ASTR HW 5, Chapter 3 Quiz AST2002, Process of Science: Observation Techniques, Mastering Astronomy, Astronomy 2, Chapter 6, Astro ch6, ASTR 102 Chapter 6: Telescopes: Portals of Discovery, Astronomy 101 Study Guide

Which of the following forms of light can be observed with telescopes at sea level? Select all that apply. Select all that apply. X rays ultraviolet light visible light infrared light radio waves

visible light radio waves

When we look at an object that is 1,000 light-years away we see it _

as it was 1,000 years ago

When we look at an object that is 1,000 light-years away we see it _________.

as it was 1,000 years ago

Consider an atom of carbon in which the nucleus contains 6 protons and 7 neutrons. What is its atomic number and atomic mass number?

atomic number = 6; atomic mass number = 13

Gamma rays have a very small ______.

wavelength

Suppose we look at two distant galaxies: Galaxy 1 is twice as far away as Galaxy 2. In that case

we are seeing Galaxy 1 as it looked at an earlier time in the history of the universe than Galaxy 2

Suppose we look at two distant galaxies: Galaxy 1 is twice as far away as Galaxy 2. In that case _________.

we are seeing Galaxy 1 as it looked at an earlier time in the history of the universe than Galaxy 2

The star Betelgeuse is about 600 light-years away. If it explodes tonight,

we won't know about it until 600 years from now.

If we imagine the history of the universe compressed into one year, dinosaurs became extinct

yesterday morning

If we imagine the history of the universe compressed into one year, dinosaurs became extinct _________.

yesterday morning

planet

A moderately large object that orbits a star and shines primarily by reflecting light from its star. According to the current definition, an object can be considered a planet only if it orbits a star, is large enough for its own gravity to make it round, and has cleared most other objects from its orbital path.

Which of the following statements about electrons is not true?

Electrons orbit the nucleus rather like planets orbiting the Sun.

In which case will the woman see a rainbow of color interrupted by a few dark absorption lines?

Hot light source and thin cloud of cool gas The hot light source produces a continuous spectrum, but the cool gas absorbs light at specific wavelengths, so that she sees an absorption line spectrum.

It doesn't --- Earth's orbital distance plays no significant role in the seasons.

How does Earth's varying distance from the Sun affect our seasons?

Which of the following statements is true of green grass? It absorbs red light and emits green light. It means the lawn is healthy. It absorbs red light and reflects green light. It transmits all colors of light except green.

It absorbs red light and reflects green light.

What is the purpose of interferometry?

It allows two or more small telescopes to achieve the angular resolution of a much larger telescope

If you see the color red in an X-ray image from the Chandra X-Ray Observatory, it means ...

It depends: the colors are chosen arbitrarily to represent something about the X rays recorded by the telescope

The twinkling of stars is caused by ...

Motion of air in our atmosphere.

If you wanted a radio telescope to achieve the same angular resolution as a visible-light telescope, it would need to be ...

Much larger

dark energy

Name sometimes given to energy that could be causing the expansion of the universe to accelerate. see cosmological constant.

Using the ideas discussed in your textbook, in what sense are we "star stuff"?

Nearly every atom from which we are made was once inside of a star.

Could we see a galaxy that is 20 billion light-years away? (Assume that we mean a "lookback time" of 20 billion years.)

No, because it would be beyond the bounds of our observable universe.

Could we see a galaxy that is 50 billion light-years away?

No, because it would be beyond the bounds of our observable universe.

Figure showing a laboratory spectrum on the top and four object spectra underneath. Now consider Object 2. What can you say about Object 2 in comparison to Object 1? Object 1 had a higher temperature than Object 2. Object 2 contains more hydrogen than Object 1. Object 2 is moving away from us faster than Object 1. Object 2 is moving toward us while Object 1 is moving away from us.

Object 2 is moving away from us faster than Object 1. Object 2's lines are shifted farther to the right than Object 1's, which means it has a greater redshift and is moving away faster.

dark matter

Matter that we infer to exist from its gravitational effects but from which we have not detected any light; dark matter apparently dominates the total mass of the universe.

Put the following into perspective: the size of our solar system; the distance to nearby stars; the size of the Milky Way Galaxy; the size of the observable universe. Rank from largest to smallest. To rank items as equivalent, overlap them.

The observable universe, The Milky Way Galaxy, Distances to nearby stars, solar system

orbit (or revolution)

The orbital motion of one object around another due to gravity. For example, Earth orbits the Sun once each year.

revolution

The orbital motion of one object around another.

Which of the following best describes why we say that light is an electromagnetic wave?

The passage of a light wave can cause electrically charged particles to move up and down.

All of the following statements about the Sun's corona are true. Which one explains why it is a source of X rays?

The temperature of the corona's gas is some 1 to 2 million Kelvin.

Which of the following is not a reason why telescopes tend to be built on mountaintops that are relatively far from cities and are in regions with dry climates?

The thin air on mountaintops makes the glass in telescope mirrors less susceptible to warping.

Studying a spectrum from a star can tell us a lot. All of the following statements are true except one. Which statement is not true?

The total amount of light in the spectrum tells us the star's radius.

If you heat a gas so that collisions are continually bumping electrons to higher energy levels, when the electrons fall back to lower energy levels the gas produces an emission line spectrum. radio waves. thermal radiation. X-rays. an absorption line spectrum.

an emission line spectrum.

The ___________ of the Hubble Space Telescope is better for shorter (bluer) wavelengths of light than for longer (redder) wavelengths of light

angular resolution

Assume the woman in the figure uses her prism to look at a spectrum of light coming from the object(s) shown. In which case will she see a continuous rainbow of thermal radiation?

prism to hot light source A hot light source produces a continuous spectrum (of thermal radiation)

Thermal radiation is defined as _________.

radiation with a spectrum whose shape depends only on the temperature of the emitting object

The ______ is the layer of the Sun between its core and convection zone

radiation zone

The Very Large Array. What kinds of light are these telescopes designed to detect? radio waves X rays ultraviolet light infrared and visible light light with extremely short wavelengths

radio waves This is the Very Large Array in New Mexico; the many radio telescopes are used together for interferometry.

Which of the following wavelength regions can be studied with telescopes on the ground?

radio, visible, and very limited portions of the infrared and ultraviolet regions

The large research observations on Mauna Kea use giant __________.

reflecting telescopes

Without telescopes or other aid, we can look up and see the Moon in the night sky because it glows through radioactive decay. reflects visible light. emits thermal radiation. emits visible light. reflects infrared light.

reflects visible light.

Galileo's telescope designs using lenses were examples of ____________.

refracting telescopes

When your eye forms an image, the _____ plays a role analogous to the detector in a camera.

retina

galaxy cluster

see cluster of galaxies.

star system

see solar system.

On a scale in which the distance from Earth to the Sun is about 15 meters, the distance from Earth to the Moon is _________.

small enough to fit within your hand

What is the "Raisin Cake model" intended to explain?

that every raisin in a raisin cake moves farther away from every other raisin: there is no special central raisin (and no special central galaxy)

The term observable universe refers to

that portion of the universe that we can see in principle, given the current age of the universe

The term observable universe refers to _________.

that portion of the universe that we can see in principle, given the current age of the universe

Our solar system consists of _________.

the Sun and all the objects that orbit it

An astronomical unit (AU) is _________.

the average distance between Earth and the Sun

big bang

The name given to the event thought to mark the birth of the universe.

universe (or cosmos)

The sum total of all matter and energy—that is, all galaxies and everything between them.

axis tilt

(of a planet in our solar system) The amount by which a planet's axis is tilted with respect to a line perpendicular to the ecliptic plane.

expansion

(of the universe) The idea that the space between galaxies or clusters of galaxies is growing with time.

solar system

(or star system) A star (sometimes more than one star) and all the objects that orbit it.

Suppose you want to determine the chemical composition of a distant planet or star. Which of the following will be most useful to have?

High spectral resolution.

Suppose that Star X and Star Y both have redshifts, but Star X has a larger redshift than Star Y. What can you conclude?

Star X is moving away from us faster than Star Y.

local group

The group of about 40 galaxies to which the Milky Way Galaxy belongs.

expansion (of the universe)

The increase in the average distance between galaxies as time progresses.

If the 14 billion year history of the universe were compressed to one year, and "now" is exactly midnight December 31, approximately how long ago were your grandparents born?

0.15 second ago

Suppose a photon has a frequency of 300 million hertz (300 megahertz). What is its wavelength?

1 meter

1. The ______ of the Hubble Space Telescope is better for shorter (bluer) wavelengths of light than for longer (redder) wavelengths of light. 2.The large research observatories on Mauna Kea use giant ______ 3._____ separate the various colors of light, allowing astronomers to determine stellar composition and many other stellar properties 4.__________ separate the various colors of light, allowing astronomers to determine stellar composition and many other stellar properties 5. The Chandra X-ray observatory focuses X rays with ____ mirrors. 6. A 10-meter telescope has a larger ______ 7.Galileo's telescope designs using lenses were examples of ____

1. Angular Resolution 2. Reflecting Telescopes 3. Spectrographs 4. Interferometry 5. Grazing Incidence 6. Light-collecting area 7. Refracting Telescopes

star

A large, glowing ball of gas that generates energy through nuclear fusion in its core. The term star is sometimes applied to objects that are in the process of becoming true stars (e.g., protostars) and to the remains of stars that have died (e.g., neutron stars).

star

A large, glowing ball of gas that generates heat and light through nuclear fusion in its core. Our Sun is a star.

