Astronomy 201 Flashcards
Chapters 1-5
From the position of Earth inside the Milky Way Galaxy, humans cannot see through to the far rim of the Galaxy with visible light because:
The space between the stars contains interstellar dust.
Which of the following is equal to 1 astronomical unit (AU)?
The average distance between Earth and the Sun
A reason why the International Date Line bends along the line?
To avoid cutting through groups of islands
X-rays coming from space can only be studied above Earth’s atmosphere because:
they are stopped by the large number of atoms in Earth’s atmosphere with which they interact.
Why do the speeds of the planets of the solar system in their orbits around the Sun vary?
Because of their elliptical orbits
Which of the following statements is true about electromagnetic waves?
They do not require a medium in which to travel.
Which of the following is a necessary condition for a celestial body to be deemed a planet?
It must orbit a star.
Which of the following is a limitation of Kepler’s laws?
They do not help us understand what forces of nature influence planetary motion.
Why do electrons get loose from the ground state, deep inside stars?
Because of the heat inside stars
The Local Group is part of a supercluster of galaxies, called the _____, which stretches over a distance of 110 million light-years.
Virgo Supercluster
For an ellipse, the ratio of the distance between the foci to the length of the major axis is called its _____.
Eccentricity
A difference between planets and stars?
Stars have the ability to consistently produce their own light, whereas planets lack this ability.
According to Niels Bohr, how do electrons remain in orbit around the nuclei?
By only following orbits of certain possible sizes
A reason for the appearance of dark bands in absorption spectra?
Absorption of light at certain frequencies by certain elements
Why was Kepler’s discovery of the elliptical shapes of the orbits of planets a decisive moment in the history of human thought?
Because it demonstrated that an acceptable cosmos could contain a more complex shape like an ellipse, instead of having only circles
The temporary apparent westward motion of a planet observed over the course of many nights as Earth passes between it and the Sun is called _____.
Retrograde motion
The ecliptic is the path _____.
The Sun appears to take around the celestial sphere
A reason atoms are not like a miniature solar system?
The typical atom is far emptier than our solar system out to Neptune.
The reason for Earth’s sky being fairly bright at twilight?
The scattering of sunlight by Earth’s atmosphere when the Sun is below the horizon
The difference between a solar day and a sidereal day?
Sidereal day is defined in terms of the rotation period of Earth with respect to the stars, whereas solar day is defined in terms of the rotation period of Earth with respect to the Sun.
What would occur as the eccentricity of an ellipse approaches one?
The ellipse would become flatter.
The speed needed to make a satellite orbit Earth without being drawn in by the planet’s gravity?
8 km/s
Dark matter
It cannot be directly observed, even with the help of instruments.
The similarity between all types of electromagnetic waves?
They all travel at the same speed in a vacuum.
The ancient Greeks made dedicated efforts to observe stellar parallax, the shift in the apparent direction of a star due to Earth’s orbital motion. However, they were unable to observe stellar paradox because of the:
Large distance between Earth and the stars.
Factors makes the existence of the asteroid belt between Mars and Jupiter possible?
The distance between the two planets
Why is the average Earth-Sun distance called an astronomical unit?
It was the most important measuring standard in the early days of astronomy.
Melanie travels to her friend’s hometown. She goes to the town square that lies at precisely 68 degrees north latitude. Which of the following points in the sky should Melanie look at if she wishes to spot the north celestial pole?
68 degrees above the northern horizon
Right ascension and declination are used by astronomers to
denote the positions of objects in the sky.
The general theory of relativity proposed by Albert Einstein led scientists to:
predict and observe black holes.
The slow and regular change in the direction in which Earth’s axis points is known as _____.
Precession
Each time zone covers _____ of longitude on average.
15 degrees
Ileana witnesses an eclipse for the first time in her life. At noon, she sees the sky getting visibly darker, animals getting really quiet, and she sees some stars for a brief period of time. Which type of eclipse did Ileana witness?
Total solar eclipse
A gas is heated and its temperature increases by 20 degrees Celsius. Which of the following is most likely to occur due to this increase in temperature?
The motion of the atoms will become more rapid.
Stars
All stars will die eventually.
Astronomical unit?
It is the average Earth-Sun distance.
