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Astronomy Test 2

Terms in this set (116)

Red shift
(astronomy) a shift in the spectra of distant galaxies toward longer wavelengths
hot dense objects
...
Wavelength
the distance between wave crests
frequency
measures how frequently the wave passes
wavelength and frequency are
inversely related
electromagnetic waves
light propagates through space via alternating electric and magnetic fields
propagation of light
as light radiates away, its energy spreads out over a greater area causing the photons to appear fainter
dispersion
the spreading of a beam of light into its different light waves according to its wavelength
electromagnetic spectrum
the range of wavelengths or frequencies over which electromagnetic radiation extends (radio, microwave. infrared, visible, ultraviolet, x ray, gamma ray)
blue shift
A decrease in the wavelength of radiation emitted by an approaching celestial body.
Energy of a photon is
proportional to its frequency
inversely proportional to its wavelength
Kelvin scale
scale with lowest theoretical temperature (absolute zero)
doesn't account for thermal motion
blackbody
A hypothetical object that is a perfect absorber and emitter of radiation at all wavelengths
planck curve
(blackbody curve) Shows relationship between the blackbodies intensity at every wavelength when heated to a given temperature
Wien's Law
blackbodies peak wavelength is inversely proportional to its temperature
(the hotter an object is, the bluer it will appear)
Steffan-Boltzmann Law
even a slight increase in temperature leads to a huge increase in flux
hot objects radiate more at all wavelengths
Luminosity
The amount of light leaving a star per second (measured in watts)
The hotter or larger the star...
the more luminous
temperature and luminosity
luminosity is proportional to its temperature to the 4th power
Radius-luminosity
luminosity is proportional to radius squared
Brightness of a star
proportional to luminosity
inversely proportional to distance squared
electrons
occupy all the space around the nucleus in a "cloud"
Bohr Model of Hydrogen
-model based on the electron in a hydrogen atom traveling around the nucleus in one of an array of concentric orbit. movement from a higher n level to a lower n level releases light.
Absorption
the process in which a electron absorbs the photon and moves up an energy level (ex: N=2 to N=3)
The array of colors will be shown but it will be missing the absorbed photon's color- absorption lines
Emission
when an electron releases a photon/ or energy and moves back down an energy level (ex: N=4 to N=2)
Only the emitted photon's color will be shown through a prism- emission lines
Hydrogen atom quantized energy state
n2 =656nm
n3 =486nm
n4 =434nm
n5 =410nm
Each element has its own unique set of
energy levels
Ionization
electron absorbs enough energy to leave the atom
Emission lines from ionization
When an ionized electron finds another atom missing an electron, the electron then emits the original photon
when a hot, dense object's light passes through a prism it creates a
continuous spectrum
When a hot, dense object's light passes through a cloud of cool gas it creates a
absorption spectrum
When a gas is heated and then passed through a prism it creates a
emission spectrum
Doppler Shift
waves compress to shorter wavelengths when in direction of motion, and stretch to longer wavelengths behind
Blue shift
Shorter wavelengths that are given as an object in space move toward an observer.
red shift
longer wavelengths that are given as an object in space moves away from an observer
How to tell if a star is coming toward or going away
find the change in wavelength (observed wavelength - rest wavelength)
If the value is negative (less than 0) it is blue shifted
If the value is positive it is red shifted
radial velocity
proportion to doppler shift (ex: if coming toward us at twice the speed, it will be blue shifted by twice its amount)
what makes up the sun
Hydrogen= 92%
Helium= 7.8%
"metals"= .1%
The Core
the center of the sun(unbelievably high pressure and where electromagnetic radiation is created)
Radiative zone
carries energy via radiative diffusuion (Photons of light radiate from here and go on the "random walk" in this zone for a long time)
Convective zone
carries energy via convection (like boiling water)
Photosphere
"'surface" where the light escapes
granules
"tiny" (the size of texas) convection cells in the photosphere and bring energy out
Sun spots
cooler and darker regions on photoshpere of Sun
(still very bright)
Chromosphere
lower atmosphere of the sun
has a higher temperature than the photosphere
Corona
outer atmosphere of the sun
(seen through solar eclipse)temperatures are even hotter than chromosphere
transition region
the region in the Sun's atmosphere where the temperature rises very rapidly from the temperatures that characterize the chromosphere to the high temperatures of the corona
Coronal holes
open magnetic field lines stretching out into space
- gasses then escape and form solar wind
Solar wind
caused by coronal holes and is 1 million mph
In order for an electron in a hydrogen atom to increase its energy level from n=2 to n=3 it must
absorb a photon with a wavelength of 656 nm
when light from a hot dense object passes through a prism a ________ spectrum is produced
continuous
When light from a hot dense object passes through a cloud of cool gas before it is passes through a prism, a ____________ spectrum is produced.
absorption
An atom is ionized when it _________ a photon of very __________ wavelength, causing the electron to leave the atom entirely.
absorbs; short
If an electromagnetic wave's frequency is increased, then
its energy increases, the wavelength decreases, and its color gets bluer
The energy required to transition a photon from n=3 to n=5 in a hydrogen atom is ___________ the energy required to transition from n=5 to n=2
less than
True or False: the Angstrom, nanometer, and meter are all used to measure wavelengths
true
As a blackbody become hotter, it also becomes _______ and ___________
more luminous and bluer
Star A and star B appear equally bright in the sky. Star A is twice as far away from Earth as star B. How do the luminosities of stars A and B compare?
