Discovering Astronomy

Using the light curve of a star with a transiting exoplanet graph, what is the period in years of the transiting exoplanet?

1

Sunspots peak every _____ years, a consequence of the ____-year magnetic solar cycle.

11, 22

Suppose that astronomers discover a new planet in the outer solar system, very far from Earth, at an average orbital distance of 554 AU. How many times longer does it take this newly discovered planet to orbit the Sun than Earth?

13,039.6

Most of the stars in the Milky Way cannot be seen from Earth because of:

interstellar gas and dust.

Energy is released from atoms in the form of light when electrons

move from high energy levels to low energy levels.

Hydrogen emits light at 6560 Å. You see a distant galaxy in which the light from hydrogen has 6960 Å. This galaxy is

moving away from us.

Stars we see in the halo of our galaxy (or in globular clusters) formed even before the Milky Way collapsed into a disk. Since we see them now, they must be:

old, low-mass

What observations led astronomers to conclude that universe was currently dominated by an as yet unknown component that they called "dark energy"?

- Distant supernovae appeared fainter than expected, indicating the expansion of the universe was slower at an earlier time. - The power spectrum of variations in the cosmic microwave background were observed to best match a universe with a mix of dark energy, dark matter, and visible matter.

How does solar activity affect Earth?

- It can cause geomagnetic storms. - It can sometimes (very rarely) disrupt electrical power. - It can occasionally harm satellites. - It can make beautiful aurorae.

Which of the following are properties of the young universe revealed by the cosmic microwave background?

- It was hot. - It was dense. - It was uniform on large scales. - It was "clumpy" on small scales.

If you could see both the Sun and the other stars during the day, this is what the sky would look like looking south at noon on May 24, 2021 for an observer in the northern hemisphere. Rank the constellations in the order that they will be located from highest in the sky to farthest below the horizon, 6 hours after the time shown.

- Leo - Cancer - Gemini - Taurus - Aries

How can you tell the surface temperature of a star?

- Spectral type - Color: the hottest stars are bluish-white

Which of the following determines the strength of the gravitational interaction between two objects? (Choose all correct answers.)

- The mass of the largest central object - The distance between the two objects - The mass of the smaller object

What conditions must exist for a solar eclipse to occur? Choose all that apply.

- The moon is in the "new" phase - The moon must be passing through Earth's orbital plane

What is likely to happen if two galaxies collide?

- gravitational pull greatly distorts each galaxy - starbursts, greatly enhanced star formation, may occur

The flatness problem related to:

- the density of the universe. - the shape of the universe.

If you could see both the Sun and the other stars during the day, this is what the sky would look like looking south at noon on May 24, 2021 for an observer in the northern hemisphere. Rank the constellations in the order that they would first appear to rise above the horizon on this day.

1. Aries 2. Taurus 3. Gemini 4. Cancer 5. Leo

The four stars listed below are in different stages of their evolution, and in different locations in the Milky Way. Rank these stars from metal-poor to metal-rich.

1. K-type in halo 2. G-type in disk 3. O-type in disk

The four stars listed below are in different stages of their evolution, and in different locations in the Milky Way. Rank these stars from oldest to youngest.

1. K-type in halo 2. G-type in disk 3. O-type in disk

Stars in elliptical galaxies have velocities that ________, while stars in the disks of spiral galaxies have orbits that ________.

1. are oriented in random directions 2. mostly aligned in the same plane

Recent observations indicate that the Hubble plot for our universe actually looks more like the plot on the right. The Hubble constant as measured now is very close to H = 21 km/s/Mly, but has been observed to change with time! This is based on the measurements of distant white dwarf supernovae with the Hubble Space Telescope and large ground-based infrared telescopes. Three astronomers won the Nobel prize in 2011 for these measurements. 1. The galaxies from which we receive light that was emitted closest to our present time can be found in the ________. 2. The galaxies from which we receive light that was emitted furthest from our present time can be found in the ________. 3. The galaxies that are moving away from us with the fastest velocities are in the ________. 4. The galaxies that are moving away from us with the slowest velocities are in the ________. 5. The portion of the graph that corresponds to the fastest expansion rate is in the ________. 6. The portion of the graph that corresponds to the slowest expansion rate is in the ________.

