Astronomy Exam #2

This NASA image shows the first five planet discoveries of the Kepler mission, as well as all known exoplanets in the universe. Based on their size and orbital distance, the Kepler exoplanets are most likely which kind of planet?

hot Jupiters

At the densities of the Sun, hydrogen nuclear fusion can occur at temperatures greater than about 10 million degrees Kelvin (K).Based on these graphs of the Sun's pressure, density, and temperature in its interior, where are the nuclear reactions occurring?

in a central region 20% the size of the entire Sun

The energy that is emitted from the Sun is produced:

in the core, by nuclear fusion.

As frequency increases, the energy of a photon _________ and its wavelength __________.

increases; decreases

The first reported extrasolar planet was discovered in ______ and was called __________.

1995; 51 Pegasi b

What nuclei are produced? (If there are multiple nuclei that are the same, only select it once.)

1H, 4He

What is the speed of light in a vacuum?

300,000 km/s.

What nuclei enter the final collision? (If there are multiple nuclei that are the same, only select it once.)

3He

The Jason telescope has a focal length for the objective of 700 mm, an objective diameter of 60 mm, and it is advertised to have a maximum magnification of 155. Approximately what must the focal length of the eyepiece be that they include with this scope to produce that magnification?

4.5 mm

A black body radiates at 6,000 Kelvin. The peak of this black body curve (𝜆max) will occur at what wavelength?

483 nm

If we discovered a 4th planet around 51 Pegasi what would it be called? (*You may have to do a little research on the naming convention of exoplanets to answer this.)

51 Pegasi e

According to the video how many potential exoplanets had been detected by the Kepler space telescope in the first 15 months?

700

According to figure 5.25 in your text most exoplanets discovered as of 2016 are are comparable in size to which planet in our solar system?

Neptune

Which black body curve represents the hottest object?

Curve A

Which black body curve would be representative of the Sun and what color would the light be?

Curve A; white

Which black body curve represents the reddest object?

Curve C

According to the video, which method of extrasolar planet discovery is the one that provides us with information on the planet's mass?

Doppler Effect

The first extrasolar planets discovered were found by which method?

Doppler Effect

The nature of light is rather unique: It acts like both a particle (called a photon) and a wave that can propagate energy even through empty space. Navigate to the interactive figure in Section 2 of this animation, as shown below, to see how changing the amplitude, wavelength, speed, and frequency of a light wave affects its properties. Choose all of the effects that would automatically happen if the wavelength of light were increased.

E.The energy of the light would decrease. F.The frequency of the light would decrease.

The Sun's interior is extremely dense, so as soon as a photon is produced inside the Sun, it is almost instantly absorbed by matter. It is then emitted in a random direction and possibly at a different wavelength, only to be absorbed again and reemitted. This results in a random walk of the photons as they move toward the surface, where they can escape into space. This situation may sound familiar: it is the effect of a blackbody, which is similar to the simplified view of light bouncing around in a box until it is able to randomly escape from a tiny hole, as shown in the figure. Say you are trying to study the nuclear reactions in the Sun's core by observing photons coming off its surface. How will this random walk affect your results?

Each photon would have been created a long time ago: it would be impossible to use them to study nuclear reactions as they are happening right now in the Sun's interior. Each photon may be a different color than it was when it was created in the nuclear reactions. Each photon may be a different energy than it was when it was created in the nuclear reactions.

The gas tube demonstrated in class produced what kind of spectrum?

Emission

A signal sent to the nearest star will get there faster if sent by gamma rays rather than radio waves.

False

The hot jupiters that have been discovered that have orbits close to their host stars also must have formed in that close proximity.

False

In the video Geoff Marcy is setting up to observe a star (Kepler 22) using the Keck telescope in Hawaii. Geoff video links from California and the telescope operator comments on the seeing at the observatory. What was the measurement of this seeing and is this a good value?

0.85 arcseconds; it's excellent!

Put the following stages of planet formation in order of occurrence.

1. An interstellar cloud collapses into a disk of gas, dust. 2. Gas pushes smaller dust grains into larger grains. 3. Larger dust grains grow into clumps 4. Clumps of dust collide and stick, forming planetesimals. 5. Km-sized planetesimals attract other objects by gravity. 6. Planets of various sizes form

Changing the wavelength of visible light changes its color. If the wavelength is decreased or increased outside of the range of wavelengths our eyes can detect, the light becomes invisible to us, but it is still fundamentally light. Examine the figure, which shows the entire electromagnetic spectrum and includes all types of light as a function of wavelength. Given what you learned from the figure, rank these types of light in order of increasing energy.

