Astronomy Exam 4 (Ch 12-16)
Stellar Parallax
can only be seen with a telescope.
On the present Earth, the portable source of carbon that plants use to build complex organic compounds is
carbon dioxide.
The oxygen atom in a water molecule
carries a negative electrical charge.
As of July, 2018, The number of confirmed exoplanets found by the transit photometry method was closest to
2500.
The star π³-Orionis is 8 parsecs from our Sun. The light from π³-Orionis has been traveling for
26.4 years.
The star Kruger 60 shows a heliocentric stellar parallax of almost exactly 0.25 seconds of arc. The distance from our Sun to Kruger 60 is
4 parsecs.
Our own Sun has an absolute visual magnitude of 4.8. A starship that travels 10 parsecs from our Sun and looks back at the Sun will see it as having apparent visual magnitude
4.8.
One difficulty with the microfossils that were found in the martian meteorite ALH84001 is that they
are too small.
Which of these moons has landmarks that are not rotating with the rest of the moon, indicating a subsurface ocean?
Titan.
The eclipse or transit photometry method of searching for exoplanets can be expected to find
less than one out of every 10 exoplanets.
A converging lens will send the light from a distant star through a point
on the side of the lens opposite the star.
Oxygen is
one of the four most common elements in the universe.
Most plants here on Earth are green because the process of converting carbon dioxide and water into organic matter uses only
red, blue, and violet light.
To see small but bright objects such as the ice caps on Mars, you would need a telescope with large
resolving power.
In SETI programs, the "water hole" refers to
the range of signal frequencies between emissions caused by hydrogen and hydroxyl molecules.
The diffraction limit of a telescope refers to the effect of
the wavelength of light.
If we wish to find life with a carbon-return process similar to the one here on Earth, we should look for planets
with thin, unstable surfaces.
Which of these is a statement of the Fermi Paradox?
Any long-lasting technological civilization should be obvious and might even be visiting us, so where are they?
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 systems do most living things on Earth now use to reproduce themselves?
Each DNA molecules splits in half and each half acts as a pattern to complete its other half.
Which of these moons has patterns of cracks in the ice on its surface. indicating a subsurface ocean?
Europa.
14.1-2 Which of the following spectral classes corresponds to the second lowest surface temperature (on this list)?
G
What astronomers refer to as a "standard candle" is defined as a light source whose
absolute magnitude is known.
The strongest evidence that Earth life is all descended from a single self-copying molecule is that all Earth life
contains the same version of molecules that have different mirror-image forms.
Current computer models of planet formation suggest that the Alpha Centauri system
could have planets within the habitable zones of both Alpha Centauri A and Alpha Centauri B.
Which of the following types of radiation has the second lowest frequency on this list? a ultraviolet light. b green light. c infrared light. d X-rays. e red light.
e. red light.
The primary mission of the Kepler Spacecraft is to
find planets in orbit around nearby stars.
A spectrum is defined to be the set of
frequencies or colors present in a light source.
Which of the following types of radiation has the second lowest frequency on this list? a red light. b infrared light. c green light. d X-rays. e heat radiation.
infrared light.
When water freezes, the resulting ice occupies
more volume than the liquid water did.
Complex hydrocarbons such as sugars are found
on Earth and in interstellar clouds.
The role of the DNA molecule in current Earth life is to
provide the patterns for the enzymes that carry out the chemical processes of life.
A star that is cooler than most other stars will probably look
red.
Which of the following magnitudes corresponds to the brightest star? a +3.4. b +5.6. c +2.1. d -1.5. e +1.2
-1.5.
Which of the following magnitudes corresponds to the brightest star?
-4.2
A star is seen to move by 0.2 seconds of arc between February 1, 1999 and August 1, 1999 and then back to its starting point on February 1, 2000. What is the parallax angle for this star?
0.1 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.