1. lower left 2. upper right 3. upper right 4. lower left 5. lower left 6. upper right

Assume that our best guess for the length of Eratosthenes "stadium" is about 0.16 km is correct. Then Eratosthenes found a circumference of about 40,000 km for the Earth. What did Eratosthenes find for the radius of the Earth? Give your answer in km.

6369.43

Approximately what percentage of the stars in our galaxy have planets in orbit?

80% or more

Graphs of radial velocity as a function of time are shown for four stars with exoplanets. Assume that the stars are identical and are orbited by identical planets. For which case would you expect the planet to be orbiting closest to the star?

A

About how many stars are there in our galaxy?

A few hundred billion

Imagine you are comparing the five electric hot plates (A - E) of different sizes and temperatures. The temperature of each hot plate is indicated by a shade of gray such that the lighter the shade of gray, the higher the temperature of the hot plate. Which of the following shows the correct ranking of the total energy output or luminosity (from greatest to least) of the hotplates?

A > E > C > B > D

What is a star?

A hot ball of gas that produces energy by combining atoms into heavier atoms

Based on being able to detect its wavelength, and cost-effectiveness of location, which telescope should be funded?

A near-infrared telescope on an aircraft (45,000' altitude).

Why do Jupiter, Saturn, Uranus, and Neptune all have rings?

All have small moons and small orbiting particles that constantly collide and make rings.

Below are drawings of three different exoplanet orbits. The masses of the planets and stars are provided along with the distance between them. Which star has the most redshifted spectrum (i.e. largest velocity)? Recall that the orbital velocity of a planet around a star is proportional to the square root of the star's mass divided by the orbital distance of the planet:

B

Graphs of radial velocity as a function of time are shown for four stars with exoplanets. Assume that the stars are identical and are orbited by identical planets. For which case would you expect the planet to be orbiting farthest from the star?

B

While an observer in Jacksonville, FL, is looking at a full moon, which Earth phase would be seen by an observer on the side of the moon facing Earth?

D

With a very accurate spectrometer you graph the doppler shift of lines in a star's spectrum as they move back and forth revealing the orbit of a single exoplanet around this star. Given the figure below, with the black filled circle marking the current radial velocity of the star's lines, at which of the positions is the planet currently located? Note the arrow indicating the direction toward Earth, from where you are observing this star. Remember, blue is towards you, red is away.

D

In the figures below, parallel beams of sunlight illuminate globes tilted at various angles. Like the Earth, the globes rotate so that each location (indicated by an X) on each globe is sometimes in sunlight and sometimes in darkness. Assume that the globes make one full rotation every 24 hours, and that the distance of each "X" above the equator is the same on each globe. Imagine that you placed identical glasses of water at each location indicated by an "X" for globes A - E. Rank the temperature (from coolest to hottest) a glass of water would reach during a 24 hour period at each location.

D A C B E

Imagine you are comparing the five electric hot plates (A - E) of different sizes and temperatures. The temperature of each hot plate is indicated by a shade of gray such that the lighter the shade of gray, the higher the temperature of the hot plate. Which of the following shows the correct ranking of the temperature (from hottest to coldest) of the hotplates?

E = A > C > D = B

In the figures below, parallel beams of sunlight illuminate globes tilted at various angles. Like the Earth, the globes rotate so that each location (indicated by an X) on each globe is sometimes in sunlight and sometimes in darkness. Assume that the globes make one full rotation every 24 hours, and that the distance of each "X" above the equator is the same on each globe. Rank the time (from longest to shortest) that each location spends in daylight during the 24 hour rotation period.