1. Radio 2. Infrared 3. Orange 4. Green 5. Ultraviolet 6. Gamma ray

Geoff Marcy is actually taking spectroscopic measurements of Kepler 22 in order to measure the "wobble" of the star due to its orbit around the system's common center of gravity and he describes it as the gravitational pull from the planet Kepler 22b. This wobble produces a Doppler shift, which gives the radial velocity of the star at the moment of the observation. What was the precision of his velocity measurements as quoted in the video?

1.5 m/s

A new star is forming inside this glowing cloud of gas. The dark band in the middle is made of a disk of thick dust, which obscures the light within it and hides the forming star from view. Newly forming stars are surrounded by gas and dust. Based on this observation--and your previous observations about the relative orbits, positions, and sizes of the planets--what is the most likely scenario for the formation of the Solar System?

A cloud of gas and dust collapsed into a flattened disk, within which the Sun and planets formed.

Comparing objects in a related group can reveal patterns among them. These patterns in turn can help us learn more about those objects than we could by studying each individually.With this goal in mind, watch the Introduction of the AstroTour Animation on Solar System Formation. Pay attention to the animation of the planets in the Solar System and select all of the following choices that describe the patterns that you've observed. As you do so, think about the implications of how the Solar System may have formed

All planets orbit the Sun in a roughly flat plane. All planets orbit the Sun in the same direction. The orbits of the outer planets (those most distant from the Sun) are spaced farther apart from one another than the orbits of the inner planets. The closest planets to the Sun are much smaller than the planets that are farther away.

Following the invention of the telescope, astronomers were able to measure the speed of light by observing Jupiter's moons passing behind Jupiter in their orbit and becoming eclipsed. Study the figure, which shows how someone on Earth can view Jupiter's moon's eclipses when Earth is closer to or farther from Jupiter, and determine which of the following are correct. Choose one or more:

B.If light has infinite speed, an eclipse would be seen to happen at the same time regardless of how far away Earth is from Jupiter. C.If light has finite speed, it would take longer for it to travel from Jupiter to Earth when Earth is farther from Jupiter.

Label each region of the Sun with the most important process that is happening there.

Core to edge: 1. Nuclear fusion reactions create energy 2. (Radiative zone) Energy is absorbed, emitted, and deflected by matter in unpredictable directions. 3. Moving matter physically transports energy outward 4. (Convective Zone) Energy radiates outward at the speed of light.

Which of the following are reasons that gravity is important to star and planet formation? Choose all that apply.

B.Once bodies are large enough, gravity pulls them together to make even larger bodies. C.Gravity causes the cloud to collapse.

Neutrinos pass straight through solid matter, making them difficult to detect. Luckily, they do react with one type of force—the nuclear weak force. For instance, on extremely rare occasions, a neutrino may interact via the nuclear weak force with a chlorine atom, turning it into a radioactive argon isotope. However, this is rare enough that we would almost never witness this type of reaction in the natural world. Which of these actions would improve our chances of seeing this reaction and thus detecting the presence of a solar neutrino?

Build a detector made of a large amount of chlorine. Go to a place where there are a lot of solar neutrinos.

The light bulb used in class was used to demonstrate both the black body effects as it got hotter and produced what kind of spectrum?

Continuum

The mass of hydrogen is 1.6726 x 10-27 kg, and the mass of helium is 6.6465 x 10-27 kg. Given this, which of the following nuclear reactions would result in a decrease of total mass, and thus a release of energy, while keeping the same number of particles involved?

Four hydrogen nuclei combine into one helium nucleus.

We never quantified light gathering power (LGP) for a telescope, but we did say that the aperture size, which is essentially the size of the primary objective, is the important factor because we want to increase the area of the light collecting surface. Since the area of a circular objective is proportional to the square of the diameter of the objective (or aperture) we can simply take a ratio of the squares of two telescope's diameters to compare how much more light one collects vs another. Given these facts how much more light will an 8 inch telescope collect vs a 4 inch telescope?

Four times as much.

Study the sizes of the gas giants shown in the image above (the distance from the Sun increases from left to right), and choose the best explanation that accounts for their differences in size.

Gas giants decrease in size with increased distance from the Sun because the Solar Nebula was less dense farther out.

Why is the Hubble Space Telescope (HST) resolution better than a similar telescope of the same size that is observing from earth?