Why do the planets, the Sun, and the Moon always remain within the zodiac?
Because their paths on the celestial sphere lie nearly in the same plane
Electromagnetic waves move through a vacuum by:
producing changing electric and magnetic fields.
Why did Pythagoras suggest that Earth should be a sphere?
Because he believed that the sphere is the perfect form
Why is the color of a star a rough indicator of its temperature?
Because many stars emit in the visible band
Why are certain celestial objects known as fixed stars?
Because they maintain fixed patterns among themselves through many generations
The path of an object through space is called its _____.
Orbit
Which of the following properties make microwaves effective in heating food?
They are absorbed by water molecules
Which of the following necessitated the adoption of standardized time zones?
The advent of faster means of transportation
Why does the Sun rise about four minutes later each day with respect to the stars?
Because of its motion on the ecliptic
The Republic of Maziland launched its first satellite into space. The satellite was launched into low Earth orbit with surgical precision. However, to the dismay of the scientists who worked on this project, the satellite became unstable and was pulled back into Earth’s atmosphere. Which of the following mostly likely caused this mishap?
Frictional drag generated by the swelling of Earth’s atmosphere
Magnetism is caused by _____.
The movement of charged particles
The distance between the Sun and Earth is 149.6 million km. This number is expressed in scientific notation as:
1.496 ×108 km.
To find their way around a multitude of stars in the sky, the ancients found groupings of stars that made some familiar geometric pattern or resembled something they knew. These groupings are known as _____.
constellations
Why do hydrogen atoms only produce dark lines at certain wavelengths in the visible absorption spectrum?
Because they only absorb photons with the exact energy needed to raise electrons to specific orbits
Gideon is traveling from Japan to the United States. When his flight reaches a point above the Pacific Ocean, the passengers are told by the flight crew to decrease the dates on their watches by one day. Which of the following did the airplane just cross?
The International Date Line
The application of Kepler’s first law of planetary motion?
Jupiter’s orbit around the Sun is elliptical.
Strongest argument for Earth not being a disk?
Earth’s shadow on the Moon during a lunar eclipse is always round.
The reason for the retrograde motion of planets observed from Earth?
A difference in orbital speeds between Earth and the other observed planets
A feature of Polaris that distinguishes it from other stars in the sky?
It is in a relatively stable position compared to other stars.
Reason for the speed of light being a natural unit of distance for astronomers?
Information about the universe comes to Earth almost exclusively through various forms of light.
Laws of nature?
The same laws apply everywhere in the universe.
The third quarter of the Moon’s phases when observed from Earth?
Half the Moon is illuminated at this time
The _____ is the nearest large spiral galaxy that is similar to the Milky Way Galaxy.
Andromeda galaxy
What makes Earth wobble on its axis?
Earth’s bulge at the equator
What causes the solar day to be longer than the sidereal day?
The movements of both rotation and revolution of Earth around the Sun
The fact that the Moon always keeps the same face turned toward the Earth is called _____.
Synchronous rotation
The eccentricity of Mars’ orbit is greater than that of Earth’s orbit. Which of the following is a logical conclusion derived from this statement?
Earth’s orbit is more circular than Mars’ orbit.
At a chemical plant, a supervisor instructs his trainee to always view the gauges on the equipment directly and not at an angle. He says that views the gauge at an angle would lead an observer to record a false reading. In this scenario, the supervisor is talking about the concept of _____.
parallax
Why did Aristotle think that the Sun is farther away from Earth than the Moon?
The Moon can block the Sun’s light during solar eclipses.
What would happen to an ellipse if the distance between its foci were reduced to zero?
It would become a circle.
Generally, an atom remains excited for only a very brief time, after which an electron drops back spontaneously to its ground state with _____.
the simultaneous emission of a photon
Why is the Sun’s annual path in the sky not aligned with Earth’s equator?
Because of the tilt in Earth’s axis
Which of the following is a result of the differential forces by the Moon?
Stretching of Earth
Electromagnetic waves?
They do not require a medium in which to travel.
what complicated Ptolemy’s model of the solar system?
He had assumed that all celestial motion had to be in circles.
Asterism
It is an especially noticeable star pattern within a constellation.
How do the orbits of asteroids differ from those of comets?