The value of radio and infrared astronomy is partly based on the fact that light at these wavelengths can travel through cosmic clouds of gas and dust without being absorbed. That means astronomers can observe phenomena in our Galaxy and in other galaxies that otherwise would be hidden from view at optical and shorter wavelengths. Radio emission at centimeter-to-meter wavelengths can be effectively observed from the ground. What are other unique characteristics of radio astronomy within this wavelength range?

1. Areas 2. Baselines 3. Interferometers 4. Storms

Based on observations of the universal expansion, the age of the universe is about _________.

14 billion years

An atom which has 4 protons and 6 neutrons will be electrically neutral if it contains ______.

4 electrons

According to modern science, approximately how old is the Sun? 11,000 years 400 million years 4.5 billion years 25 million years

4.5 billion years

Suppose you have a 100-watt light bulb that you leave turned on for one minute. How much energy does it use?

6,000 joules

cluster of galaxies

A collection of a few dozen or more galaxies bound together by gravity; smaller collections of galaxies are simply called groups.

cluster of galaxies (or group of galaxies)

A collection of galaxies bound together by gravity. Small collections (up to a few dozen galaxies) are generally called groups, while larger collections are called clusters.

The value of X-ray and gamma-ray astronomy is based on the fact that some of the most energetic sources in the cosmos radiate at these wavelengths. Magnetic storms in stellar atmospheres (including storms on the Sun), exploding stars and their nebular remnants, the regions surrounding neutron stars and black holes, and the innermost regions associated with active galactic nuclei characterize the highest energy, shortest wavelength regime. What would you need to obtain a successful X-ray image of a high-energy source?

A cosmic source of high temperature A telescope designed and built to be launched into space

group (of galaxies)

A few to a few dozen galaxies bound together by gravity. see also cluster of galaxies.

supercluster

A gigantic region of space in which many groups and clusters of galaxies are packed more closely together than elsewhere in the universe.

galaxy

A great island of stars in space, all held together by gravity and orbiting a common center, with a total mass equivalent to millions, billions, or even trillions of stars.

galaxy

A great island of stars in space, containing millions, billions, or even trillions of stars, all held together by gravity and orbiting a common center.

Which of the following statements about thermal radiation is always true?

A hot object emits more radiation per unit surface area than a cool object.

Which of the following statements about thermal radiation is always true? A hot object produces more total infrared emission than a cooler object. All the light emitted by hot object has higher energy than the light emitted by a cooler object. A hot object emits more radiation per unit surface area than a cool object. A cold object produces more total infrared and radio emission per unit surface area than a hot object.

A hot object emits more radiation per unit surface area than a cool object. This is part of the first law of thermal radiation (the Stefan-Boltzmann law)

In what wavelength range was interferometry first routinely used? A) radio B) infrared C) optical D) ultraviolet E) X-ray

A) radio

planet

A moderately large object that orbits a star and shines primarily by reflecting light from its star. More precisely, according to a definition approved in 2006, a planet is an object that (1) orbits a star (but is itself neither a star nor a moon); (2) is massive enough for its own gravity to give it a nearly round shape; and (3) has cleared the neighborhood around its orbit. Objects that meet the first two criteria but not the third, including Ceres, Pluto, and Eris, are designated dwarf planets.

In order for an atom to absorb a photon (a particle of light), the photon must have energy matching the difference in energy between energy levels in the atom. the atom must have lost all of its electrons. the photon must have enough energy to remove an electron from the atom. A or C B or C

A or C the photon must have energy matching the difference in energy between energy levels in the atom. the photon must have enough energy to remove an electron from the atom.

Which of the following statements best describes the difference between a refracting telescope and a reflecting telescope?

A refracting telescope uses a transparent glass lens to focus light while a reflecting telescope uses a mirror to focus light

comet

A relatively small and ice-rich object that orbits a star.

asteroid

A relatively small and rocky object that orbits a star.

asteroid

A relatively small and rocky object that orbits a star; asteroids are officially considered part of a category known as "small solar system bodies."

comet

A relatively small, icy object that orbits a star. Like asteroids, comets are officially considered part of a category known as "small solar system bodies."

star system

A star (sometimes more than one star) and any planets and other materials that orbit it.

The diffraction limit is a limit on ...

A telescope's angular resolution.

Which of the following statements best describes the difference between a refracting telescope and a reflecting telescope? A) A refracting telescope uses a transparent glass lens to focus light while a reflecting telescope uses a mirror to focus light. B) A refracting telescope produces refracted images while a reflecting telescope produces reflected images. C) Reflecting telescopes make much clearer images than can refracting telescopes of the same size. D) It is much easier to make a large refracting telescope than a large reflecting telescope.

A) A refracting telescope uses a transparent glass lens to focus light while a reflecting telescope uses a mirror to focus light.

Which of the following best describes why radio telescopes are generally much larger in size than telescopes designed to collect visible light? A) Getting an image of the same angular resolution requires a much larger telescope for radio waves than for visible light. B) Radio telescopes are designed to collect sound rather than light. C) It is because radio telescopes are used in the daytime and visible light telescopes are used at night. D) Objects that emit radio waves are always much larger than objects that emit visible light, and therefore require larger telescopes.

A) Getting an image of the same angular resolution requires a much larger telescope for radio waves than for visible light.

What is the purpose of interferometry? A) It allows two or more small telescopes to achieve the angular resolution of a much larger telescope. B) It allows two or more small telescopes to achieve a larger light-collecting area than they would have independently . C) t is designed to prevent light pollution from interfering with astronomical observations. D) It reduces the twinkling of stars caused by atmospheric turbulence.

A) It allows two or more small telescopes to achieve the angular resolution of a much larger telescope.

What is a CCD? A) It is an electronic detector that can be used in place of photographic film for making images. B) It is an abbreviation for the world's largest operating telescope. C) It refers to any kind of instrument that can be hooked up to a telescope. D) It is a unit used by astronomers to measure angular resolution.

A) It is an electronic detector that can be used in place of photographic film for making images.

Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes? A) It is closer to the stars. B) Stars do not twinkle when observed from space. C) It can observe infrared and ultraviolet light, as well as visible light. D) It never has to close because of bad weather. E) Observers on the ground can use it at any time of day (i.e., not only during their night).

A) It is closer to the stars.

Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes? A) It is closer to the stars. B) Stars do not twinkle when observed from space. C) It can observe infrared and ultraviolet light, as well as visible light. D) It never has to close because of cloudy skies.

A) It is closer to the stars.

What is the purpose of adaptive optics? A) It reduces blurring caused by atmospheric turbulence for telescopes on the ground. B) It allows several small telescopes to work together like a single larger telescope. C) It is a special technology that allows the Hubble Space Telescope to adapt to study many different types of astronomical objects. D) It allows ground-based telescopes to observe ultraviolet light that normally does not penetrate the atmosphere.

A) It reduces blurring caused by atmospheric turbulence for telescopes on the ground.

Consider two future observatories in space. Observatory X consists of a single 50-meter telescope. Observatory Y is an interferometer consisting of five 10-meter telescopes, spread out over a region 100 meters across. Which observatory can detect dimmer stars, and which one can see more detail in its images? (Assume all else is equal, such as quality of optics, types of instruments, and so on.) A) Observatory X can detect dimmer stars and Observatory Y reveals more detail in images. B) Observatory Y can detect dimmer stars and Observatory X reveals more detail in images. C) Observatory X both detects dimmer stars and reveals more detail in images. D) Observatory Y both detects dimmer stars and reveals more detail in images.

A) Observatory X can detect dimmer stars and Observatory Y reveals more detail in images.

Which of the following statements best describes the two principal advantages of telescopes over eyes? A) Telescopes can collect far more light with far better angular resolution. B) Telescopes can collect far more light with far greater magnification. C) Telescopes have much more magnification and better angular resolution. D) Telescopes collect more light and are unaffected by twinkling. E) Telescopes can see farther without image distortion and can record more accurate colors.

A) Telescopes can collect far more light with far better angular resolution.

Which of the following statements best describes the two principle advantages of telescopes over eyes? A) Telescopes can collect far more light with far better angular resolution. B) Telescopes can collect far more light with far greater magnification. C) Telescopes collect more light and are unaffected by twinkling. D) Telescopes have much more magnification and better angular resolution.

A) Telescopes can collect far more light with far better angular resolution.

Which of the following is not a major reason why astronomers would like an observatory on the far side of the Moon? A) Telescopes on the Moon could see objects in all parts of the sky equally well, whereas telescopes on Earth can see only portions of the sky that depend on their latitude. B) Radio astronomy would be advantageous on the Moon because human radio transmissions are less likely to cause interference, especially on the far side of the Moon. C) It would be possible to put telescopes for ultraviolet and X-ray astronomy on the surface, unlike the case on the surface of the Earth. D) Telescopes on the Moon could observe stars even when it is daytime on the Moon.

A) Telescopes on the Moon could see objects in all parts of the sky equally well, whereas telescopes on Earth can see only portions of the sky that depend on their latitude.