HST is truly diffraction limited resolving power while the earthbound scope is dominated by atmospheric seeing.

The gas tube demonstrated in class was of what element?

Hydrogen

Study this picture of a meteorite that has been sliced open to show its interior, and use your observations to determine the most likely formation scenario for a planet.

Individual particles in the nebula stick together to form larger pieces which later collide with and stick to other pieces to gradually form larger objects, which eventually grow to the size of a planet.

Why is the Hubble Space Telescope in space instead of on the ground?

It avoids atmospheric distortion. It observes in the UV.

What is significant about the planet Kepler 16b?

It orbits a binary star system.

If the integration time is long enough to collect the light from this entire animation, what effect would seeing have on the image of the object?

It would blur the light from the object, effectively increasing the angular resolution of the telescope.

Correctly position these four planets within the accretion disk of our early Solar System based on the materials that were present where they formed.

Left to right: 1. Earth 2. Jupiter 3. Saturn 4. Uranus

Examine the telescope depicted here. What is the objective of this telescope, where is it, and by what process does the objective focus the light?

Lens; in the front of the tube; refraction.

The vast distances between astronomical objects and us make them particularly difficult to study. Improvements in technology over the last few hundred years have increased our understanding of the universe, and in turn the drive to learn more has propelled forward advancements in technology. The biggest technological breakthrough in astronomical observations came with the invention of the telescope, and with Galileo's idea of pointing one at the night sky. What is it about a telescope that makes it better at detecting astronomical sources than the human eye? Both your eye and Galileo's telescope have lenses that bend (refract) light, directing it into focus on the focal plane (your retina, in the case of your eye). Light from each distant point source hits every part of a lens with initially parallel light rays, as shown in the figure below. All the light from that source that hits the lens is then focused to a single point on the detector, making it appear much brighter.Imagine decreasing the size of the lens in the figure above. Which choice below best describes what would happen?

Less total light from the source will hit the lens, making it appear fainter on the detector.

How are modern telescopes designed to have an aperture greater than 40 inches in diameter? Select all choices that are valid.

Make an objective mirror of the size needed, Make an objective out of many smaller mirrors that adds up to an effective primary of the size needed.

The resolution of radio telescopes suffers greatly from the large wavelengths of the light they are observing. What can be done to a radio telescope to improve its angular resolution?

Make its dish bigger.

Which of the following would be the best way to find experimental evidence of the different types of materials that condensed as a function of distance from the Sun during the period of accretion in the Solar Nebula?

Measure the composition of meteorites that originated from different locations within the Solar System.

According to the Exoplanet Encyclopedia (http://exoplanet.eu/) , (Links to an external site.) (Links to an external site.)which includes planets detected by all methods possible to date, how many exoplanets have been detected?

Over 4,600

Why do photons take so much longer than neutrinos to emerge from the Sun?

Photons interact strongly with matter, while neutrinos do not.

The problem of atmospheric seeing motivated the development of adaptive optics. This technology can correct for the change in the path of light in real time, with mirrors that deform to redirect the light rays back into a straight path to the detector. This produces images with much higher resolution, as in the figure below. The original view of the object is on the left; the version improved with adaptive optics is on the right.Besides adding adaptive optics to a telescope, what else can be done to reduce the effects of seeing?

Put the telescope at a higher altitude (the height above sea level).

How do the wavelength and frequency of red light compare to the wavelength and frequency of blue light?

Red light has a longer wavelength and lower frequency than does blue light.

Astronomers have determined that the gas giants are made mostly of hydrogen and helium. Given what you have learned about planetesimal formation through accretion, and the types of materials that condensed at certain distances from the Sun, which of the following is the most likely way that the gas giants formed?

Rock, metal, and ices made of materials such as water, ammonia, and methane, condensed into a solid and grew large enough to gravitationally attract hydrogen and helium gas from the Solar Nebula.

The speed of light was first determined by which scientist?

Rømer

Examine the telescope depicted here. What kind of a telescope is this and how does it manipulate light?

Schmidt-Cassegrain hybrid (refractor + reflector)

What do the images tell you about the relationship between sunspots and solar flares?

Solar flares happen where there are sunspots.

Identify the statement that best describes how the latitude of sunspots varies over a sunspot cycle, which is defined to begin at solar minimum.

Sunspots are at higher latitudes at the beginning of a cycle, and lower latitudes at the end of the cycle.

How can one typically adjust the magnification of any telescope?

Swap out the eyepiece for one of a different focal length.

