Exam #3 Preview #2 & #3 combined
Suppose that the color and behavior of a star identify it as a type that we know has absolute magnitude -3. If the star is apparent magnitude is found to be 7, how far away is it?
1000 parsecs
Suppose that the color and behavior of a star identify it as a type that we know has absolute magnitude 4:8. If the star's apparent magnitude is found to be 14:8, how far away is it?
1000 parsecs
The violet lines in the Hydrogen spectrum are normally seen with wavelengths 410 nm and 434 nm. In the light of a star that is moving toward us, we might expect to see those lines at wavelengths of
20 years
The word 'Parallax' in the term 'Spectroscopic Parallax' is used because that term refers to
a method for finding distances to stars
The idea that a supernova is preceded by a huge burst of neutrinos is
a prediction that has now been observed
A star whose full spectral type is K2V is
a red main sequence star
In a particular binary star system, we are only able to determine a minimum mass for each star and cannot determine the angle between our line of sight and the plane of the starsíorbits. This system is most likely
a spectroscopic binary system
A pulsar is really a
a spinning neutron star
Stellar Parallax
can only be seen with a telescope
For stars on the main-sequence, stars with decreasing mass have
decreasing surface temperature and absolute brightness
Ham radio operators sometimes operate receivers for the 2 meter wavelength. The 2 meters refers to the
distance from one maximum of the radio waves to the next
Of all the things that might go wrong with distances found by using the method that astronmers refer to as the "distance ladder," which of these is the one that an astronomer would say is most likely?
distant objects are not behaving the same as nearby objects
The red subgiant stage of a star is best described by
dropping temperature and constant brightness
Which of the following particles has the smallest mass?
electron
The core of a red supergiant star stops shrinking because its
electrons touch each other
The point at which even an outwardly directed light ray is pulled into a black hole is called the
event horizon
Stars that are much more massive than our Sun
form faster and burn out faster
Stars that are much less massive than our Sun
form more slowly and burn slower
The origin of the energy that is released in a supernova explosion is
gravitational energy from the core collapse
When the temperature of a gas increases, its molecules
move faster
When a white dwarf star collects matter from a neighboring star, fusion reactions on the surface of the white dwarf cause
novas
A star with an absolute magnitude of 8.4 and an apparent magnitude of -1.0 would appear in our sky as a star
of dazzling brightness
On a Hertsprung-Russel diagram, stars that are burning Helium at their cores are found
on the Horizontal Branch
A converging lens will send the light from a distant star through a point
on the focal plane of the lens
The formation of a new white dwarf is usually accompanied by a
planetary nebula
In the Hertzsprung-Russell Diagram shown, which point represents a star of type B with absolute magnitude -5?
point E so on the highest left side where -5 is shown
A hydrogen atom with its electron removed (a H+ ion in other words) is actually a
proton
Neutron stars are often observed as
pulsars
Nuclear fusion requires high temperatures because nuclei
repel each other
A black hole that has formed from the collapse of a star is expected to be
similar in size to a neutron star
A star with an apparent magnitude of 8.4 and an absolute magnitude of -1.0 would appear in our sky as a star
that is visible only with a telescope
Which of the following magnitudes corresponds to the brightest star?
0
A star at a distance of 100pc should have an apparent brightness equal to its absolute brightness multiplied by
(10^ -2)
Which of the following magnitudes corresponds to the brightest star?
-1.5
The mass of a carbon atom is 12.00amu while the mass of a helium-4 atom is 4.003amu. If a gamma ray photon splits a carbon atom into three Helium atoms, how much energy is converted into mass?
0.009amu
The mass of a carbon atom is 12.00amu while the mass of a helium-4 atom is 4.003amu. If three atoms of helium fuse to form carbon, how much mass is converted into energy?
0.009amu
A star is seen to move by 0:4 seconds of arc between March 1, 1999 and September 1, 1999 and then back to its starting point on March 1, 2000. What is the parallax angle for this star?
0.2 seconds of arc
A star is seen to move by 0:8 seconds of arc between March 1, 1999 and September 1, 1999 and then back to its starting point on March 1, 2000. What is the parallax angle for this star?
0:4 seconds of arc
Barnardís star is a near neighbor of the Sun whose properties we know quite well. It is a type M4V with absolute magnitude 13.22. Suppose that another star of spectral type M4V is observed to have apparent magnitude 8.22. How far away is it?
1 parsec
Compared to a magnitude 16 star, a magnitude 1 star would be
1,000,000 times a bright
Cruising far from the Sun, we notice that the Sunís apparent brightness has dimmed to 10 watts per square meter. We know that the apparent brightness at a distance of 1au is 1000 watts per square meter. How far from the Sun are we?
10 au
A star with a distance modulus of zero is at a distance of
10 parsecs
A starship observes that a nearby star has apparent magnitude 4.0. The spectrum of the star indicates that it is a type that normally has absolute magnitude 4.0. From these observations, the starship knows that it is
10 parsecs from the star.
Cruising far from the Sun, we notice that the Sun's apparent brightness has dimmed to 0.1 watts per square meter. We know that the apparent brightness at a distance of 1au is 1000 watts per square meter. How far from the Sun were are?
100 au
A star at a distance of 10,000pc should have an apparent brightness equal to its absolute brightness multiplied by
10^6
Suppose that a sound wave has a wavelength of 12 meters and a frequency of 100Hz. What is the speed of sound?