How does the light-collecting area of an 8-meter telescope compare to that of a 2-meter telescope? A) The 8-meter telescope has 16 times the light-collecting area of the 2-meter telescope. B) The 8-meter telescope has 4 times the light-collecting area of the 2-meter telescope. C) The 8-meter telescope has 8 times the light-collecting area of the 2-meter telescope. D) The answer cannot be determined from the information given in the question.

A) The 8-meter telescope has 16 times the light-collecting area of the 2-meter telescope.

Which of the following telescopes would benefit most from adaptive optics? A) The Keck I Telescope on Mauna Kea. B) The Hubble Space Telescope. C) The Arecibo Radio Telescope in Puerto Rico. D) The Chandra X-Ray Observatory.

A) The Keck I Telescope on Mauna Kea.

Suppose you have two small photographs of the Moon. Although both look the same at small size, when you blow them up to poster size one of them still looks sharp while the other one becomes fuzzy (grainy) looking. Which of the following statements is true? A) The one that still looks sharp at large size has better (smaller) angular resolution than the one that looks fuzzy . B) The one that looks fuzzy at large size has better angular resolution (smaller) than the one that looks sharp. C) Both photographs have the same angular resolution, because they were both printed at the same sizes in each case. D) Both photographs have the same angular resolution, because they are both photographs of the same object.

A) The one that still looks sharp at large size has better (smaller) angular resolution than the one that looks fuzzy .

Suppose you point your telescope at a distant object. Which of the following is not an advantage of taking a photograph of the object through the telescope as compared to just looking at the object through the telescope? A) The photograph will have far better angular resolution than you can see with your eye. B) By using a long exposure time, the photograph can allow you to see objects that would be too dim to see with your eye. C) If taken with a camera with a sensitive detector such as a CCD, the photograph can capture a much larger percentage of the incoming photons than can your eye. D) The photograph provides a more reliable record of what is seen through the telescope than can a drawing made by eye.

A) The photograph will have far better angular resolution than you can see with your eye.

Which of the following is not a reason why telescopes tend to be built on mountaintops that are relatively far from cities and are in regions with dry climates? A) The thin air on mountaintops makes the glass in telescope mirrors less susceptible to warping. B) Being on a high mountain top means being relatively high in the atmosphere, which tends to limit turbulence. C) Dry regions mean less rain and clouds, and mountaintops in dry regions may even allow some infrared observations. D) Mountaintops far from cities are generally subject to less light pollution than locations nearer to cities.

A) The thin air on mountaintops makes the glass in telescope mirrors less susceptible to warping.

Which of the following is always true about images captured with X-ray telescopes? A) They are always shown with colors that are not the true colors of the objects that were photographed. B) They always are made with adaptive optics. C) They show us light with extremely long wavelengths compared to the wavelengths of visible light. D) They always have very high angular resolution. E) They are always very pretty.

A) They are always shown with colors that are not the true colors of the objects that were photographed.

What is an artificial star? A) a point of light in Earth's atmosphere created by a laser for the purpose of monitoring atmospheric fluctuations B) a satellite orbiting Earth C) a meteor D) a possible source of dark matter in the universe E) the unseen member of a binary star system

A) a point of light in Earth's atmosphere created by a laser for the purpose of monitoring atmospheric fluctuations

Order the following in order of increasing efficiency of detecting photons of visible light. A) eye, photographic film, CCD B) photographic film, CCD, eye C) CCD, eye, photographic film D) CCD, photographic film, eye E) eye, CCD, photographic film

A) eye, photographic film, CCD

Which of the following is not one of the three main categories of observation generally used by astronomers? A) filtering to look at just a single color from an object B) timing to track how an object's brightness varies with time C) spectroscopy to spread an object's light into a spectrum D) imaging to get a picture of an astronomical objects

A) filtering to look at just a single color from an object

At which wavelength range is there no current or planned space observatory? A) radio B) infrared C) visible D) X-ray E) gamma-ray

A) radio

In what part of the electromagnetic spectrum do the biggest telescopes on Earth operate? A) radio B) infrared C) visible D) ultraviolet E) X-ray

A) radio

Which of the following wavelength regions can be studied with telescopes on the ground? A) radio, visible, and very limited portions of the infrared and ultraviolet regions B) all light with wavelengths longer than ultraviolet wavelengths C) all light with wavelengths shorter than infrared wavelengths D) infrared, visible, and ultraviolet light

A) radio, visible, and very limited portions of the infrared and ultraviolet regions

What does angular resolution measure? A) the angular size of the smallest features that the telescope can see B) the brightness of an image C) the size of an image D) the number of electromagnetic waves captured by an image

A) the angular size of the smallest features that the telescope can see

Which of the following could not be measured by an observation that uses only imaging? A) the rate at which a variable star brightens and dims B) the general shape of an interstellar cloud of gas C) the color of a planet D) the brightness of a star in our sky E) the number of bright stars in a nearby star cluster

A) the rate at which a variable star brightens and dims

The stars in our sky twinkle in brightness and color because of ________. A) turbulence in the Earth's atmosphere B) rapid changes in the brightnesses and colors of stars caused by changes in their spectra C) light pollution D) the bubbling and boiling of gases on the surfaces of stars

A) turbulence in the Earth's atmosphere

Which of the following effects is caused by atmospheric turbulence? A) twinkling of stars B) light pollution C) magnification of images D) diffraction of light

A) twinkling of stars

On a scale where the Sun is about the size of a grapefruit and the Earth is about 15 meters away, how far away are the nearest stars besides the Sun?

About the distance across the United States

The Hubble Space Telescope obtains higher-resolution images than most ground-based telescopes because it is ...

Above Earth's atmosphere.

Which technology can allow a single ground-based telescope to achieve images as sharp as those from the Hubble Space Telescope?

Adaptive optics

Which of the following regions of the elctromagnetic spectrum is useful for studying distant galaxies?

All of the above

Which of the following is not a general difference between a planet and a star?

All planets are made of rock and all stars are made of gas.

The orbital plane of the Moon is tilted slightly (by about 5 degrees) to the ecliptic plane.

All the following statements are true. Which one explains the reason that there is not a solar eclipse at every new moon?

cosmos

An alternative name for the universe.

less than the thickness of a human hair held at arm's length

An angle of 1 arcsecond is _________.

Interferometry uses two or more telescopes to achieve ...

An angular resolution equivalent to that of a much larger telescope.

small solar system body

An asteroid, comet, or other object that orbits a star but is too small to qualify as a planet or dwarf planet.

Which of the following transitions within an atom is not possible?

An electron begins in an excited state and then gains enough energy to jump to the ground state.

Suppose you look at a spectrum of visible light by looking through a prism or diffraction grating. How can you decide whether it is an emission line spectrum or an absorption line spectrum?

An emission line spectrum consists of bright lines on a dark background, while an absorption line spectrum consists of dark lines on a rainbow background.

Which of the following changes would cause the fusion rate in the Sun's core to increase? Check all that apply. An increase in the core temperature An increase in the core radius A decrease in the core temperature A decrease in the core radius

An increase in the core temperature & A decrease in the core radius An increase in the core temperature increases the fusion rate because the fusion rate is very sensitive to temperature. A decrease in the core radius causes the core to heat up and increase in density, which therefore leads to an increased fusion rate.

moon

An object that orbits a planet.

moon (or satellite)

An object that orbits a planet. The term satellite is also used more generally to refer to any object orbiting another object.

satellite

Any object orbiting another object.

Each of the following describes an "Atom 1" and an "Atom 2." In which case are the two atoms different isotopes of the same element?

Atom 1: nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons; Atom 2: nucleus with 7 protons and 7 neutrons, surrounded by 7 electrons

How do the speeds at which we are moving with Earth's rotation and orbit compare to the speeds of more familiar objects?

Earth's rotation carries most people around the axis faster than a commercial jet travels, and Earth's orbit carries us around the Sun faster than the Space Shuttle orbits Earth.

Each of the following describes an "Atom 1" and an "Atom 2." In which case are the two atoms different isotopes of the same element? Atom 1: nucleus with 4 protons and 5 neutrons, surrounded by 4 electrons; Atom 2: nucleus with 5 protons and 5 neutrons, surrounded by 4 electrons Atom 1: nucleus with 8 protons and 8 neutrons, surrounded by 8 electrons; Atom 2: nucleus with 8 protons and 8 neutrons, surrounded by 7 electrons Atom 1 : nucleus with 6 protons and 8 neutrons, surrounded by 6 electrons; Atom 2: nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons Atom 1: nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons; Atom 2: nucleus with 7 protons and 7 neutrons, surrounded by 7 electrons

Atom 1: nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons; Atom 2: nucleus with 7 protons and 7 neutrons, surrounded by 7 electrons They are isotopes both atoms have the same atomic number but different atomic mass numbers.

What do we mean when we say that the universe is expanding?

Average distances between galaxies are increasing with time.

Which of the following best describes the principle advantage of CCDs over photographic film? A) CCDs allow long exposures (e.g., minutes or hours) and film does not. B) CCDs capture a much higher percentage of the incoming photons than film. C) CCDs can record the colors of astronomical objects accurately while film cannot. D) CCDs can be attached to modern telescopes more easily than can photographic film.