Asteroids have orbits with smaller semimajor axes than do comets.
why two objects of equal volumes may differ in their masses?
Differing densities
Electromagnetic radiation with the shortest wavelengths is categorized as _____.
Gamma rays
When seen from Earth, _____ occur when the Sun and the Moon are perfectly aligned in the sky but the Moon appears slightly smaller than the Sun due to being at apogee.
annular eclipses
When observed from a city on Earth, the lunar phase called new moon happens when the Moon:
Is in the same general direction in the sky as the Sun.
The assertions made by Nicolaus Copernicus regarding the apparent motion of the Sun about Earth during the course of a year.
It could be represented equally well by a motion of Earth about the Sun.
Using scientific notation to describe numbers is very appealing because it eliminates the:
many zeros that can seem overwhelming to a reader.
The inverse square law for light propagation indicates that:
The apparent brightness of a source of light gets weaker with distance.
Neap tides on Earth occur when the:
Moon is in its first or third quarter.
an important problem in describing scientific models in the field of astronomy?
Words are often unable to sufficiently describe complex scientific phenomena.
Why was the rule of the leap year changed through the Gregorian calendar reform?
To make the average length of the year more closely approximate to the tropical year
According to Eratosthenes, when the Sun’s rays striking two cities are parallel to one another, why would the two rays not make the same angle with Earth’s surface?
Because of the curvature of Earth
The stellar parallax is caused by _____.
the refraction of the Sun’s rays by Earth’s atmosphere
When viewed from a city on Earth, the full moon is not always blocked by Earth’s shadow because:
the tilt of the Moon’s orbit being relative to the ecliptic plane prevents that from happening.
Dark matter is detected by:
the pull its gravity exerts on stars.
The circumpolar zone is the part of the sky that:
contains the stars that never seem to set.
Calculating the orbits of celestial bodies within the solar system is easier than those outside it because of the _____.
dominant gravitational attraction of the Sun within the solar system
sun sign astrology
It tries to fit everyone into just 12 groups.
Mimi, an astronaut, floats around within her spacecraft that orbits Earth at a close distance. She also sees objects such as a pen and a guitar float past her. Which of the following is likely to be the cause of her ability to float?
She is in free fall in space
Why does the Sun move north and south in the sky as the seasons change on Earth?
Because of the inclination of the ecliptic
Why are most satellites launched into low Earth orbit?
Because this requires the least launch energy
Declination on the celestial sphere is measured from:
the celestial equator toward the north or south.
Why did most of the scholars of Ancient Greece reject the idea of Earth moving around the Sun?
Because they reasoned that Earth’s movement would cause nearby stars to shift their positions in the sky relative to more distant stars
When is the full moon highest in the sky?
At midnight
The Andromeda galaxy, along with the Milky Way Galaxy, is part of a relatively small cluster of more than 50 galaxies referred to as the _____.
Local Group
On continuous observation of a star, it is noted that the wavelengths of the dark lines in its absorption spectrum appear shortened. Which of the following is the most logical conclusion to make here?
The star is approaching Earth.
The space between the stars contains a sparse distribution of gas intermixed with tiny solid particles. These particles are referred to as _____.
interstellar dust
The transitions of electrons of a hydrogen atom to or from the ground state result in the emission or absorption of _____.
ultraviolet photons
Why do astronomers prefer sidereal time for planning their observations?
Because a star always rises at the same sidereal time every day
deductions of Nicolaus Copernicus?
The nearer a planet is to the Sun, the greater its orbital speed.
_____ is simply the local standard time of a place plus 1 hour.
Daylight saving time
Spring tides on Earth are caused by the:
combined tidal effect of the Sun and the Moon.
Quasars?
They are the most distant objects observable in space.
accurately describes the tilt of Earth’s Northern Hemisphere during the equinoxes?
It tilts sideways in relation to the Sun.
Outside the world of science, ultraviolet light is sometimes called “black light” because:
it cannot be seen with the naked eye
A planet’s semimajor axis is equal to _____.
its average distance from the Sun
The apparent shift in the direction of an object as a result of the motion of the observer is called _____.
parallax
The complete removal of an electron from an atom due to the absorption of sufficient energy by that electron is called _____.
ionization
Why is Earth unable to balance the Moon’s differential forces with Earth’s own gravity? Ignore the effects of the Sun.
