive material
Term
Es orig atm consisted mostly of
Definition
H and He
Term
Es secondary atm
Definition
outgassing thru volcanism (eruption) created heavy elements like co2 in atm
Term
(4)atm loss
Definition
mols can esc atm if they achieve esc v. deps on mass, atmic comp (mol masses), temp, type of rot pd
Term
(2)mols' spd deps on
Definition
temp of gas and mass of indiv mols
Term
(3)esc v deps on
Definition
plt's G (therefore its r and mass)
Term
(2)=librium
Definition
forced bal. upwards pressure = dnwards G.al force
Term
(3)comp of Es atm infled by
Definition
chem reactions, energetic radn f spc (UV in particular)
Term
blue lt
Definition
scattered out of sunlt more th red lt. (ex: blue sky, red sunset)
Term
(2)albedo=
Definition
reflectivity= ability of surface to reflect lt
Term
(3)albedo infled by
Definition
more ice= more reflective E. so2 emissions t produce sulfate parts in Es atm (reflect some lt back into spc, wh lds to cooling)
Term
cooling factor:
Definition
volcanic eruptions
Term
(3)human effect on atm
Definition
damage of ozone layer due to increase of CFCs. UV radn has damaging effects on human and animal tissue
Term
(5)Es mag field
Definition
carries mag forces. causes compass needle to pt towards it. dipole. inclined at 12deg to rot axis. many astroic objs have mag fields.
Term
(5)causes of Es mag field
Definition
mag dynamo (electric currents flowing thru Es molten iron core). metallic lqd is hted internally->convection, metallic->conduction, Es rotn->lqd rotn, dynamo)
Term
(2)cause of magnetosphere
Definition
mag field strength decreases 1/r^3 (exponentially). mag fields infl extends into spc beyond atm. hence, magnetosphere
Term
(4)solar mag field
Definition
dipole. is carried away f sun by solar winds. mag field lines are roughly parallel. interacts w Es mag field
Term
aurora borealis
Definition
Nern lts
Term
aurora australis
Definition
Sern lts
Term
(7)cause of aurorae
Definition
high-e partles f sun enter Es atm thru polar cusps or esc f Van Allen belts and gap. they collisionally excite atoms and mols, wh emit vis lt to get back to ground state. Charged partles f sun move thru Es mag field and strike upper atm
Term
(4)Es atm layers
Definition
troposphere (dense lower layer), stratosphere (more stable), ionosphere (most mols and atoms have broken apart), exosphere
Term
V(sphere)=
Definition
4(pi)R^3/3
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