B) CCDs capture a much higher percentage of the incoming photons than film.

What does the technique of interferometry allow? A) It allows two or more telescopes to obtain a total light-collecting area much larger than the total light- collecting area of the individual telescopes. B) It allows two or more telescopes to obtain the angular resolution of a single telescope much larger than any of the individual telescopes. C) It allows us to determine the chemical composition of stars. D) It allows astronomers to make astronomical observations without interference from light pollution. E) It allows the same telescope to make images with both radio waves and visible light.

B) It allows two or more telescopes to obtain the angular resolution of a single telescope much larger than any of the individual telescopes.

What is meant by spectral resolution? A) It is a measure of how much energy an object emits in different parts of the electromagnetic spectrum. B) It is a measure of how close two spectral lines can be distinguished. C) It is a measure of how close two point sources can be distinguished. D) It is the same as angular resolution when applied to telescopes operating at different wavelengths.

B) It is a measure of how close two spectral lines can be distinguished.

What do we mean by the diffraction limit of a telescope? A) It describes the farthest distance to which the telescope can see. B) It is the angular resolution the telescope could achieve if nothing besides the size of its light-collecting area affected the quality of its images. C) It is the maximum size to which any telescope can be built. D) It describes the maximum exposure time for images captured with the telescope.

B) It is the angular resolution the telescope could achieve if nothing besides the size of its light-collecting area affected the quality of its images.

Which of the following best describes what we mean by the focal plane of a telescope? A) It is the upper surface of the telescope's primary lens or mirror. B) It is the place where, if we mounted film or an electronic detector, we could get a clear (not blurry) image of an object viewed through the telescope. C) It is the lower surface of the telescope's primary lens or mirror. D) It is the surface of the lens on the eyepiece, through which you would look to see objects in the telescope's field of view.

B) It is the place where, if we mounted film or an electronic detector, we could get a clear (not blurry) image of an object viewed through the telescope.

What do astronomers mean by light pollution? A) Light pollution is a type of air pollution created by lightweight gases such as hydrogen and helium. B) Light pollution is light from human sources that makes it difficult to see the stars at night. C) Light pollution means contamination of light caused by chemicals in the Earth's atmosphere. D) Light pollution is a term used to describe the appearance of the sky in regions that are crowded with stars.

B) Light pollution is light from human sources that makes it difficult to see the stars at night.

Suppose the angular separation of two stars is smaller than the angular resolution of your eyes. How will the stars appear to your eyes? A) You will not be able to see these two stars at all. B) The two stars will look like a single point of light. C) The two stars will appear to be touching, looking rather like a small dumbbell. D) You will see two distinct stars. E) You will see only the larger of the two stars, not the smaller one.

B) The two stars will look like a single point of light.

The Chandra X-Ray Observatory must operate in space because: A) X rays are too dangerous to be allowed on the ground. B) X rays do not penetrate Earth's atmosphere. C) X-ray telescopes require the use of grazing incidence mirrors. D) It was built by NASA.

B) X rays do not penetrate Earth's atmosphere.

Telescopes operating at this wavelength must be cooled to observe faint astronomical objects. A) radio B) extreme infrared C) visible D) X-ray E) gamma-ray

B) extreme infrared

Which of the following studies is best suited to astronomical observations that fall into the category called timing? A) studying how different planets differ in their surface compositions B) studying how a star's brightness varies over a period of 3 years C) measuring the rotation rate of a distant star D) determining the age of the solar system

B) studying how a star's brightness varies over a period of 3 years

Which of the following studies is best suited to a timing experiment? A) studying how different stars differ in their chemical compositions B) studying whether a particular star's brightness is steady or variable C) determining the age of the solar system D) measuring the rotation rate of a distant star E) estimating the time since the Big Bang

B) studying whether a particular star's brightness is steady or variable

Which of the following correctly lists our "cosmic address" from small to large?

Earth, solar system, Milky Way Galaxy, Local Group, Local Supercluster, universe

superclusters

The largest known structures in the universe, consisting of many clusters of galaxies, groups of galaxies, and individual galaxies.

What is the purpose of adaptive optics? A) to improve the angular resolution of telescopes in space B) to eliminate the distorting effects of atmospheric turbulence for telescopes on the ground C) to increase the collecting area of telescopes on the ground D) to increase the magnification of telescopes on the ground E) to allow several small telescopes to work together like a single larger telescope

B) to eliminate the distorting effects of atmospheric turbulence for telescopes on the ground

Why do the patterns of the stars in our sky look the same from year to year?

Because the stars in the constellations are so far away.

Which of the following is a principal advantage of CCDs over photographic film? A) CCDs allow long exposures (e.g., minutes or hours), and film does not. B) CCDs can record the colors of astronomical objects accurately, while film cannot. C) CCDs capture a much higher percentage of the incoming photons than does film. D) Images recorded with CCDs never require any image processing, while images recorded by film often do. E) CCDs can be attached to modern telescopes more easily than cameras.

C) CCDs capture a much higher percentage of the incoming photons than does film.

What do astronomers mean by light pollution? A) Light pollution refers to pollution caused by light industry as opposed to heavy industry. B) Light pollution refers to harmful gases emitted by common street lights. C) Light pollution refers to light used for human activities that brightens the sky and hinders astronomical observations. D) Light pollution refers to the lights that must be used inside major observatories and that make it difficult for astronomers' eyes to adapt to darkness. E) Light pollution is another name for sunlight, which makes it impossible to see stars in the daytime.

C) Light pollution refers to light used for human activities that brightens the sky and hinders astronomical observations.

Why do astronomers need different telescope designs to observe across the electromagnetic spectrum? A) New telescopes incorporate new technology to increase their efficiency. B) Telescopes have to adapt to the greater distortion of the atmosphere at shorter wavelengths. C) Photons of different energy behave differently and require different collection strategies. D) Light pollution is worse at radio wavelengths than visible wavelengths. E) Astronomers and engineers enjoy the challenge of making new telescope designs.

C) Photons of different energy behave differently and require different collection strategies.

The angular separation of two stars is 0.1 arcseconds and you photograph them with a telescope that has an angular resolution of 1 arcsecond. What will you see? A) The two stars will appear to be touching, looking rather like a small dumbbell. B) The stars will not show up at all in your photograph. C) The photo will seem to show only one star rather than two. D) You will see two distinct stars in your photograph.

C) The photo will seem to show only one star rather than two.

Which of the following best describes the development of astronomical telescopes over the past 60 years? A) Over the 60-year period, telescopes have gradually gotten bigger and more powerful. B) Although there have been advances in cameras and computing power, telescopes themselves have not changed much in the last 60 years. C) The world's most powerful telescope remained the same for most of this period, but in the past 20 years many new and more powerful telescopes have been built. D) The only major change in telescope power has occurred because of our ability to launch telescopes into space rather than operating them only from the ground.

C) The world's most powerful telescope remained the same for most of this period, but in the past 20 years many new and more powerful telescopes have been built.

What is the angular resolution of the human eye? A) about 1 degree B) about 1 arcsecond (1/3600 of a degree) C) about 1 arcminute, or 1/60 of a degree D) about 1 milliarcsecond

C) about 1 arcminute, or 1/60 of a degree

Consider an atom of oxygen in which the nucleus contains 8 protons and 8 neutrons. If it is doubly ionized, what is the charge of the oxygen ion and how many electrons remain in the ion?

Charge = +2; number of remaining electrons = 6.

Following are the different layers of the Sun's atmosphere. Rank them based on the order in which a probe would encounter them when traveling from Earth to the Sun's surface, from first encountered to last. Corona chromosphere photosphere

Corona chromosphere photosphere

Rank the layers of the Sun's atmosphere based on their temperature, from highest to lowest Corona chromosphere photosphere

Corona chromosphere photosphere Scientists were quite surprised when they first learned that the temperature increases with altitude in the Sun's atmosphere, and even today the heating mechanism is not fully understood. However, we know that magnetic fields play an important role in transporting heat upward, making the chromosphere hotter than the photosphere and the corona hotter still.

Rank the layers of the atmosphere based on the energy of the photons that are typically emitted there, from highest to lowest. Corona chromosphere photosphere

Corona chromosphere photosphere The energy of the emitted light rises with temperature, so the ranking for this question is the same as that of Part C. In fact, the photosphere emits primarily visible light, the chromosphere primarily ultraviolet light, and the corona primarily X rays. This is why astronomers study the corona with X-ray telescopes and the chromosphere with ultraviolet telescopes, while we observe the photosphere with visible-light telescopes.

Currently, the largest optical telescope mirrors have a diameter of A) 1 m. B) 2 m. C) 5 m. D) 10 m. E) 100 m.

D) 10 m.

What do we mean by the diffraction limit of a telescope? A) It is the maximum size to which any telescope can be built. B) It describes the farthest distance to which the telescope can see. C) It describes the maximum exposure time for images captured with the telescope. D) It is the best angular resolution the telescope could achieve with perfect optical quality and in the absence of atmospheric distortion.

D) It is the best angular resolution the telescope could achieve with perfect optical quality and in the absence of atmospheric distortion.