Consider two telescopes: Tele A with a 2000 mm focal length objective and Tele B with a 1000 mm focal length objective. I only have a single 10 mm focal length eyepiece to use with either one. Which one will produce a greater magnification and by how much?

Tele A will magnify twice as much as Tele B

Which of the two bright stars imaged here is the hotter of the two?

The blue star.

Based on the law of conservation of angular momentum, what would happen to a collapsing cloud of gas and dust--isolated in space with no external forces--as its size decreases?

The cloud will spin faster.

The nebular theory states that star systems form by the gravitational collapse of a cloud of gas and dust that, to match observations, must flatten into a disk within which planets can form. Why would this flattening occur? Consider the law of conservation of angular momentum, which states that a quantity related to the size of an object (its moment of inertia) times the speed of rotation (angular speed) has to remain the same at all times as long as no outside forces act on that object.Based on this law, if a collapsing cloud is isolated in space with no external forces, what must happen to it as its size decreases?

The cloud will spin faster.

The solar corona has a temperature of more than a million kelvins; the photosphere has a temperature of only about 6000 K. Why isn't the corona significantly brighter than the photosphere?

The corona has a much lower density.

The largest astronomical refractor has an aperture of 1 meter. Select all true statements below about why it would be impractical to build an even larger refractor with, say, twice the aperture.

The degree of chromatic aberration increases as the focal length gets longer, and this would reduce image quality. A lens with a 2 m diameter would be very heavy and would deform under its own weight within a few years. The tube would have to be so long that housing and moving it would be extremely difficult, especially because it would be frontloaded with weight.

If the wavelength of a beam of light were to double, how would that affect its frequency?

The frequency would be two times smaller.

If you had a telescope with the same-sized lens (and same focal length) as the human eye, what would be the benefit of taking an exposure of a steady light source with an integration time of 10 seconds?

The light source would appear brighter in the image.

How do protons ever fuse together in the presence of the electromagnetic force? There is another force involved here called the nuclear strong force. It is the strongest of all the forces, but it only acts over extremely small distances before it becomes too weak to matter. If protons and neutrons are able to get close enough to one another, the strong force provides a powerful attractive force that can bind them together in a nucleus, despite the electromagnetic force. Watch the AstroTour on The Solar Core. Then choose the condition that would make it more likely for two nuclei to fuse together.

The nuclei are moving fast with respect to one another.

The video described one of the problems for habitability of earth-like planets that orbit red dwarf stars. What is this problem?

The planet would have to be so close that it may be tidally locked and have a side that is too hot and another side that is too cold.

If there were two telescopes with the same diameter, but one is a visible light telescope and the other a radio telescope, how would the resolution of the images from each telescope compare? The wavelength of visible light is several hundred nanometers (1 nanometer = 10-9 meters), and radio can be several centimeters (1 cm = 10-2 meters) or several meters.

The radio telescope would have much worse angular resolution.

Space telescopes that exist in orbit above most of Earth's atmosphere are expensive, so they must therefore be supported with a very compelling motivation. If you were trying to justify funding for a space telescope in orbit around the Earth, which of the following would be the best argument to use?

The telescope could observe wavelengths of light that are not visible from the ground.

The first neutrino detector (Homestake, shown in this image) consisted of a 100,000 gallon tank of a chlorine-containing liquid, built 1,500 meters underground to block out particles other than neutrinos that might affect the results. Calculations from the model of the nuclear reactions expected to occur in the Sun predicted that it would detect about 1 neutrino every day as it turned a chlorine atom into argon. In actuality, only 1 neutrino was detected about every 3 days. This was referred to as the solar neutrino problem. What might this problem imply?

There were fewer neutrinos detected than expected, so something might be wrong with our models. The detector may have been missing some neutrinos for some reason.

This figure explains how molecular clouds naturally fragment, resulting in star clusters such as the Pleiades. The Sun also likely formed in a cluster, from a single molecular cloud that fragmented to form hundreds or thousands of stars at once with a full range of masses. Yet the Sun (and most other stars) is currently a single star, with no sign of the siblings it formed with. What likely happened to the other stars in the cluster the Sun was born in?

They moved away from the Sun over the past 4.5 billion years.

There is a particle produced in the Sun's nuclear reactions that we can use to directly study what is happening in the interior. Neutrinos are weakly interacting particles, and they have almost no mass and no charge. They are not affected at all by the nuclear strong force. As neutrinos travel through the Sun's dense interior, how will their path change due to the presence of the gravitational, electromagnetic, and nuclear strong forces around them?