The apparent brightness of our Sun is roughly 1000 watts per square meter. At a distance of 30 times the Earth-Sun distance, the apparent brightness of our Sun would be
1.1 watts per square meter.
The star Tau Ceti has moved across the sky by 1922 seconds of arc during the last thousand years, more than a half of a degree of arc. Its proper motion is closest to
1.9265′′/yr.
Cruising far from the Sun, we notice that the Sun's 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.
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 9.8, how far away is it?
100 parsecs
A star is observed to have an apparent brightness which is 10⁻² times its absolute brightness. How far away is it?
100 parsecs.
Compared to a magnitude 6 star, a magnitude 1 star would be
100 times as bright.
A star is found to have absolute magnitude 4 and apparent magnitude 24. How far away is it?
100,000 parsecs
A star is found to have absolute magnitude -1 and apparent magnitude 19. How far away is it?
100,000 parsecs.
Suppose that the color and behavior of a star identify it as a type that we know has absolute magnitude --3. If the star's apparent magnitude is found to be 7, how far away is it?
1000 parsecs.
Barnard's star shows a proper motion of 10.36 arc seconds per year. In 100 years, its position in the sky changes by
1036 seconds of arc.
The star 61-Cygni is 3.3 parsecs from our Sun. The light from this star in the "serpent holder" constellation has been traveling for approximately
11 years.
Suppose that a sound wave has a wavelength of 12 meters and a frequency of 1Hz. What is the speed of sound?
12 m/s
A star whose apparent brightness is 10⁻⁶ times that of a first magnitude star would have magnitude
16.
The star epsilon-Eridani shows a heliocentric stellar parallax near 1/3 seconds of arc. The distance from our Sun to epsilon-Eridani is near
3 parsecs.
Compared to the frequency of photons absorbed during a transition from a -5ev state to a -4ev state, transitions from the -5ev state to a -2ev state would correspond to absorbing photons whose frequency is
3 times as high.
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
Compared to the frequency of photons absorbed during a transition from a -6ev state to a -5ev state, transitions from the -6ev state to a -1ev state would correspond to absorbing photons whose frequency is
5 times as high.
You hear a 1000Hz tone from a radio that is 10 feet away from you and listen for 5 seconds. How many pressure maxima pass by your ear?
5000.
The red line of a spectrum is normally at a wavelength of 656 nm. In the light of a star that is moving away from us, we might expect to see that red line at a wavelength of
660 nm
Which of the following discoveries would lead to the conclusion that the universe is probably filled with life, both in our own solar system, and in the planetary systems of other stars?
A few microbes with a completely alien biochemistry are found beneath the soil of Mars.
Which of the following requirements for life appears to lacking on the planet Mars?
A global carbon-return process.
If we should find micro-organisms on Mars that reproduce using a DNA/RNA scheme and set of amino acids that are mirror images of those used in all Earth life-forms, that would support the
Abiogenesis Model.
A multiple star system close to the Earth that is known to have stable orbits in the habitable zones of each of its stars is
Alpha Centauri.
The closest star to Earth (other than the Sun) is part of a multiple star system called
Alpha Centauri.
Which of the following statements best describes the presence of water on Mars?
Mars has water frozen in its ice caps and may have liquid water below its surface.
You see a telescope with a long tube and the eyepiece sticking out the side near the top. This telescope uses the
Newtonian Focus.
The search for extrasolar planets has started to find "super-Earths," planets several times as large as Earth but with about the same density. From what we understand so far about plate tectonics on Earth, how likely is it that these super-Earths would have active surfaces like ours?
Possible if other conditions are also present.
A single sugar phosphate chain with nitrogenous bases attached along it describes a molecule of
RNA.
Which of the following features in the light reflected from a planet would indicate the presence of Earth-type plants (rather than just colored rocks) on its surface?
Red light is not reflected, but infra-red light is strongly reflected.