Which of the following statements about light focusing is not true? A) In a healthy eye, light is focused on the retina. B) Film should be placed at the focal plane in a camera. C) If you try to look at an image that is not formed at the focal plane, it will be blurry. D) The focal plane of a reflecting telescope is always located within a few inches of the primary mirror.

D) The focal plane of a reflecting telescope is always located within a few inches of the primary mirror.

Which of the following is always true about images captured with X-ray telescopes? A) They are always very pretty. B) They are always displayed with the highest possible angular resolution. C) They are always useful for seeing through things. D) They are always displayed in false color. E) They are always displayed with north pointing upward in the images.

D) They are always displayed in false color.

What causes stars to twinkle? A) It is intrinsic to the stars—their brightness varies as they expand and contract. B) variations in the absorption of the atmosphere C) variable absorption by interstellar gas along the line of sight to the star D) bending of light rays by turbulent layers in the atmosphere E) the inability of the human eye to see faint objects

D) bending of light rays by turbulent layers in the atmosphere

Which of the following wavelength regions cannot be studied with telescopes on the ground? A) radio waves B) ultraviolet C) X rays D) both B and C E) both A and C

D) both B and C

Suppose you want to determine the chemical composition of a distant planet or star. Which of the following will be most useful to have? A) high angular resolution B) high turbulence C) a radio telescope D) high spectral resolution

D) high spectral resolution

Which of the following is not a good reason to place observatories on remote mountain tops? A) to reduce light pollution B) to reduce light distortion C) to reduce light absorption D) to be able to observe at radio wavelengths E) to be able to observe at infrared wavelengths

D) to be able to observe at radio wavelengths

If our eyes were sensitive only to X rays, the world would appear

Dark because X-ray light does not reach Earth's surface

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

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

The largest effective telescope, created by radio interferometry, is the size of A) several football fields, in a natural depression in Puerto Rico. B) tens of miles across, in the deserts of New Mexico. C) the state of New Mexico. D) the continental United States. E) Earth.

E) Earth.

Which of the following could not be determined by an observation that uses only spectroscopy? A) the chemical composition of a distant star B) the speed at which a distant galaxy is moving away from us C) the surface temperature of a distant star D) the rotation rate of a distant star E) the size of a distant galaxy

E) the size of a distant galaxy

An astronomical unit is

Earth's average distance from the Sun

Which of the following statements about electrons is not true? Within an atom, an electron can have only particular energies. Electrons have very little mass compared to protons or neutrons. Electrons orbit the nucleus rather like planets orbiting the Sun. An electron has a negative electrical charge. Electrons can jump between energy levels in an atom only if they receive or give up an amount of energy equal to the difference in energy between the energy levels.

Electrons orbit the nucleus rather like planets orbiting the Sun.

Because gamma rays have very short wavelengths, gamma-ray telescopes can achieve extremely high angular resolution

False

Professional astronomical telescopes generally have a much greater magnification than the telescopes you can buy in stores.

False

The term seeing is used to describe how faint an object can be detected by a telescope

False

Which of the following is not one of the three main categories of observation generally used by astronomers?

Filtering to look at just a single color from an object.

Earth is stationary at the center of the universe

For most of history, the lack of observable stellar parallax was interpreted to mean that _________.

How much greater is the light-collecting area of a 6-meter telescope than a 3-meter telescope?

Four times

When the temperature of the Sun's core goes down, what happens next? Fusion reactions speed up; the core expands and cools. Fusion reactions slow down; the core expands and heats. Fusion reactions slow down; the core shrinks and heats. Fusion reactions speed up; the core shrinks and cools.

Fusion reactions slow down; the core shrinks and heats.

How are galaxies important to our existence?

Galaxies recycle material from one generation of stars to the next, and without this recycling we could not exist.

the four seasons would each be twice as long as they are now

If our year were twice as long (that is, if Earth took twice as many days to complete each orbit around the Sun), but Earth's rotation period and axis tilt were unchanged, then _________.

Which of the following must occur for a star's core to reach equilibrium after an initial change in fusion rate? Check all that apply. If the fusion rate initially decreases, then the core expands. If the fusion rate initially increases, then the core expands. If the fusion rate initially decreases, then the core contracts. If the fusion rate initially increases, then the core contracts.

If the fusion rate initially increases, then the core expands. If the fusion rate initially decreases, then the core contracts. Increasing the fusion rate releases more energy into the core, which raises the temperature and increases the internal pressure, causing the core to expand. Decreasing the fusion rate means less energy is released, so the temperature and internal pressure decreases. As you can see in the interactive figure, the solar thermostat keeps the fusion rate fairly steady in a star like the Sun because a temperature increase causes the core to expand while a temperature decrease causes the core to contract.

Part A Sort each of the astronomical questions below into the appropriate bin based on the type of observation you would need to perform to answer it.

Imaging: How large is the Andromeda Galaxy? What are the major surface features of Mars? Are stars in the Orion Nebula surrounded by gas? Spectroscopy: What is the chemical composition of the Crab Nebula? What is the temperature of Jupiter's atmosphere? Is the star Vega moving toward us or away from us? Timing: Does the star Mira vary in brightness? Is the X-ray emission from the galactic center steady or changing?

One of the first steps is to choose what type of observation to make. Recall that three basic types of astronomical observation are imaging (taking a photograph of an object), spectroscopy (spreading an object's light into a spectrum), and timing (measuring how an object's light varies with time). ---Sort each of the astronomical questions below into the appropriate bin based on the type of observation you would need to perform to answer it.

Imaging= how large is the andromeda galaxy? =are stars in the Orion Nebula surrounded by dusty disks of gas? =what are the major surface features of mars? Spectroscopy= what is the temperature of Jupiter's atmosphere? =is the star Vega moving toward us or away from us? =what is the chemical composition of the Crab Nebula? Timing= does the star Mira vary in brightness? =is the x-ray emission from the galactic center steady or changing?

Where should you put a telescope designed for ultraviolet observations?

In Earth orbit

our evening view of space depends on where Earth is located in its orbit around the Sun

In any particular place on Earth, certain constellations are visible in the evening only at certain times of the year because _________.

If you had only one telescope and wanted to take both visible-light and ultraviolet pictures of stars, where should you locate your telescope?

In space

Different telescopes are optimized for observing different wavelengths of light, so another consideration in planning an observation is deciding what type of telescope to use.---Each of the following statements describes an astronomical measurement. Place each measurement into the appropriate bin based on the type of telescope you would use to make it.

Infrared Telescopes= determine the surface temperature of Venus. = study a dense cloud of cold gas in space. Visible Light Telescope= measure the brightness of a star that is similar to our Sun. = Obtain a spectrum of sunlight reflected by Mars. X-Ray Telescope= observe the hot (1-million K) gas in the Sun's corona. =look for high-energy radiation from a supernova. (Cool objects emit in the infrared. The Sun and similar stars emit mostly in the visible; reflected light from Mars is therefore also visible light. Very hot gas emits X rays, which have very high energy (with only gamma-ray photons having more energy for light)).

The James Webb Space Telescope is designed primarily to observe __________

Infrared light

Part B Each of the following statements describes an astronomical measurement. Place each measurement into the appropriate bin based on the type of telescope you would use to make it.

Infrared telescope: Determine the surface temperature of Venus. Steady a dense cloud of cold gas in space. Visible Light telescope: Obtain a spectrum of the sunlight reflected by Mars. Measure the brightness of a star that is similar to our Sun. X-ray telescope: Observe the hot (1-million K) gas in the Sun's corona. Look for high-energy radiation from a supernova.

Which of the following statements is true of green grass?

It absorbs red light and reflects green light.

Relative to the age of the universe, how old is our solar system?

It is about one-third the age of the universe.

Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes?

It is closer to the stars.

Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes? It never has to close because of cloudy skies. It is closer to the stars. Stars do not twinkle when observed from space. It can observe infrared and ultraviolet light, as well as visible light.

It is closer to the stars. Distance to the stars has absolutely nothing to do with it, as should be apparent if you consider the scale of the solar system and the distances to stars to scale (as discussed in Chapter 1).

Figure showing a laboratory spectrum on the top and four object spectra underneath. Consider the spectra of the four objects shown beneath the laboratory spectrum. Based on these spectra, what can you conclude about Object 1? It is a star with a thin upper atmosphere. It is a very hot object, with a temperature above 1 million K. It is composed mostly of hydrogen, helium, and iron. It is moving toward us. It is moving away from us.

It is moving toward us Notice that the lines in Object 1's spectrum are all to the right of those in the laboratory spectrum. You can tell that this indicates a redshift - which means the object is moving away - because red is on the right side of these spectra (and blue is on the left).

What do we mean by the diffraction limit of a telescope?

It is the angular resolution the telescope could achieve if nothing besides the size of its light-collecting area affected the quality of its images.

Which of the following best describes what we mean by the focal plane of a telescope?

It is the place where, if we mounted film or an electronic detector, we could get a clear (not blurry) image of an object viewed through the telescope.

What is the purpose of adaptive optics?

It reduces blurring caused by atmospheric turbulence for telescopes on the ground.

Suppose you had molecular oxygen (O2) chilled enough so that it was in liquid form. Which of the following best describes the phase changes that would occur as you heated the liquid oxygen to high temperature?