Star A is 4 times as luminous as Star B (distance squared)
The temperature of an object has a very specific meaning as it relates to the object's atoms. A high temperature means that the atoms
are moving very fast
Twos stars are of equal luminosity. Star A is 3 times as far as star B. Star A appears ________ Star B
1/9 as bright as star B
When an electron moves from a higher energy level to a lower energy level
a photon is emitted
The transition region is only 50km thick, yet temperatures can suddenly jump from about 10,000 K in the _______________ to 1,000,000 K at the ____________
chromosphere; corona
The Sun's photosphere is segmented into small (1000km) convective cells called
granules
The sun's atmosphere is divided into:
the core, the radiative zone, the convective zone
The sun is mostly made up of
hydrogen
Charged particles escape from the sun via ________, forming the ____________.
coronal holes; solar wind
sunspots
cooler regions of the photosphere (darker relative to the rest of the sun)
sunspots are
regions of magnetic activity
sunspots typically form in
pairs
Sunspots ___________ their latitude throughout their life cycle
change
Sunspots taper off near the
equator
Sun is a solid body
false
The sun has multiple rotational periods:
it rotates _______ at the equator and _______ at the poles
faster;slower
Differential rotation of the sun
the equatorial regions of the sun rotating more rapidly than the polar regions.
What is a major reason why there is a continuous cycle of sunspots
differential rotation
When magnetic field lines twist and tangle up they occasionally will snap/pop forming
sunspots
sunspots occur in a cycle of around _____ years
7 years
prominences
Huge loops of gas (can be very large)
Flares
violent, rapid erruptioms (magnetic field lines that reconnect and "short out")
solar min: 1 per week
solar max: 1 per day
CME (coronal mass ejection)
Large-scale solar event involving an ejection of hot plasma that may accelerate charged particles and travel as far as the Earth's orbit, preceded by a shock front that may create a magnetic storm on Earth - can be seen as an aurora (Northern Lights)
Coronal loops
magnetic field lines that trap charged particles
Filaments
prominences seen in silhouette (cooler and darker)
Nuclear Fusion
occurs in the core of the sun
protons normally repel each other but the pressure and temp in the core are so high that they fuse together instead
The ____________ is responsible for about 85% of Sun's energy
proton-proton chain
hydrostatic equilibrium
The balance between the gravity (pulling inward) and the pressure (pushing outward) of the sun
Radiative Diffusion
gamma rays radiated from the core go on a "random walk" in the radiative zone. It dilutes the radiation and makes the photons lose energy.
Neutrinos
emerge from the sun right away (ninja particles)
Helioseismology
Analyzes the sun's vibrations to determine its internal structure
Protostar
the earliest stage of a star's life
- forming at center of collapsing molecular clous
- temp/pressure not high enough for fussion
Circumstellar disk
a broad ring of material orbiting a protostar
protoplanetary disk
flattened outer part of the disk that did not become part of the star
accretion disk
inner disk that feeds the protostar
angular momentum
mass:
rotational velocity:
distance of mass from axis:
T Tauri Stars
"late term' protostars
- aren't yet fusing H but will soon
- strong stellar winds
jets
outflow (disk material) being channeled through the poles
Herbig-Haro objects
high velocity jets that slam into and ionize interllar gas
Transit method
way to detect exoplanets by measuring the lowered brightnessed due to the planet crossing the star
How to find orbital period using transit method
repeating drop offs in light signal a exoplanet. The time between drop offs is the orbital period
limiting factor of transit method:
requires a edge on view
direct imaging
artificially block out the sun's light to locate exoplanets
limiting factor of direct imaging:
only massive planets that are far away can be detective because those two small/close will be blocked out with the sun
eyeball world
planets that are tidally locked to their star and are slowly vaporizing
only a planet's ________ mass can be known if its _________ is unknown.
minimum;eccentricity
a _______ forms at the center of a circumstellar disk
protostar
What kinds of planets does the transit method detect most often
planets that are viewed from edge on to our line of sight
When does a protostar become a star?
when the temperature and pressure are high enough to ignite HYDROGEN FUSION in its core
What method of detecting exoplanets involves blocking the star's light?
direct imaging
what method of detecting exoplanets involves detecting periodic changes in a star's apparent brightness?
transit method
what method of detecting exoplanets involves detecting periodic changes in a star's doppler shift?
radial velocity
what method of detecting exoplanets is capable of detecting multiple planets in a system
all three (transit, direct, radial velocity)
Which two forces establish hydrostatic equilibrium in an evolving protostar?
pressure and gravity
Why do protostars blow their stellar winds in bipolar outflows?
The circumstellar disk confines the protostar's wind outflow to the poles
What do we need to know about a planet to determine if it is capable of supporting life?
distance from sun, atmospheric composition via spectroscopy
What kind of planets does the direct imaging method detect most often?
massive planets that orbit far from their host star
What kind of planets does the radial velocity method detect most often?
massive planets that orbit close to their host star
Why does a collapsing cloud flatten as it rotates?
the cloud rotates fastest at its equator, which pushes infalling material away
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