FINAL EXAM Flashcards
Imagine a line going through Earth, connecting the North and
South Poles. Earth rotates about
this line.
Earths Axis
If we extend the Earth’s axis what are the points where it connects with the celestial sphere?
North & South celestial pole
the equator of the celestial sphere is called the
Ecliptic
Planetary orbits are ellipses, with the Sun at one focus
Keplers First Law
path of an object
through space
orbit
one of the two
foci
focus
The imaginary line connecting Sun and planet sweeps out
equal areas in equal times.
Keplers Second Law
the speed of an orbiting planet (or moon or satellite) will change depending where it is in the orbit is called what
consequence
Square of period of planet’s orbital motion is proportional to cube of semi-major axis.
Keplers Third Law
the time it takes a
planet to travel once around
the Sun
Period
the average distance between
Earth and the Sun
1 AU
an excitation that propagates through space or a medium
wave
sound waves, water waves governed by Newton’s laws exist with a medium
Mechanical waves
light, radio waves, microwaves can travel in a vacuum (don’t need a medium to propagate) travel with velocity c = 2.99x108 m/s, which is the speed of light
Electromagnetic waves
maximum departure of a wave from the undisturbed state
Amplitude
number of meters needed for the wave to repeat itself at a given
moment in time
Wavelength
number of seconds needed for a wave to repeat itself at some point
in space
period
number of crests passing a given point per unit time
frequency
frequency = ?
1 / Period
The energy ux from a blackbody at temperature T is proportional to the
fourth power of its absolute temperature. This relationship is known as the
Stefan-Boltzmann law
The location of the spectral peak (or maximum) in the power curve of each star
can tell us its temperature
Wiens Law
______ allow us to collect
the radiation and focus it on
detectors where we can store
and analyze it
Telescopes
Types of telescopes
Radio, Infrared, optical, UV, x-ray, gamma rays
____ needs two optically acceptable surfaces, _____ only needs one: easier to make mirrors
Lens; Mirror
_______’s use mirrors or lenses to collect light
Optical Telescopes
Because this array of colors is a spectrum of light, the instrument used to
disperse the light and form the spectrum is called a
spectrometer
____ is the building block of all matter
atom
Surrounding the nucleus, there are ____ negatively charged
electrons
_______ are due to the discrete (quantum) spacing of an atom’s electron
energy levels
spectral lines
What event emits a photon of a discrete energy equal to the difference of the energy levels
Electron de-excites
an array of all wavelengths or colors of the
rainbow.
Continuous spectrum
appears as a pattern or series of bright lines; it consists of light in which only certain discrete wavelengths are present
emission spectrum
If a continuous spectrum passes through a
cool gas, atoms of the gas will absorb the same frequencies they emit
when excited describes what?
Absorption Spectrum
From sun (source of continuous spectrum) to a cloud of gas with few absorption lines results in _____. From cloud of gas with predominantly absorption lines results in ___. Straight from sun to _____ spectrum with no absorption lines
Absorption spectrum, emission spectrum, continuous spectrum
To measure stellar parallax use position of Earth in January (A)/July(B)
Parsec
Referring to parsecs: d (distance) =
s / angle
d(parsec) =
1 / (angle * arcseconds)
The magnitude equation is:
apparent magnitude - absolute magnitude = 5log(distance / (10pc)
What is the difference between apparent and absolute magnitude of a star 100 pc away?
5
A star has an apparent magnitude 10.0 and an absolute magnitude 2.5.
How far away is it?
316pc
Name the categories of stellar spectra:
O B A F G K M (Oh Be A Funny Goat, Kick Me)
Intrinsic Variable Stars Used for Distance are _____ & ________
Cepheid & RR Lyrae stars
____ stars have
essentially the same luminosity curve, with
periods from 0.5 to 1 day.
RR Lyrae
________ periods range from about 1 to 100
days.
Cepheid Variables
______ all have about the same
luminosity; knowing their apparent
magnitude allows us to calculate the
distance
RR Lyrae Stars
______ have a luminosity that is
strongly correlated with the period of
their oscillations; once the period is
measured, the luminosity is known and
we can proceed as above
Cepheids
___ gas is found in Emission
nebulae: hot, glowing area associated with the
formation of large stars.
ionized hydrogen(H*)
Found in cold regions
without stars between dust clouds
atomic hydrogen(H)
Found in cold dark
dust clouds
Molecular hydrogen(H2)
______ are composed of atomic
hydrogen gas that is ionized by near-by stars and are located in which region
emission nebulae; HII
____ plots stellar luminosity versus surface temperature
HR Diagram
This region is
where star formation occurs
molecular hydrogen
The darkened curve on the HR Diagram is called the ____, as this is where most stars are
Main sequence
these stars are hot but not very luminous, as they are quite small
White Dwarfs
the brightest stars in the sky appear bright because of their
enormous luminosities and not their proximity
____ giants are toward the start of the main sequence
blue
____ giants are above the end of the main sequence
red
____ percent of stars lie on
the main sequence
90
___ percent of stars are red giants
9
___ percent of stars are white dwarves
1
_____ lie under the main sequence
White dwarfs
On the HR diagram, The shape of the paths is similar, but they wind up in
different places on the main
sequence depending on their
Mass
____ causes a star to burn hydrogen in the surrounding shell.The core contracts and heats; the outer atmosphere expands and cools.