It would evaporate into a gas, then the molecules would dissociate into individual oxygen atoms, then the atoms would become increasingly ionized as you continued to raise the temperature.

third quarter

It's 6 am and the Moon is at its highest point in your sky (crossing the meridian). What is the Moon's phase?

Betelgeuse is the bright red star representing the left shoulder of the constellation Orion. All the following statements about Betelgeuse are true. Which one can you infer from its red color?

Its surface is cooler than the surface of the Sun.

Betelgeuse is the bright red star representing the left shoulder of the constellation Orion. All the following statements about Betelgeuse are true. Which one can you infer from its red color? It is much more massive than the Sun. Its surface is cooler than the surface of the Sun. It is much brighter than the Sun. It is moving away from us.

Its surface is cooler than the surface of the Sun. Red light has lower energy than yellow or white light, so the red color of Betelgeuse tells us that its peak thermal radiation comes at lower energy than the peak thermal radiation of the yellow/white Sun. A lower energy of peak radiation means a lower temperature.

What do astronomers mean by light pollution?

Light pollution is light from human sources that makes it difficult to see the stars at night.

If we double the diameter of a telescope's mirror, what happens to its light-gathering ability?

Light-gathering ability quadruples

Consider two future observatories in space. Observatory X consists of a single 50-meter telescope. Observatory Y is an interferometer consisting of five 10-meter telescopes, spread out over a region 100 meters across. Which observatory can detect dimmer stars, and which one can see more detail in its images? (Assume all else is equal, such as quality of optics, types of instruments, and so on.

Observatory X can detect dimmer stars and Observatory Y reveals more detail in images.

Suppose that two stars are separated in the sky by 0.1 arcsecond. If you look at them with a telescope that has an angular resolution of 0.5 arcsecond, what will you see?

One point of light that is the blurred image of both stars.

How long does it take the Earth to complete one orbit around the Sun?

One year

Radio telescopes would NOT represent a good choice for astronomical study of ________

Ordinary stars

What is the difference between energy and power?

Power is the rate at which energy is used, so its units are a unit of energy divided by a unit of time.

What is meant in astronomy by the phrase "adaptive optics"?

Rapid modifications are made to the tilt and location of the elements of a telescope to correct for the effects of atmospheric and instrumental distortion

The primary reason professional observatories are built on the highest mountaintops is to

Reduce atmospheric blurring

Listed following are distinguishing characteristics and examples of reflecting and refracting telescopes. Match these to the appropriate category. Reflecting Telescopes: Refracting Telescopes: The world's largest is 1-meter in diameter, most commonly used by professional astronomers today, very large telescopes become "top- heavy", The Hubble Space Telescope, world's largest telescope, incoming light passes through glass

Reflecting Telescopes: most commonly used by professional astronomers today, The Hubble Space Telescope, world's largest telescope Refracting Telescopes: The world's largest is 1-meter in diameter, Galileo's telescopes, very large telescopes become "top- heavy", incoming light passes through glass

Where is our solar system located within the Milky Way Galaxy?

Roughly halfway between the center and the edge of the visible disk of the galaxy

Suppose you built a scale-model atom in which the nucleus is the size of a tennis ball. About how far would the cloud of electrons extend?

Several kilometers

If you could count stars at a rate of about one per second, how long would it take to count all the stars in the Milky Way Galaxy?

Several thousand years

Astronomical sources emit electromagnetic radiation at various wavelengths. Some sources might emit just visible and infrared radiation. Other sources might emit gamma, UV, visible, and infrared radiation. Some of that radiation travels in the direction of Earth and can be detected with the right telescopes placed in the right locations. Some wavelengths can be read in the atmosphere. However, the majority of wavelengths are either read from space or Earth's surface. Which observations would require you to launch a telescope above the Earth's atmosphere? Please drag each observing mode below into either the ground-based (Surface) zone or space-borne (Space) zone, depending on the respective observing requirements.

Space Zone: - Far-infrared observations - Gamma-ray observations - X-ray observations - Far-ultraviolet observations Surface Zone: - Visible observations - Radio observations

_____________ separate the various colors of light, allowing astronomers to determine stellar composition and many other stellar properties.

Spectrographs

Suppose that Star X and Star Y both have redshifts, but Star X has a larger redshift than Star Y. What can you conclude? Star X is moving away from us faster than Star Y. Star X is coming toward us faster than Star Y. Star X is moving away from us and Star Y is moving toward us. Star Y is moving away from us faster than Star X. Star X is hotter than Star Y.

Star X is moving away from us faster than Star Y. The redshifts mean that both stars are moving away from us, and a larger redshift means a faster speed.

Which of the following is a general difference between a planet and a star?

Stars glow in infrared and visible light, while planets glow only in the infrared.

Which of the following studies is best suited to astronomical observations that fall into the category called time monitoring?

Studying how a star's brightness varies over a period of 3 years.

The length of each season (for example, the number of days from the summer solstice to the fall equinox) would be significantly longer than it is now.

Suppose Earth's axis tilt was significantly greater than its current 23.5 degrees, but Earth's rotation period and orbital period were unchanged. Which statement below would not be true?

new Earth

Suppose it is full Moon. What phase of Earth would someone on the Moon see at this time?

To the right of Polaris; that is, 90 degrees counterclockwise from its current position

Suppose you are facing north and you see the Big Dipper close to your northern horizon, with Polaris (and the Little Dipper) above it. Where will you see the Big Dipper in six hours?

Your friend will also see a crescent moon.

Suppose you live in the United States and you see a crescent moon in your evening sky tonight. What will a friend in South America see tonight?

the Galileo spacecraft that orbited Jupiter in the 1990s

Suppose you see a photo showing Jupiter half in sunlight and half in shadow (that is, a first quarter Jupiter). This photo might have been taken by _________.

latitude 40 degrees south

Suppose you use the Southern Cross to determine that the south celestial pole appears 40 degrees above your horizon. Then you must be located at _________.

Which of the following statements best describes the two principle advantages of telescopes over eyes?

Telescopes can collect far more light with far better angular resolution.

How does the light-collecting area of an 8-meter telescope compare to that of a 2-meter telescope? The 8-meter telescope has 8 times the light-collecting area of the 2-meter telescope. The answer cannot be determined from the information given in the question. The 8-meter telescope has 16 times the light-collecting area of the 2-meter telescope. The 8-meter telescope has 4 times the light-collecting area of the 2-meter telescope.

The 8-meter telescope has 16 times the light-collecting area of the 2-meter telescope. The 8-meter telescope is 4 times larger in diameter, so its light collecting area is 42 = 16 times greater.

We could not see it at all.

The Andromeda Galaxy is faintly visible to the naked eye in the constellation Andromeda. Suppose instead it were located in the same direction in space as the center of the Milky Way Galaxy (but still at its current distance). How would it appear to the eye in that case?

Which of the following telescopes benefits most from adaptive optics?

The Keck I telescope on Mauna Kea

Which of the following statements is an inference from a model (rather than an observation)? The photosphere emits visible light. The photosphere is made out of mainly hydrogen and helium. The Sun's core is gradually turning hydrogen into helium. The Sun emits neutrinos. The corona is hotter than the photosphere.

The Sun's core is gradually turning hydrogen into helium.

Which statement about motion in the universe is not true?

The mysterious dark matter is the fastest-moving material in the universe.

What would happen if the fusion rate in the core of the Sun were increased but the core could not expand? The Sun's core would start to cool down and the rate of fusion would decrease. The Sun's core would reach a new equilibrium at a lower temperature. The Sun's core would reach a new equilibrium at a higher temperature. The Sun's core would start to heat up and the rate of fusion would increase even more.

The Sun's core would start to heat up and the rate of fusion would increase even more As you know from Part B, an increase in the fusion rate will cause the core to expand in a normal (or main-sequence) star like the Sun, and this expansion will restore core equilibrium. But if for some reason the core could not expand, the higher temperature would make the fusion rate increase even more, creating a positive feedback loop in which the fusion rate and temperature would keep getting higher and higher. (That is, there would be no equilibrium.) In fact, as you'll learn when you study stellar life cycles, this is essentially what will occur when the Sun is near the end of its life.

the spring and fall equinoxes

The Sun's path, as viewed from the equator, is highest in the sky on _________.

What does angular resolution measure?

The angular size of the smallest features that the telescope can see.

Consider an atom of gold in which the nucleus contains 79 protons and 118 neutrons. What is its atomic number and atomic mass number? The atomic number is 118, and the atomic mass number is 197. The atomic number is 79, and the atomic mass number is 197. The atomic number is 118, and the atomic mass number is 79. The atomic number is 79, and the atomic mass number is 118.

The atomic number is 79, and the atomic mass number is 197.

astronomical unit (au)

The average distance (semimajor axis) of Earth from the Sun, which is about 150 million km.

astronomical unit (AU)

The average distance between Earth and the Sun, which is about 150 million kilometers. More technically, 1 AU is the length of the semimajor axis of Earth's orbit.

When we say the universe is expanding, we mean that:

The average distance between galaxies is growing with time

Suppose you see two stars: a blue star and a red star. Which of the following can you conclude about the two stars? Assume that no Doppler shifts are involved. (Hint: Think about the laws of thermal radiation.) The blue star has a hotter surface temperature than the red star. The red star has a hotter surface temperature than the blue star. The blue star is more massive than the red star. The red star is more massive than the blue star. The blue star is farther away than the red star.

