Galaxy and Universe Final exam Flashcards
What is the surface temperature of the sun
5800K
in the core of the sun where nuclear fusion takes place. which method is responsible for the transport of energy
Radiation
starting from the center of the sun moving outward, order the layers of the sun
radiative zone, convection zone, photosphere, chromosphere and corona
the temperature of the sun is approximately what temperature
15 x million kelvin
the majority of the suns energy come from what
hydrogen fusion
the energy that fuels the sun is generated from where
the core
what makes up 29% of the suns radius
the convective zone
plages that are around sun spots appear brighter because of what
higher temperature
what is associated with the solar magnetic field
sunspots, prominence, coronal mass ejections, solar flares
when will the sun likely stop being a main sequence star
around 5 billion year
what is the temperature of the corona
1,000,000 K
where does most of the light from the sun originate from
photosphere
what is the most important characteristic of a star
its mass
what is hotter a red star or a blue star
blue star
spectral class q
OBAFGKM
what spectral class is the sun
G2
After hydrogen what is the second highest element in a star
helium
what is the mass range for main sequence stars
0.08 to 100 M
stars located on the main sequence are called what
dwarf stars
on a typical H-R diagram where are the stars with the smallest radii located
lower left corner
the one property of a main-sequence star that determines all its other properties
its mass
In an H-R diagram stars with the coolest surface temperature and highest luminosity are found where in the diagram
upper right corner
stars that have the smallest radii are classified as what
white dwarfs
binary stars are the most important for the determination of stellar what
mass
a main-sequence star is unique because
nuclear fusion of hydrogen occurs in its core
at the end of the proton-proton chain of nuclear fusion in the sun, hydrogen nuclei have been converted into what?
helium nuclei
Radiative transfer
emission and absorption of gamma-ray photons repeatedly, slowly degrading to lower energy photons which work their way to the surface
convective transport
hot cells become buoyant and rise, cells cool and fall
Helioseismology
sun vibrates or rings in very complicated patterns
photosphere
origin of all the visible radiation, about 400Km in depth and with an average temperature of 5800K
Solar spectrum
photosphere is complicated with 100,000’s of absorption lines of more than 70 elements
chromosphere
average temperature of 10,000K
corona
outermost layer reaching temperature of 1 to 2 million K visible during solar eclipse or coronagraph
solar activity
effects of magnetic fields on charged particles which must move along lines of magnetic field
coronal mass ejections (CME’s)
occur in coronal holes mass loss gives rise to the solar wind
sunspots
rotate with periods of suns rotation faster at the equator and slower at higher latitudes. average of about 28 days
umbra
darker spot of sunspot about 2000K cooler than sun’s surface
sunspot cycle of solar activity
takes an average of 11 years
prominences
ejections of mass along magnetic lines
flares
violent eruptions with temperatures up to 20 million K source of intense Gamma and x-rays
measuring the color of stars gives us what
surface temperature
color indezx
B-V blue stars about -0.4 and cool red stars about +2.0
radial velocity
present only if star is moving towards or away from the observer
Tangential velocity or proper motion
only perpendicular to the line of sight
Radial velocity and Tangential velocity
add together to form space velocity
composition of the sun
74.5% H, 23.7% He, 1.8% metals
stellar masses
most important property of stars
binary stars
the means for finding masses. the more massive a star has a smaller more elliptical orbit and less massive star has a larger orbit
visual binary
two stars seen slowly orbiting around their center of mass. can get the masses of both stars from this
spectroscopic binary
seen as only a single point of light but on spectrum see two sets of absorption lines, cannot get masses directly
Masses of stars on main sequence
vary from 0.07 to 100M
Horizontal Axis of H-R diagram
represents temperature
stars in upper right corner of H-R diagram
cool but very luminous supergiants
stars in lower left corner of H-R diagram
very hot and very faint small white dwarfs
stars in upper left corner of H-R diagram
very hot and luminous massive o stars
stars in lower right corner of H-R diagram
cool and small. Red dwarfs
what classifies stars to be on the main sequence of H-R diagram
hydrogen being fused into helium in their core
class Ia and Ib stars
supergiants
class II stars
bright giants
Class III stars
giants
class IV stars
sub giants
Cepheid and RR lyrae stars
pulsating variable stars
cepheids
light curve gives the period of the star. have periods of 3 to 50 days and can be seen for 60 million light years
period luminosity relation
transforms period into luminosity which is compared to a stars apparent brightness
Trigonometric parallex