Once hydrogen is gone
Helium begins to fuse in the core & The star expands into a red giant as the core
continues to collapse describes what
Helium Flash
Only stars with a end life mass of less than 1.4 times the mass of the Sun (called
_____________) will end their cycle as white dwarfs
Chandrasekhar limit
The collapsing core can reach a stable state as a crushed ball made mainly of neutrons, which astronomers call a
neutron star
loose, irregular cluster, found mainly
in the plane of the Milky Way
open cluster
spherical cluster of stars with the
absence of massive main-sequence stars, and the heavily
populated red giant region. Found away from the galactic
plane.
globular cluster
________ Galaxies - no spiral arms and no disk
Elliptical
____ galaxies show various degrees of flattening, ranging from systems that
are approximately spherical to those that approach the flatness of spirals.
Elliptical
Star classification that have a disk and bulge, but no spiral arms, no interstellar gas. In between
ellipticals and spirals.
SB & SBO
______ galaxies have a wide variety of shapes. Undergoing interactions with other galaxies.
Irregular
very powerful and compact sources of energy at the centers of distant galaxies
quasar
_____ type galaxies are generally elliptical and lenticular (S0) galaxies
Early
____ type galaxies are spiral and irregular galaxies
late
Name the equation: v = H * d
Hubbles Law
Age of the Universe of about
13.8 billion years
Name the principle: the Universe is both homogeneous and isotropic
Cosmological
The fate of the universe (the old theory)
slow expansion or decelerate back to the beginning
The fate of the universe (the new theory)
The universe is expanding rapidly due to dark energy
Arno Penzias and Robert Wilson observed the big bang known as the
Cosmic background Radiation
____ percent of stuff in the universe is made of dark matter and dark energy
95
The reciprocal of the Hubble constant (1/H) is a rough measure of the
age of the universe
T OR F: If the expansion of the universe were accelerating, it would mean that distant Type Ia supernovae would look fainter than we would expect from measuring their redshifts and applying Hubble’s law.
True
T OR F: As the universe expands, the temperature throughout the universe increases regularly
False
T OR F: All the evidence currently suggests that we live in closed universe
False
T OR F: The latest conclusion that astronomers have reached about the expansion of the universe is that the rate at which space is expanding is decelerating – that is, the expansion is slowing down due to the pull of gravity.
False
Recent observations indicate that the universe is expanding faster today than it was a few billion years ago (that, in other words, the expansion of the universe is accelerating.) What kind of observations have led astronomers to this surprising conclusion?
the measurement of galaxy distances using white dwarf (type Ia) supernovae
According to the Cosmological Principle, the universe is _____ & ______
isotropic and homogeneous
Roughly how many galaxies make up our Local Group?
About 60 or so
What cluster is Earth located in
Virgo Supercluster
Which type of galaxy is observed to contain mostly older stars?
Elliptical
In which type of galaxy are you likely to observe a significant amount of star formation?
Spiral irregular
Hubbles constant is around ____ kilometers a second
70
Our Milky Way Galaxy is what type of galaxy?
spiral
The type of galaxy that consists almost entirely of old stars and is thus less blue (more yellow and reddish) than the other types is:
elliptical
Edwin Hubble developed a classification scheme for galaxies. By what characteristic did he classify galaxies?
their shape
Today, astronomers find compelling evidence that the energy source of the quasars and active galaxies is
matter falling toward a supermassive black hole at the center of a galaxy
Which of the following objects is considered useful to astronomers as a “standard candle” for determining distances?
White dwarf
Edwin Hubble was able to show that (with the exception of our nearest neighbors) the farther a galaxy is from us, the
faster it is moving away from us
To calculate the redshift (𝑧) of the quasar, we can use the following formula for redshift:
(observed - rest) / rest
When a quasar is moving away from us at a significant fraction of the speed of light, we can use the relativistic redshift formula to calculate the redshift (𝑧):
sqrt((1+B) / (1-B)) - 1
(B = v/c)
gas and dust that lie between stars
interstellar matter
reflection nebulae have a ____ cast as their interstellar dust grains preferentially reflect _____ starlight (Hint: answer is a color)
Blue
a zone around a hot star where hydrogen atoms are ionized
HII Region
The red color we see on a lot of photographs of nebulae comes from which element?
hydrogen
Which of the following types of star is the coolest (has the lowest surface temperature)?
M
How to calculate parallax
d = 1 / p (parallax angle)
T OR F: The amount by which the spectral lines of a star is redshifted tells astronomers how fast the star is moving away from us.
True
The formula relating distance, apparent brightness (also called flux), and luminosity is
apparent brightness = luminosity / (4π * distance^2)
which planets revolve around the Sun in the same direction
All of them
T OR F: jovian planets (being larger) rotate significantly more slowly than terrestrials
FALSE
what do all four terrestrial planets have in common?
they all have solid surfaces with signs of geological activity on them
The region around the Earth where charged particles are trapped and spiral around is called the ____ sphere
magneto
T OR F: a comet always has a nice long tail, even when it is far from the Sun
FALSE
what wave has the longest wavelength?
radio waves
T OR F: For all electromagnetic waves, the frequency multiplied by the wavelength will be the same constant number.
FALSE
Which ancient Greek thinker suggested (long before Copernicus) that the Earth is moving around the Sun?
Aristarchus
T OR F: At the Earth’s equator, you would see the celestial poles on your horizon.
TRUE
A star is 230 light-years away. The light we see tonight from that star left it
230 years ago
The point in the sky directly above your head at any given time is called the
zenith
T OR F: The path that the Sun appears to make in the sky over the course of a year is called the celestial equator.
FALSE
The scientist who first devised experimental tests to demonstrate the validity of the heliocentric model of the solar system was
Galileo