The blue star has a hotter surface temperature than the red star.

Which of the following conditions lead you to see an absorption line spectrum from a cloud of gas in interstellar space?

The cloud is cool and lies between you and a hot star.

Which of the following conditions lead you to see an absorption line spectrum from a cloud of gas in interstellar space? The cloud is cool and very dense, so that you cannot see any objects that lie behind it. The cloud is cool and lies between you and a hot star. The cloud is extremely hot. The cloud is visible primarily because it reflects light from nearby stars.

The cloud is cool and lies between you and a hot star. Atoms or molecules in the cloud therefore absorb specific wavelengths of light from the hot star.

The visible spectrum of the Sun. This photo shows the visible light spectrum of the Sun. Why does it have all those dark lines on it? The dark lines are caused by Doppler shifts. The dark lines represent wavelengths of light at which atoms near the Sun's surface absorb radiation from the hotter solar interior. The dark lines are not real, but rather are artifacts of the photographic process used to record the spectrum. The dark lines come from sunspots on the Sun, which are dark in color.

The dark lines represent wavelengths of light at which atoms near the Sun's surface absorb radiation from the hotter solar interior. In other words, the Sun has an absorption line spectrum because its surface (photosphere) acts like a cooler cloud over the much hotter interior.

light-year (ly)

The distance that light can travel in 1 year, which is 9.46 trillion km.

light-year

The distance that light can travel in 1 year, which is about 10 trillion kilometers (more precisely, 9.46 trillion km).

The diagram represents energy levels in a hydrogen atom. The labeled transitions (A through E) represent an electron moving between energy levels. Suppose that an electron in a hydrogen atom absorbs 10.2 eV of energy, so that it moves from level 1 to level 2. What typically happens next? The electron remains in level 2 until it absorbs an additional 10.2 eV of energy. The electron jumps to level 3 as soon as it absorbs any additional energy. The electron returns to level 1 by emitting an ultraviolet photon with 10.2 eV of energy. A different electron drops into level 1, since it is now unoccupied.

The electron returns to level 1 by emitting an ultraviolet photon with 10.2 eV of energy.

Suppose that two stars are identical in every way - for example, same distance, same mass, same temperature, same chemical composition, and same speed relative to Earth - except that one star rotates faster than the other. Spectroscopically, how could you tell the stars apart?

The faster rotating star has wider spectral lines than the slower rotating star.

You observe a distant galaxy. You find that a spectral line of hydrogen that is shifted from its normal location in the visible part of the spectrum into the infrared part of the spectrum. What can you conclude?

The galaxy is moving away from you.

Which of the following best describes why we say that light is an electromagnetic wave? Which of the following best describes why we say that light is an electromagnetic wave? Light is produced only when massive fields of electric and magnetic energy collide with one another. The term electromagnetic wave arose for historical reasons, but we now know that light has nothing to do with either electricity or magnetism. Light can be produced only by electric or magnetic appliances. The passage of a light wave can cause electrically charged particles to move up and down.

The passage of a light wave can cause electrically charged particles to move up and down.

orbit

The path followed by a celestial body because of gravity; an orbit may be bound (elliptical) or unbound (parabolic or hyperbolic).

The angular separation of two stars is 0.1 arcseconds and you photograph them with a telescope that has an angular resolution of 1 arcsecond. What will you see? The photo will seem to show only one star rather than two. The stars will not show up at all in your photograph. The two stars will appear to be touching, looking rather like a small dumbbell. You will see two distinct stars in your photograph

The photo will seem to show only one star rather than two. Because the angular separation of the stars is smaller than the telescope's angular resolution, the light of the two stars will be blurred together to look like a single star.

What is the ecliptic plane?

The plane of Earth's orbit around the Sun

ecliptic plane

The plane of Earth's orbit around the Sun.

If we observe one edge of a planet to be redshifted and the opposite edge to be blueshifted, what can we conclude about the planet?

The planet is rotating.

If we observe one edge of a planet to be redshifted and the opposite edge to be blueshifted, what can we conclude about the planet? The planet is actually two bodies, one moving toward us, the other away from us. The planet is in the process of falling apart. The planet is in the process of formation. The planet is rotating.

The planet is rotating.

Suppose we make a scale model of our solar system, with the Sun the size of a grapefruit. Which of the following best describes what the planets would look like?

The planets are all much smaller than the Sun. Four planets are within about 20 meters of the Sun, while the rest planets are spread much farther apart.

observable universe

The portion of the entire universe that can be seen from Earth, at least in principle. The observable universe is probably only a tiny portion of the entire universe.

observable universe

The portion of the entire universe that, at least in principle, can be seen from Earth.

nuclear fusion

The process in which two (or more) smaller nuclei slam together and make one larger nucleus.

Suppose you are listening to a radio station that broadcasts at a frequency of 97 Mhz (megahertz). Which of the following statements is true?

The radio waves from the radio station are causing electrons in your radio's antenna to move up and down 97 million times each second.

An image showing two stars. An image showing one star. The first telescopic photo shows what appears to be a single star. The second photo shows the same object, now revealed to be two distinct stars. What is the difference between the two photos? The second photo was taken by two telescopes rather than one. The second photo was taken with a telescope that has greater light-collecting area. The second photo has better (smaller) angular resolution than the first photo. The second photo comes from a radio telescope while the first photo comes from a visible-light photo.

The second photo has better (smaller) angular resolution than the first photo. Better angular resolution means we can see (resolve) the two individual sources that are blurred together in the first photo.

rotation

The spinning of an object around its axis.

rotation

The spinning of an object around its axis. For example, Earth rotates once each day around its axis, which is an imaginary line connecting the North and South Poles.

Laboratory measurements show hydrogen produces a spectral line at a wavelength of 486.1 nanometers (nm). A particular star's spectrum shows the same hydrogen line at a wavelength of 486.0 nm. What can we conclude?

The star is moving toward us.

Laboratory measurements show hydrogen produces a spectral line at a wavelength of 486.1 nanometers (nm). A particular star's spectrum shows the same hydrogen line at a wavelength of 486.0 nm. What can we conclude? The star is moving away from us. The star is moving toward us. The star is getting hotter. The star is getting colder.

The star is moving toward us. The wavelength is shifted from 486.1 to 486.0 nm, which means a shift to a shorter wavelength. A shorter wavelength means a shift to the blue end of the spectrum (a blueshift) so that the object is moving toward us.

Which of the following best describes what we mean by the universe?

The sum total of all matter and energy

universe

The sum total of all matter and energy.

Studying a spectrum from a star can tell us a lot. All of the following statements are true except one. Which statement is not true? We can identify chemical elements present in the star by recognizing patterns of spectral lines that correspond to particular chemicals. The total amount of light in the spectrum tells us the star's radius. Shifts in the wavelengths of spectral lines compared to the wavelengths of those same lines measured in a laboratory on Earth can tell us the star's speed toward or away from us. The peak of the star's thermal emission tells us its temperature: hotter stars peak at shorter (bluer) wavelengths.

The total amount of light in the spectrum tells us the star's radius. We cannot measure radius from a spectrum without additional information.

The planet Neptune is blue in color. How would you expect the spectrum of visible light from Neptune to be different from the visible-light spectrum of the Sun?

The two spectra would have similar shapes, except Neptune's spectrum would be missing a big chunk of the red light that is present in the Sun's spectrum.

The fact that nearly all galaxies are moving away from us, with more distant ones moving faster, helped us to conclude that:

The universe is expanding

Which of the following is always true about images captured with X-ray telescopes?

They are always shown with colors that are not the true colors of the objects that were photographed.

Which of the following is always true about images captured with X-ray telescopes? They are always very pretty. They always are made with adaptive optics. They show us light with extremely long wavelengths compared to the wavelengths of visible light. They always have very high angular resolution. They are always shown with colors that are not the true colors of the objects that were photographed.

They are always shown with colors that are not the true colors of the objects that were photographed. "True colors" make sense only for visible light, not X rays.

Suppose you watch a leaf bobbing up and down as ripples pass it by in a pond. You notice that it does two full up and down bobs each second. Which statement is true of the ripples on the pond? They have a frequency of 2 hertz. They have a frequency of 4 hertz. They have a wavelength of two cycles per second. We can calculate the wavelength of the ripples from their frequency.

They have a frequency of 2 hertz - Remember that hertz are units meaning "cycles per second."

Suppose you watch a leaf bobbing up and down as ripples pass it by in a pond. You notice that it does two full up and down bobs each second. Which statement is true of the ripples on the pond?

They have a frequency of 2 hertz.

Which of the following best describes the fundamental difference between two different chemical elements (such as oxygen and carbon)?

They have different numbers of protons in their nucleus.

Radio telescopes are large in part to improve their angular resolution, which is poor because of the long wavelengths at which they are used to observe the skies

True

The lens in your eye forms an upside-down image of the world.

True

Suppose you decide to make a graph of intensity against wavelength for the spectrum shown here. Which of the following shows what the graph will look like?

Upside down spike wavelength graph Notice that the downward spikes on the graph occur at wavelengths corresponding to the dark lines in the spectrum.

milky way

Used both as the name of our galaxy and to refer to the band of light we see in the sky when we look into the plane of our galaxy.