E B C A D

Match the following views (numbered 1-5) that would be seen from each location [A]-[E] in space in the diagram above. Remember that the diagram above is seen from the side.

E B D A C

During the period each year when we see Mars undergoing apparent retrograde motion in our sky, what is really going on in space?

Earth is catching up with and passing by Mars in their respective orbits.

Which of these is not a reason to think there might be other forms of life in the Solar System?

Enceladus is out of the Sun's habitable zone.

On about September 22, the Sun sets directly to the west as shown on the diagram below. Where would the Sun appear to set two weeks later?

Farther South

The expansion rate of the universe determines how fast the universe increases in size with time. For example, a universe that is tripling in size has a faster expansion rate than a universe that is doubling in size over the same amount of time. Each of the three Hubble plots below depicts a different possible universe. Rank the expansion rate (from fastest to slowest) that each universe would be experiencing.

Fastest: A Middle: B Slowest: C

Consider the small section of the universe containing four galaxies (A-D) shown in the figure below. The distances between each galaxy are also shown. Imagine that this section of the universe doubles in size over time due to the expansion of the universe. Which of the galaxies (B-D) increased its distance from Galaxy A by the greatest number of light-years during this time?

Galaxy B Explanation: Galaxy B by 6b light-years, Galaxy C by 4b light-years, Galaxy D by 5b light-years.

Hubble's law and the Big Bang theory are related because:

Hubble's law is an observation that led to the development of the theory.

Surprising discovery? Saturn's core is pockmarked with impact craters and dotted with volcanoes erupting basaltic lava.

Implausible. No impactors would survive the immense pressures at the depth of Saturn's core.

Surprising discovery? A mission to the outer solar system finds a new dwarf planet that has lakes of liquid water on its surface.

Implausible. Water would be frozen at the equilibrium temperature of a body in the outer solar system, and we know of no extra heat sources.

Hubble's law relates the distance between two galaxies and the speed at which that galaxy appears to be moving away from the other galaxy. We can depict this law as a plot of the speed at which a galaxy appears to move away from us versus its distance from us. This is called a Hubble plot, shown in Figure A. Each dot represents a galaxy observed from Earth. Which of the following plots shows the correct Hubble plot that observers in Galaxy 3 would construct with the locations of all other galaxies, including the Milky Way, labeled?

In order, plots 3, (2 & 4), (1 & 5), MW.

If the Sun were suddenly replaced by a 1 solar mass black hole, how would the Earth's orbital distance change?

It would not change.

How would the apparent brightness of Alpha Centauri change if it were five times farther away?

It would only be 1/25 as bright.

Two planets are observed going around a star. Planet Xoron has an orbital period that is half as long as Planet Krypton. Which planet has a larger average orbital radius?

Krypton

The diagram (not to scale) below shows the side view of the different shadow zones that are created by an obstacle that blocks light from the sun, and five different locations A to E in space to observe from. (This obstacle may either be Earth or the moon.)

Location A - none Location B - the top edge Location C - the bottom edge Location D - the top and bottom edges

What two factors determine how bright a star appears to be in the sky?

Luminosity and distance

Consider the following discussion between two students about the different properties of light. Student 1: I think I get how light works. If you look at the chart of the electromagnetic spectrum, it shows that light with a higher frequency will also have a long wavelength. But it all has the same speed. Student 2: I disagree. If one type of light has a lot of energy and a high frequency, it will have a faster speed than light that has a lower energy and a low frequency. Which student is correct?

Neither student is correct.

As seen from your current location, when will an upright flag pole cast no shadow because the Sun is directly above the flagpole?

Never from your current location.

Which of the following astronomers first proposed the heliocentric model of the solar system?

Nicholas Copernicus

If fusion in the solar core ceased today, would worldwide panic break out tomorrow as the Sun would begin to grow dimmer?