Which of the following models for the formation of life on Earth would most likely apply if it turns out that the first step of forming a self-copying molecule is extremely difficult and improbable?
The Panspermia Model.
Suppose that some very strange creatures are found in a long-isolated place such as underneath the ice of Antarctica. Which of the following would be the strongest evidence that these creatures are descended from a different `first replicating molecule' than the rest of life on Earth?
The creatures use amino acid molecules that are mirror-images of the usual ones.
The Viking Landers carried out several experiments on Martian surface soil. The final conclusion from those experiments (as interpreted at the time) was:
The surface of Mars is extremely hostile to all forms of organic matter.
Which of these moons could have two levels of oceans, with oceans of liquid hydrocarbons on the surface and oceans of liquid water beneath the surface?
Titan.
An inventor proposes to generate electrical energy by hooking an electric generator to a water wheel. The water wheel takes water stored in a reservoir behind a dam and lowers it to the level of the water at the foot of the dam. Unfortunately there is a drought and the reservoir is drying up. To solve this problem, the inventor proposes to use the electricity from his generator to run a pump that takes water from the foot of the dam and puts it back up into the reservoir. Assume that he manages to eliminate all energy-wasting effects such as friction.
This idea will fail because it takes exactly the same amount of energy to raise the water up as it releases when it comes down. The scheme will not generate energy for other uses.
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 0.4 seconds of arc. From this, you can conclude that
Waytoofar is closer to our Sun than Wemadeit.
Astronomers find a single star image whose spectrum shows lines that shift back and forth with a regular period and whose intensity shows dips that repeat with the same period. They have found
a binary system in which they can determine the mass and diameter of each star.
Civilizations capable of sending out broadcast messages that we could possibly detect across interstellar distances would have to be technologically advanced and would probably be much more advanced than we are. That makes it difficult to decide what sort of signals they would send. The SETI program has decided to listen for microwave signals rather than more exotic types of signals (such as laser light, gamma rays, neutrinos, gravitational waves, etc.). The main reason for this choice is that
a microwave signal can send the largest amount of information for a given amount of energy used to generate the signal.
We see what appears to be a single star. However, when the light from the star is put through a spectrometer, we see that its spectrum is shifting back and forth. The star is most likely
a single-line spectroscopic binary system.
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 stars' orbits. This system is most likely
a spectroscopic binary system.
When the light from a star is spread out into a rainbow of colors, the resulting picture is called
a spectrum.
An example of a life form that does not get its energy originally from the Sun would be
a tube worm near a black smoker.
In a particular binary star system, we are able to determine the masses of both stars in the system as well as the angle between our line of sight and the plane of the stars' orbits but cannot determine the diameters or atmospheric compositions of the two stars. This system is most likely
a visual binary system.
In a particular binary star system, we are able to determine the masses and diameters of both stars This system is most likely
an eclipsing spectroscopic binary system.
Adaptive optics is used to correct telescopes for
atmospheric turbulence.
A necessary (but probably not sufficient) condition for a planet to have active plate tectonics is that it
be considerably larger than the planet Mars.
The main reason to suspect that Enceladus has a subsurface ocean of water is
geysers of water shooting out through cracks in the moon.
The range of distances of a planet from its primary star that will permit the existence of liquid water on the planet's surface is called the
habitable zone.
A converging mirror of the sort that is used to collect light in astronomical telescopes
has a focal point on the same side of the mirror as the light source.
The molecules of both water ice and liquid water are attached to one another by
hydrogen bonds --- .Different parts of each molecule have opposite charges.
The molecules of both liquid water and ice are held together by
hydrogen bonds.
The most common element in the universe is
hydrogen.
If there is life on one of the Jovian moons, we would expect that life to most likely be
in the subsurface oceans, using chemical and thermal energy.
If the frequency of electromagnetic radiation goes from 4×10¹⁴Hz to 2×10¹⁴Hz, the energy of each individual photon in the radiation
is divided by 2.