1200 m/s
Suppose that a flash of lightning from a cloud 2500 meters away is followed by a clap of thunder two seconds later. Assume that the light arrived in a negligible time and calculate the speed of the sound waves.
1250m/s
A star whose apparent brightness is 104 times that of a sixth magnitude star would have magnitude
16
The velocity of sound waves is roughly the same for all wavelengths. Suppose that a sound wave has a wavelength of one meter and a frequency of 1000Hz. The wavelength of a 250Hz sound wave would then be
4 m
The violet lines in the Hydrogen spectrum are normally seen with wavelengths 410 nm and 434 nm. In the light of a star that is moving toward us, we might expect to see those lines at wavelengths of
400 nm and 424 nm
You hear a 1000Hz tone from a radio that is 20 feet away from you and listen for 5 seconds. How many pressure maxima pass by your ear?
5000
Suppose that you want to double all of the dimensions of a telescope that uses a large lens to collect light. The amount of glass that you need to form the lens of the new, twice as large, telescope is
8 times the amount needed for the original telescope
Epsilon Eridani shows a proper motion of 0.97661 arc seconds per year. In 100 years, its position in the sky changes by
97.661 seconds of arc
Which of the following spectral classes corresponds to the second highest surface temperature (on this list)?
A
The period of a photo-star's evolution when its size and brightness decrease just before the ignition of nuclear reactions in its core is called
The Tau Tauri Phase
In the Hertzsprung-Russell Diagram shown, which point represents a star of type F with absolute magnitude -5?
C
Which of these answers describes the fundamental assumption that is behind all of the methods that astronomers refer to as the "distance ladder?"
Distant objects are similar to nearby objects
Which of the following spectral types corresponds to the star with the highest surface temperature?
F0
Which of the following spectral types corresponds to a star on the main sequence?
G2V
High protostellar winds of ejected gas occur when the protostar is in the
Tau Tauri phase
The star Wemadeit shows a stellar parallax angle of 0.2 seconds of arc while the star Waytoofar shows a stellar parallax angle of 0.3 seconds of arc. From this, you can conclude that
Waytoofar is closer to our Sun than Wemadeit
The star Wemadeit shows a stellar parallax angle of 0.3 seconds of arc while the star Waytoofar shows a stellar parallax angle of 0.2 seconds of arc. From this, you can conclude that
Wemadeit is closer to our Sun than Waytoofar
The object Gliese 229B glows in the infrared but is much cooler and dimmer than a class M star and shows traces of lithium that a normal star would quickly burn up in the nuclear reaction that occurs in its core. This object is most likely
a brown dwarf
We see what appears to be a single star. However, when the light from the star is put through a spectrometer, we see two distinct spectra, shifting back and forth. The star is actually
a double-line spectroscopic binary system
A type Ia supernova occurs when
a white-dwarf begins to collapse
The first red giant stage of a one solar-mass star's life usually ends with
an explosion in the helium core
The Örst red giant stage of a one solar mass starís life usually ends with
an explosion in the helium core
In a Hertzsprung-Russell diagram,white dwarf stars such as Sirius B are
at the lower left
In a Hertzsprung-Rusell Diagram, the brightest stars are found
at the top
Adaptive optics is used to correct telescopes for
atmospheric turbulence
A star that forms an iron core most likely has a mass of
between 15 and 20 solar masses
A main-sequence star with more mass than our sun will be .....
hotter and brighter
In the Hertzsprung-Russell Diagram, a main sequence star would not be found
in the upper right or lower left
Stars with more than 15 times the mass of our Sun usually evolve o§ the main sequence along a path in the HR diagram that
is mostly horizontal
Suppose that a star has a spectrum that includes red, blue, and violet lines spaced in the pattern of the lines from hydrogen but the violet lines are at 444nm and 420nm instead of the usual 434nm and 410nm. From this evidence, you can conclude that the star is
moving away from us
A spectroscopic binary star system is one in which we see
spectral lines shifting back and forth
Once a star has evolved onto the Main Sequence in the HR Diagram, it
stays at the same point until it runs out of fuel
Think of the 'front' of a telescope as the end that light enters. A telescope with Newtonian Focus has the eyepiece
sticking out the side near the front
Think of the ëfrontíof a telescope as the end that light enters. A telescope with Newtonian Focus has the eyepiece
sticking out the side near the front
When the hydrogen fuel runs out at the center of a main sequence star, the star
swells up and becomes a red giant
The average energy of motion of an atom or molecule in a gas is called its
temperature
The velocity of a wave is deÖned to be
the distance traveled by a crest divided by the time taken
The Örst red giant phase of a star is caused by
the exhaustion of hydrogen @ its core
For an eclipsing spectroscopic binary star system, we can determine
the masses and diameters of both stars in the system
Stellar Parallax is caused by
the motion of the Earth around the Sun
The position of a protostar on an HR diagram changes because
the size and temperature of the protostar change
In order to use spectroscopic parallax to Önd the distance to a star, you need to know
the spectral type and luminosity class (B2V for example) and the apparent magnitude
The diffraction limit of a telescope refers to the effect of
the wavelength of light
The distraction limit of a telescope refers to the e§ect of
the wavelength of light
Because mirrors only use one surface, they have a big advantage over lenses: They can be
thinner and larger in diameter
When the core of a star collapses while inside the star, the result is a
type II supernova
A mirror that is shaped like a shallow bowl sitting on the table with its open end facing up will focus light that comes
vertically down from above
A star that is 10,000 miles in diameter is probably a
white dwarf star
A star that is approximately the size of the Earth is probably a
white dwarf star