No, it takes thousands of years for photons created in nuclear reactions as the solar core to reach the surface.

Consider the discussion among three students about a galaxy that appears red. Student 1: Because there is mainly red light in this galaxy and no blue light, I think that only small, red stars formed in this galaxy and not any big 'blue ones'. Student 2: I disagree. It's just that blue stars don't last very long. I think the blue stars that may have been there in the past have already evolved into red giants, so the galaxy looks red due to the light from all the red giants. Student 3: Wait a minute. I think you are both wrong. I thought that both blue stars and red giants live short lives, so they should both be gone. I think that all the blue stars that formed earl yon have evolved into the red stars that are there now. So the galaxy appears red because it's full of a lot of old, red stars that used to be blue stars. Which student(s) are correct?

None of the students are correct.

The graphs below illustrate the energy output versus wavelength for three unknown objects A, B, and C. Which of the following statements is correct?

Object B has a hotter temperature than objects A and C

The expansion rate of the universe determines how fast the universe increases in size with time. For example, a universe that is tripling in size has a faster expansion rate than a universe that is doubling in size over the same amount of time. Each of the three Hubble plots below depicts a different possible universe. Now rank the age (from oldest to youngest) of each universe based on the amount of time it would have taken each universe to reach a particular size.

Oldest: C Middle: B Youngest: A

Why don't the planets fall into the Sun? (Choose the best answer.)

Planets are always falling towards the Sun, but also moving sideways so they keep missing it.

Which of the following would make you weigh half as much as you do right now? (Choose all the correct answers.)

Take away half of the Earth's mass

The expansion rate of the universe determines how fast the universe increases in size with time. For example, a universe that is tripling in size has a faster expansion rate than a universe that is doubling in size over the same amount of time. Each of the three Hubble plots below depicts a different possible universe. Rank the average distances (from smallest to largest) between the galaxies in each universe for the particular case in which they all started at the same time and have been in existence for the same amount of time.

Smallest: C Middle: B Largest: A

Recently, folks have started called total lunar eclipses the "blood moon." I think "lunar eclipse" sounds cool enough, but why does the Moon look reddish to us when there is a total lunar eclipse?

The Earth's atmosphere bends different colors of light to a different degree. During a total lunar eclipse, the red light of the Sun, filtering through the Earth's atmosphere colors the moon red.

What causes the blue and red colors to come out in a photograph of a typical nebula, such as shown below?

The blue color is due to the scattering of light by interstellar dust grains and the red color arises from a hydrogen emission line.

How did the planets orbiting the Sun form?

The planets formed from the same materials as the Sun.

Which of the following would be true about comparing visible light and radio waves?

The radio waves would have a longer wavelength and travel the same speed as visible light.

Each of the following planets has the same mass M, but each is made of a different material. The darker the planet, the denser the material. Which statement best describes the strength of gravity that a rocket at a distance R from the center of each planet experiences?

The strength of gravitational force on the rocket is the same for all, because the planets have equal masses and the rocket is at an equal distance.

The plot shows five blackbody curves representing the brightness of a star (vertical axis) as a function of wavelength in nanometers (horizontal axis). Which of the following is the correct ranking of the luminosity of the stars as seen from Earth?

There is not enough information.

Why are smaller terrestrial bodies such as Mercury or the Moon "geologically dead"?

They cooled off faster than Earth did

Why do elliptical galaxies not produce new, young stars?

They do not have enough gas and dust.

The Sun rises in the east and sets in the west. Which way is Earth rotating?

Toward the east

Which sentence best describes why the Moon goes through phases?

We see only part of the lit-up face of the Moon depending on its position relative to Earth and the Sun.

If the ecliptic were aligned with the celestial equator, what would happen to the seasons?

We would not have seasons at all.

How would you compare the strength of gravity at the surface of Pluto with the strength of gravity at the surface of the Earth? (Choose the best answer.)

Weaker, because Pluto is smaller and less mass.