If the frequency of electromagnetic radiation goes from 2×10¹⁴Hz to 6×10¹⁴Hz, the energy of each individual photon in the radiation
is multiplied by 3.
A planet larger than Mars would be a good place to look for life because
it might retain enough interior heat to drive plate tectonics.
The star Gliese 581 is of particular interest mainly because it is
known to have three terrestrial-size planets near or in its habitable zone.
As compared to higher frequency electromagnetic radiation, lower frequency electromagnetic radiation will usually cause
less damage.
Ultraviolet light is sometimes described as either UV-A or UV-B. The UV-A variety is supposed to be less damaging to your skin. You can conclude that of the two types, the UV-A variety has the
lower frequency.
The reason that most SETI programs choose to listen at microwave radio frequencies is that
microwaves are the most energy efficient way to send information.
Because different molecules vibrate with distinctive radio frequencies, it is possible for radio telescopes to identify the chemical compounds that are present in interstellar clouds. When they look for complex compounds (more than four atoms) they find
mostly carbon compounds.
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.
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 red line is has a wavelength of 650 nm instead of the usual 656 nm. From this evidence, you can conclude that the star is
moving toward us.
According to the definition of "habitable zone" that we are using, Earth is
near the inner edge of the habitable zone of our Solar System.
The Viking Landers carried out several experiments on Martian surface soil. One of those experiments, the Pyrolytic Release Experiment gave a positive result for the presence of life forms. That result was interpreted to mean
nothing because a sterilized control sample gave the same result.
Here is the Drake Equation. In this equation, N stands for the
number of communication-capable civilizations in our galaxy.
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.
The wavelength of the sound waves that correspond to middle-C is about 4 feet. If you are standing 4 feet away from a piano that is playing that note, then between you and the piano there will usually be
one region of maximum pressure.
Black holes are often discovered by observing the shifting of spectral lines in an ordinary star that they are orbiting. Careful measurements of the shifting spectral lines can provide
only a minimum mass for the black hole.
Silicon atoms can bond to other silicon atoms to form polysilylene molecules in much the same way that carbon atoms can bond to other carbon atoms to form sugars and other hydrocarbon molecules. What is the key difficulty with basing life on silicon and polysilylenes instead of on carbon compounds such as glucose?
polysilylenes tend to explode in the presence of oxygen.
Planets that are in orbit around stars other than our own Sun are more often found by observing
small wobbles in their primary stars.
A spectroscopic binary star system is one in which we see
spectral lines shifting back and forth.
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.
Green plants obtain the energy they need from
sunlight.
A star with an apparent magnitude of 5.7 and an absolute magnitude of -1.2 would appear in our sky as a star
that is barely visible to the naked eye.
The wavelength of a wave is defined to be
the distance from one crest to the next.
The velocity of a wave is defined to be
the distance traveled by a crest divided by the time taken.
A hydrogen bond is the result of
the electrical attraction between a hydrogen atom on one molecule and an oppositely charged part of another molecule.
We can see the star Sirius and its companion, the Pup, moving around each other. Careful measurement of this motion can provide
the masses of both stars in the system.
If we detect that the intensity of the light from a star is mostly constant but drops slightly to a new constant value for a while and then returns to its normal level and repeats this behavior at regular intervals, we can reasonably suspect that
the star has a planet in orbit around it.
The main reason that the SETI@home system needs to use the computing power of 5.2 million participating home computers is that
they are collecting and analyzing signals on millions of different radio channels.
Because mirrors only use one surface, they have a big advantage over lenses: They can be
thinner and larger in diameter.
The two hydrogen atoms in a water molecule are both attached
to the oxygen atom, but offset so that the molecule looks bent.
Our Sun's nearest neighbor star system is
two stars in close orbit around each other and a third star orbiting farther out.
A DNA molecule consists of
two sugar phosphate chains connected by pairs of nitrogenous bases.
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.