Because of the rigidity of the solid part of Earth
The place where a planet is closest to the Sun and moves the fastest is called the _____.
perihelion
_____ is an ancient belief system in which the positions of the Moon, Sun, and planets among the stars of the zodiac are thought to hold the key to understanding what one can expect from life.
Astrology
Examining the planets, Galileo found four moons revolving about Jupiter in times ranging from just under 2 days to about 17 days. Which of the following is the significance of this discovery?
It shows that not everything has to revolve around Earth.
ellipse?
Its widest diameter is called its major axis.
The hottest days in the Northern Hemisphere occur somewhat after the summer solstice because:
the weather involves the air and water covering Earth’s surface, and these large reservoirs take time to absorb heat.
idea in Copernicus’s De Revolutionibus?
All the planets move around the sun.
As Earth orbits the Sun, the distance between Earth and the Sun changes. Many people believe that the changes in seasons are the result of this change in distance. Which of the following statements weakens this belief?
Earth is closest to the Sun when the Northern Hemisphere is in the middle of winter.
inertia?
The tendency of objects in motion or at rest to keep doing what they are already doing
Identify a phenomenon that is caused by the large distance between the Sun and Earth.
The light rays from the Sun hitting Earth as nearly parallel lines
interstellar dust?
It is part of the raw material for stars.
was a contribution to astronomy made by Copernicus?
Heliocentric model of the solar system
molecules?
They are the smallest particles into which any matter can be divided while still retaining its chemical properties.
rays coming from an infinitely distant light source?
They would appear to be parallel.
Why are the planets in the solar system observable from Earth?
They reflect the light of the Sun.
_____ are brilliant centers of distant galaxies, glowing with the light of an extraordinarily energetic process.
Quasars
Today, the term constellation refers to _____.
one of the sectors into which the sky is divided
led to the discovery of Neptune?
Discrepancies in the orbit of Uranus
_____ are helium atoms that have lost their electrons and thus are positively charged.
Alpha particles
The change in seasons in Earth is relatively less pronounced near the equator because the region around the equator:
experiences small variations in the amount of sunlight received in a year.
the telescopes used to observe the universe?
The more light a telescope collects, the fainter the objects it can observe.
Why are dark spectral lines produced in an absorption spectrum, even though the light absorbed by electrons is quickly reemitted by them?
Because the atoms reemit light in all directions
the strongest evidence that the Sun is the center of the solar system?
Venus goes through phases like the Moon.
is the escape speed required by spacecraft on interplanetary missions?
11 km/s
is the reason why astronauts are able to jump much higher and farther when they are on the surface of the Moon than when they are on Earth?
A change in their weights
Why would the pre-telescopic observations of Tycho Brahe have been insufficient for Kepler to deduce the elliptical orbits of planets, if Brahe had observed only planets beyond Mars?
Because of the low eccentricity of their orbits
contributes to cause the time difference between the sidereal month and the solar month?
Earth’s motion around the Sun
Why are gamma rays dangerous for living tissues?
They are very energetic.
Each of Earth’s hemispheres increases in temperature during summer because of:
a change in the angle at which sunlight hits that hemisphere.
hypotheses?
A hypothesis is a proposed explanation that must be able to be tested.
The vernal equinox is a point in the sky where the:
ecliptic crosses the celestial equator.
The number 96 million is represented in scientific notation as 9.6 ×107. Here, the exponent is:
7
what would occur if the eccentricity of an ellipse were increased?
The ellipse would become more elongated.
Matthew, an adventurer, looks up at the sky and believes that it is a great hollow dome with him at the center, and all the stars are at an equal distance from him on the surface of the dome. The top of that dome or the point directly above his head is called the _____.
zenith
The _____ is the Sun’s region consisting of sparse gases that extend for millions of miles in all directions from the apparent surface of the Sun.
corona
Greenwich was selected to lie at the Prime Meridian because it:
is located between continental Europe and the United States.
causes the tidal bulges in the oceans?
Flow of water over certain parts of Earth’s surface
Electromagnetic waves are travelling in space. Which of the following statements must be true in this situation?
They are travelling at the speed of light if they are not interacting with matter.