They will not change at all.

Drag each type of material to the bar indicating where each could be found in the forming Solar System.

Top to bottom: 1. Refractory materials 2. Water ice 3. Highly volatile materials

Which method of extrasolar planet discovery requires the planet to periodically pass in front of the host star?

Transit

Which method of extrasolar planet discovery is the only one that provides us with information on the planet's size?

Transits

A region around a star where a planet can have liquid water is considered a habitable region and is often referred to as the Goldilocks Zone.

True

Every element has its own unique pattern of spectra, which allows us to identify substances by analyzing their light.

True

It was said in the video that some planets may be water worlds and some were so close to their host stars that they would have molten surfaces.

True

Only a few exoplanets have been detected by direct visual (or infrared) observations, Fomalhaut b is one example. https://earthsky.org/brightest-stars/solitary-fomalhaut-guards-the-southern-sky

True

The Sun is a source of white light.

True

It was discovered that there are three different types of neutrinos, called flavors, and that neutrinos can spontaneously change from one type to another. Electron neutrinos are produced in the Sun's core, but they can change into a muon or tau neutrino during their trip to Earth. The first detectors were built only to detect electron neutrinos. Can this new information solve the neutrino problem and confirm that our models of nuclear reactions in the Sun are correct?

Yes. The existence of three different types of neutrinos would account for the missing neutrinos observed over the number that were predicted.

Study the Earth view panel at the top of the window. Would this planet be a good candidate for a transit observation? Why or why not?

Yes. The planet passes in front of the star from the Earth's point of view.

Watch the first section, and click through, using the "Play" button until you reach Section 2 of 3.Here we will explore the following questions: How many properties does a wave have? Are any of these related to each other?Work your way through to the experimental section, where you can adjust the properties of the wave. Watch the simulation for a moment to see how fast the frequency counter increases.Reset the simulation, and increase the frequency. Did the wavelength change in the expected way based on the relationship between wavelength and frequency?

Yes. The wavelength decreased as expected.

A light wave does not require:

a medium.

Larger lenses in telescopes offer better resolution. Resolution is defined as the closest angular distance two objects can be apart from one another before their light merges together and they look like just one object. Therefore, smaller resolutions are better (closer objects can be separated). The resolution of the human eye is 1 arcminute, or 1/60th of a degree. If the light of two street lamps in the distance is separated by 0.5 arcminute, what will you see with your eyes?

a single light, with the combined brightness of each street lamp

At the point in time the video was made, they claim that most sizes of exoplanets thus far found were...

a variety sizes ranging from 1/2 earth size to several times Jupiter's size.

The following image and accompanying plot of the Solar spectrum is an example of:

an absorption spectrum.

When hydrogen is fused into helium, energy is released from

conversion of mass to energy.

The tool we used in class to analyze several light sources worked by the principle of:

diffraction

The equation described in class allows for the magnification of a telescope to be found by...

dividing the primary objective's focal length by the eyepiece's focal length.

In the Sun, four hydrogen nuclei do not fuse directly into a helium nucleus. The overall reaction involves several steps, and other particles are also produced in the process.Study the AstroTour about The Solar Core. Then select all the particles/elements that are created by the reaction.

helium, neutrino, positron, gamma ray

The Doppler-shift method for detecting the presence of exoplanets is best able to detect:

massive planets near the star.

Notice that when the planet moves away from the Earth, the star moves toward Earth. The sign of the radial velocity tells the direction of the motion (toward or away).At this phase in the orbit, the radial velocity of the star is __________, and the planet's radial velocity is __________ .

negative; positive

Hydrostatic equilibrium in the Sun means that

pressure balances the weight of overlying layers

Which of the following lists different types of electromagnetic radiation in order of decreasing wavelength (from longest to shortest)?

radio waves, infrared, visible, ultraviolet, X-rays, gamma rays

A prism is able to spread white light into a spectrum of colors based on the process of:

refraction.

The transit method for detecting exoplanets works best for...

solar systems seen edge on.

The direction of revolution in the plane of the Solar System was determined by

the direction of rotation of the original cloud.

Sunspots change in number and location during the solar cycle. This phenomenon is connected to

the magnetic field of the Sun.

The advantage of an interferometer is that

the resolution is dramatically increased.

Based on the above graph, which of these types of light from astronomical sources are not observable from the ground?

ultraviolet at 100 nm infrared at 100 micrometer (10-4 m) gamma ray X-ray

Which of the following can be observed from Earth's surface?

visible light radio waves