using baseline of diameter of earths orbit to measure the distance of a star. parallex is the angle star appears to be moving using radius of earths orbit as the baseline
1 parsec
3.26 light years
Absolute magnitude
is the apparent magnitude it would appear to be at a hypothetical distance of 10 parsecs
a type II supernova
is the result of iron core collapse of a massive star
what ionizes the gas in a planetary nebula and makes it visible
ultraviolet photons emitted by a hot central star
a nova is the result of which explosive situation
mass transfer onto a white dwarf
astronomers use the term interstellar reddening to refer to
the scattering of starlight by dust grains in space
a type of star that has turned out to be extremely useful for measuring distances
cepheid variables
an iron core cannot support a massive main-sequence star because of what
iron cannot fuse to make heavier nuclei and produce energy
a white dwarf star has a diameter of approximately what
the earth
a type I supernova occurs when a white dwarf exceeds the mass of what
1.4 solar masses
a light curve for a star measures how its brightness changes with
time
what type of main sequence star is most likely to become a black hole
G star
what characteristic of a star cluster is used to determine its age
by comparing the main sequence turnoff in the clusters HR diagram to theoretical models
as a high-mass-main sequence star evolves off the main sequence it follow a
roughly horizontal path on the H-R diagram
an HII region
a zone around a hot star where hydrogen atoms are ionized
helium burns in the core of a horizontal branch star via __ and produces __
the triple-alpha reaction and carbon
what critical events have signaled that a star has reached the main-sequence
the fusion of Hydrogen in Helium begins in the core
the region around a black hole where everything is trapped and nothing can get out to interact with the rest of the universe
the even horizon
in a white dwarf, what is the source of pressure that halts its contraction as it cools
electrons packed so closely that they become degenerate
massive stars synthesize chemical elements going from helium up to what in the core
iron
which of the properties of a star typically requires a knowledge of distance before it can be determined
luminosity
essentially all the elements heavier than iron in our milky way were formed by what
supernovae or merging neutron stars
a young protostar with a mass of 1 solar masses as it evolves will move
vertically downward in the H-R diagram
when a star equal to the mass of the sun dies, it will become what?
a white dwarf
a type of cluster that contains really old stars
globular cluster
which stage of nuclear fusion is the last to occur in the core of a massive star
silicon fusion to iron
the path that a forming star follows as its position in the H-R diagram changes with time is called what
its evolutionary track
interstellar dust
seen as dark clouds silhouetted against a dark background
interstellar extinction
stars appear fainter
interstellar reddening
stars appear redder
molecular clouds
densest interstellar clouds whose temperature reach as low as 10K
star formation
results in UV radiation from O and B stars that ionize their immediate surroundings
surface temperature of protostar
remains constant while collapse is slowly taking place and core is heating up. star is shrinking and surface area is less and its luminosity is decreasing
main sequence turnoff
point on the main sequence where stars are just leaving the main sequence gives the age of the cluster
Low-mass stellar evolution
H fuel core of sun will be exhausted. He core collapses to a small radius. Dense and finds support from electron degeneracy (electrons cannot be pushed any closer)
Hydrogen shell burning
luminosity of star increases and outer region of star expands. becomes a subgiant and then a red giant
Helium core burning
Triple-alpha process. core temperature increases rapidly. star moves down onto He burning main sequence. now burning He in the core and H in the shell
Hydrogen and Helium shell burning
He is exhausted in the core it collapses again. Goes to second red giant branch lose large amounts of mass total of 30-50% of total mass
white dwarf
limit of 1.4M moves down to the left of the H-R diagram becomes the size of the earth after many years will become a black dwarf
Type Ia supernova
when a white dwarf exceeds 1.4M leftover iron and nickel shot out into space
Neutron star
core of supernova left behind maximum of 3M supported by electron degeneracy
pulsar
Electrons and Protons are caught in the magnetic field and beamed out in 2 narrow beams
black hole
mass of a core of a supernova exceeds 3M it collapses into a black hole
elliptical galaxies
E0 to E7 circular to elliptical shaped with their appearance depending upon their orientation. no star formation and no gas and dust
spiral galaxies
flattened rotating disks and spiral arms stars are forming
spiral arms
ongoing star formation locations of where clouds of interstellar gas is compressed
spiral density waves
spiral pattern associated with the disks rotation
Dark matter
90% of mass in a galaxy is dark matter