Which of the following would most likely give off the most energy?

a blue star 10 times the size (diameter) of the Sun

Einstein suggested that the regular change (advance) in the perihelion of the planet Mercury could be explained by:

a distortion in spacetime caused by the gravity of the Sun

Which of these planets would scientists suspect is most likely to hold life?

a planet near a K-class star

Dark matter in the Milky Way is located:

above and below the disk, in the halo

Astronomers put telescopes in space to:

avoid atmospheric effects.

The image above shows a molecular cloud in which stars are currently forming. There are three "pillars" visible. One is bright and two are dark. From front to back, how are these pillars and the light source arranged?

black pillars, light source, colored pillar

The __________ of Cepheid variable stars in globular clusters allows their distances to be determined.

changing brightnesses

If a universe is dominated by matter, it will:

expand and then contract.

If a universe is dominated by dark energy, it will:

expand forever.

The nuclear fusion rate for a massive star is _________ a low-mass star.

faster than

Using the light curve of a star with a transiting exoplanet graph, when does the exoplanet complete one full transit across its parent star?

from A to C

Molecular clouds collapse because of:

gravity

Radio telescopes are larger in diameter than optical telescopes in order to have a comparable resolving power because radio waves __________ than visible light.

have longer wavelengths

To maintain a stable size, the sun uses _____________ to counteract gravity.

hydrogen fusion

To predict whether a star will ultimately become a black hole, what is the key property of the star we should look at?

mass

Which one property of a star will determine the rest of the characteristics of that star's life?

mass

The fusion rate of a 4.0 solar mass star would be _______ the sun's.

more than four times

The physical models of the Sun's interior have been confirmed by observations of:

neutrinos and seismic vibrations.

The Milky Way's total mass can be determined by observing:

orbital motions of stars.

Fusion requires high temperatures such that nuclei can:

overcome electric repulsion between charged nuclei.

A(n) __________ telescope would benefit the least by being taken up into outer space.

radio wave

Adaptive optics is used in modern optical telescopes to improve:

resolving power.

Consider four different stars W-Z, on the Hertzsprung-Russell diagram. The luminosity and temperature of the sun is indicated for reference, compared to star W-Z. Which star has the coolest temperature?

star Z and star X

Consider four different stars W-Z, on the Hertzsprung-Russell diagram. The luminosity and temperature of the sun is indicated for reference, compared to star W-Z. Which star has the reddest color?

star Z and star X

Which of Galileo's discoveries provided the greatest evidence that the Sun must be at the center of the solar system?

that Venus goes through phases

The CMB and the Big Bang theory are related because:

the Big Bang theory predicted the existence of the CMB.

The horizon problem states that:

the cosmic microwave background is too uniform.

The flatness problem states that:

the cosmological constant is too close to 1.

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

the direction of rotation of the original molecular cloud.

Which of the following statements are true? In general, the expansion of the universe causes: A) the distances between stars in the galaxy to increase. B) the distances between galaxies in the universe to increase. C) the distances between planets in the solar system to increase. D) None of the above.

the distances between galaxies in the universe to increase.

The terrestrial planets and the giant planets have different compositions because:

the giant planets are much farther from the Sun.

The terrestrial planets are different from the giant planets because when they formed:

the inner solar system was hotter than the outer solar system.

The cosmic microwave background looks like the spectrum of a blackbody at the low temperature of 2.73 K because:

the light has been redshifted since it was last scattered.

Which of the following is evidence that the formation process of our Galaxy may have included collisions with smaller neighbor galaxies?

the observation of long moving streams of stars that continue to orbit through our Galaxy's halo

According to Einstein's general theory of relativity, the stronger a star's gravity:

the slower time runs near it.

Even if there's a very low chance that any one planet has life on it, there may be many advanced civilizations because:

there are billions of billions of stars in the universe.

Sunspots appear dark because:

they are cooler than their surroundings.