Which of the following forms of light can be observed with telescopes at sea level?

Visible light Radio waves

Which of the following correctly describes how the process of gravitational contraction can make a star hot? Gravitational contraction involves the generation of heat by chemical reactions, much like the burning of coal. When a star contracts in size, gravitational potential energy is converted to thermal energy. Gravitational contraction involves nuclear fusion, which generates a lot of heat. Heat is generated when gravity contracts, because gravity is an inverse square law force.

When a star contracts in size, gravitational potential energy is converted to thermal energy.

higher in the sky

When traveling north from the United States into Canada, you'll see the North Star (Polaris) getting _________.

The "celestial sphere" is another name for our universe.

Which of the following statements about the celestial sphere is NOT true?

When did humans learn that the Earth is not the center of the universe?

Within the past 500 years

Why can't X-ray and gamma-ray telescopes use the same designs as visible-light telescopes?

X rays and gamma rays have so much energy that they cannot be reflected in the same way as visible light.

The Chandra X-ray Observatory must operate in space because:

X rays do not penetrate Earth's atmosphere.

The Chandra X-ray Observatory must operate in space because: X rays do not penetrate Earth's atmosphere. X-ray telescopes require the use of grazing incidence mirrors. It was built by NASA. X rays are too dangerous to be allowed on the ground.

X rays do not penetrate Earth's atmosphere. To detect X rays, the observatory must be above Earth's atmosphere.

Which of the following statements about X rays and radio waves is not true?

X rays travel through space faster than radio waves.

Which of the following statements about X rays and radio waves is not true? X rays travel through space faster than radio waves. X rays have higher frequency than radio waves. X rays and radio waves are both forms of light, or electromagnetic radiation. X rays have shorter wavelengths than radio waves.

X rays travel through space faster than radio waves.

A full moon high in the sky

You observe a full Moon rising at sunset. What will you see at midnight?

Which of the following has your "cosmic address" in the correct order?

You, Earth, solar system, Milky Way Galaxy, Local Group, Local Supercluster, universe

Consider a raisin cake expanding uniformly in an oven. Viewed from one of the raisins, you would see _____.

all other raisins moving away from you, with more distant raisins moving faster

Visible light from a distant star can be spread into a spectrum by using a glass prism or ______.

a diffraction grating

The number of stars in the Milky Way Galaxy is approximately _________.

a few hundred billion

No object produces a perfect thermal radiation spectrum, but many objects produce close approximations. Which of the following would not produce a close approximation to a thermal radiation spectrum?

a hot, thin (low-density, nearly transparent) gas

According to the laws of thermal radiation, hotter objects emit photons with _________.

a shorter average wavelength

What is the angular resolution of the human eye?

about 1 arcminute, or 1/60 of a degree

A light-year is _________.

about 10 trillion kilometers

This Figure showing blackbody curves for several stars and a human. This figure shows idealized thermal radiation spectra from several stars and a human. Based on this graph, at about what wavelength does a 15,000 K star emit its most intense light? about 20 nanometers about 100 nanometers About 100,000 nanometers about 1,000 nanometers

about 100 nanometers The blue curve represents the 15,000 K star and it peaks close to 102 = 100 nm on the wavelength axis.

The Hubble Space Telescope obtains higher-resolution images than most ground-based telescopes because it is: larger. closer to the stars. above Earth's atmosphere.

above Earth's atmosphere.

If we say that a material is opaque to ultraviolet light, we mean that it _________.

absorbs ultraviolet light

Astronomers infer that the universe is expanding because distant galaxies all appear to

be moving away from us, with more distant ones moving faster

Astronomers infer that the universe is expanding because distant galaxies all appear to _________.

be moving away from us, with more distant ones moving faster

Rank the layers of the Sun's atmosphere based on their density, from highest to lowest. Corona chromosphere photosphere

photosphere chromosphere corona As your answer correctly indicates, the density of the Sun's atmosphere decreases with altitude above the photosphere.

Most of the Sun's ultraviolet light is emitted from the narrow layer called the ______ where temperature increases with altitude.

chromosphere

A typical galaxy is a _________.

collection of a few hundred million to a trillion or more stars, bound together by gravity

Energy moves through the sun's _____ by means of the rising of hot gas and falling of cooler gas.

convection zone

Nuclear fusion of hydrogen into helium occurs in the _____.

core

we can see the sun's ______ most easily during total solar eclipses

corona

If our eyes were sensitive only to X rays, the world would appear __________. If our eyes were sensitive only to X rays, the world would appear __________. gray, black, and white like a medical X ray brighter than normal because X rays carry more energy than visible light photons dark because X-ray light does not reach Earth's surface green, yellow, and orange, because those are the colors of X rays

dark because X-ray light does not reach Earth's surface Because X rays from the Sun do not reach Earth's surface, eyes that were sensitive only to X rays would have nothing to see.

The Earth rotates one a _ on its acis and orbits the Sun once each _ The eliptic plane is the plane defines by _ 's orbit around _. Axis tolt of a planet is the amount that _ is tipped relative to a line perpendicular to the ecliptic plane.

day, year, Earth, the Sun, its axis

How do we know how old the Sun is? from Newton's version of Kepler's third law and the orbits of the planets from its speed and distance from us from ages of solar system meteorites, based on radioactive elements from calculating its fuel supply and how fast it is using it up

from ages of solar system meteorites, based on radioactive elements

From shortest to longest wavelength, which of the following correctly orders the different categories of electromagnetic radiation?

gamma rays, X rays, ultraviolet, visible light, infrared, radio

What two physical processes balance each other to create the condition known as gravitational equilibrium in stars? the strong force and the electromagnetic force gravitational force and surface tension gravitational force and outward pressure the strong force and the weak force

gravitational force and outward pressure

The spectra of most galaxies show redshifts. This means that their spectral lines _________.

have wavelengths that are longer than normal

In which case will the woman see a just a spectrum that is almost entirely black except for few bright emission lines?

hot, glowing cloud of hydrogen gas The hot cloud emits light only at specific wavelengths, producing an emission line spectrum.

If you had only one telescope and wanted to take both visible-light and ultraviolet pictures of stars, where should you locate your telescope? on Earth's surface on a tall mountain in an airplane in space

in space While visible light can be observed from the ground, ultraviolet light can be easily observed only from space. Indeed, the capability of observing ultraviolet light is a major advantage of the Hubble Space Telescope over larger ground-based telescopes.

The Chandra X-ray observatory focuses x-rays with ___________ mirrors. grazing

incidence

Which forms of light are lower in energy and frequency than the light that our eyes can see?

infrared and radio

The twin 10-m Keck telescopes can work together to obtain better angular resolution through a technique known as ________.

interferometry

An atom that has fewer electrons than protons is called a/an _________.

ion

A television advertisement claiming that a product is light-years ahead of its time does not make sense because

it uses "light-years" to talk about time, but a light-year is a unit of distance

A television advertisement claiming that a product is light-years ahead of its time does not make sense because _________.

it uses "light-years" to talk about time, but a light-year is a unit of distance

Suppose you know the frequency of a photon and the speed of light. What else can you determine about the photon?

its wavelength and energy

A 10-meter telescope has a larger ___________ than a 4-meter telescope.

light-collecting area

Sublimation is the process in which ___________.

molecules go directly from the solid phase to the gas phase

A gas heated to millions of degrees would emit mostly radio waves. an equal amount of all wavelengths of light. mostly X-rays. mostly ultraviolet light. no light, because it is too hot.

mostly X-rays.

The source of energy that keeps the Sun shining today is _________. chemical reactions (fire) nuclear fission gravitational contraction nuclear fusion

nuclear fusion

The age of our solar system is about:

one-third of the age of the universe.

dwarf planet

orbits a star, is large enough for its own gravity to make it round

When considering light as made up of individual "pieces," each characterized by a particular amount of energy, the pieces are called _________.

photons

Which of these layers of the Sun is coolest? core radiation zone photosphere

photosphere

nearly all the visible light we see from the Sun is emitted from the ______

photosphere

What do astronomers mean by the Big Bang?

the event that marked the beginning of the expansion of the universe

The total number of stars in the observable universe is roughly equivalent to

the number of grains of sand on all the beaches on Earth.

If we represent the solar system on a scale that allows us to walk from the Sun to Pluto in a few minutes, then:

the planets would all be marble size or smaller and the nearest stars would be thousands of miles away.

The total number of stars in the observable universe is about

the same as the number of grains of sand on all the beaches on Earth

The total number of stars in the observable universe is about _________.

the same as the number of grains of sand on all the beaches on Earth

Our solar system consists of

the sun and all the objects that orbit it

Suppose you want to know the chemical composition of a distant star. Which piece of information is most useful to you?

the wavelengths of spectral lines in the star's spectrum

Which of the following is not a good reason to place observatories on remote mountain tops? to reduce light distortion to be able to observe at radio wavelengths to reduce light absorption to reduce light pollution

to be able to observe at radio wavelengths

The stars in our sky twinkle in brightness and color because of ______.

turbulence in the Earth's atmosphere

Which of the following effects is caused by atmospheric turbulence?

twinkling of stars