Midterm 1 Flashcards
what is the address of you?
you, Earth, solar system, Milky Way, Local Group, Local Supercluster
About where is our solar system located within the Milky Way Galaxy?
about two-thirds of the way from the center of the galaxy to the outskirts of the galactic disk
What do we mean when we say that the universe is expanding?
Average distances are increasing between galaxies
Earth is made mostly of metals and rocks. Where did this material come from?
It was produced by nuclear fusion in stars.
Suppose we look at a photograph of many galaxies. Assuming that all galaxies formed at about the same time, which galaxy in the
picture is the youngest?
the one that is farthest away
Which of the following is largest? A) size of Pluto's orbit B) 1 light-year C) distance to the nearest star (other than our Sun) D) size of a typical galaxy
D) size of a typical galaxy
What is an astronomical unit?
the average distance from Earth to the Sun
Patterns of stars in constellations hardly change in appearance over times of even a few thousand years. Why?
The stars in our sky actually move rapidly relative to us—thousands of kilometers per hour—but are so far away that it
takes a long time for this motion to make a noticeable change in the patterns in the sky.
What do we mean by the observable universe?
the part of the universe that could be observed in principle, including things that may require future technologies
Which of the following is smallest? A) 1 AU B) 1 light-second C) size of a typical star D) size of a typical planet
D) size of a typical planet
Which of the following best describes the modern definition of a constellation?
A) a collection of stars that are near one another in space
B) a region of the celestial sphere
C) a Greek mythological figure
D) a group of stars that all lie at about the same distance from Earth
E) a pattern of bright stars in the sky
B) a region of the celestial sphere
Which of the following statements about the celestial sphere is not true?
A) The “celestial sphere” is just another name for our universe.
B) The celestial sphere does not exist physically.
C) Earth is placed at the center of the celestial sphere.
D) When we look in the sky, the stars all appear to be located on the celestial sphere.
E) From any location on Earth, we can see only half the celestial sphere at any one time.
B) The celestial sphere does not exist physically.
What is the ecliptic?
the Sun’s apparent path along the celestial sphere
How do you best describes the meridian in your sky?
a half-circle extending from your horizon due north, through your zenith, to your horizon due south
Which of the following statements does not use the term angular size or angular distance correctly?
A) The angular size of the Sun is about the same as that of the Moon.
B) The angular distance between those two houses in the distance is 30°.
C) You can use your outstretched hand to estimate angular sizes and angular distances.
D) The angular size of the Moon is about 1/2 degree.
E) The angular distance between those two bright stars in the sky is about 2 meters.
E) The angular distance between those two bright stars in the sky is about 2 meters.
What is a circumpolar star?
a star that always remains above your horizon
You are standing on Earth’s equator. Which way is Polaris, the North star?
on the northern horizon
By locating the north celestial pole (NCP) in the sky, how can you determine your latitude?
The altitude of the NCP is the same as your latitude.
Why do we have seasons on Earth?
As Earth goes around the Sun and Earth’s axis remains pointed toward Polaris, the Northern and Southern hemispheres
alternately receive more and less direct sunlight
Which of the following statements about lunar phases is true?
A) The time between new Moons is two weeks.
B) It is possible to have two full Moons during November, but not during December.
C) It is possible to have two full Moons during January, but not during February.
D) The full Moon sometimes rises around midnight.
E) The time from one new Moon to the next new Moon is the same as the time from first-quarter Moon to third-quarter
Moon.
B) It is possible to have two full Moons during November, but not during December.
When someone on Earth observes the Moon in the first-quarter phase, someone on the Moon facing Earth observes Earth in the
E) third-quarter Earth phase.
If the Moon is rising at midnight, the phase of the Moon must be
third quarter.
Why do we see essentially the same face of the Moon at all times?
C) because the Moon’s rotational and orbital periods are equal
All of the following statements are true. Which one explains the reason why there is not a solar eclipse at every new Moon?
A) The Moon rotates synchronously with its revolution about Earth.
B) The nodes of the Moon’s orbit precess with an 18-year period.
C) The Moon is the primary cause of tides on Earth.
D) The orbital plane of the Moon is tilted by about 5° to the ecliptic plane.
E) The sidereal month is shorter than the lunar month.
E) The sidereal month is shorter than the lunar month.
What conditions are required for a solar eclipse?
The phase of the Moon must be new, and the nodes of the Moon’s orbit must be nearly aligned with Earth and the Sun.
What causes the apparent retrograde motion of the planets?
As Earth passes another planet, the other planet appears to move backward with respect to the background stars, but the
planet’s motion does not really change.
We can’t detect stellar parallax with naked-eye observations. Which of the following would make parallax easier to observe?
A) slowing down Earth’s rotational motion
B) getting away from streetlights
C) speeding up the precession of Earth’s axis
D) speeding up Earth’s rotational motion
E) increasing the size of Earth’s orbit
E) increasing the size of Earth’s orbit
The lunar month is longer than the sidereal month because
the Moon has to complete more than one full orbit around Earth to complete the cycle of lunar phases
Which of the following is the reason for the leap years?
A) the non-circular orbit of Earth around the Sun
B) precession of Earth’s axis
C) the combined effect of the rotation of Earth and its orbit about the Sun
D) Earth year being a non-integer number of Earth days
E) the tilt of Earth’s axis
D) Earth year being a non-integer number of Earth days
The south celestial pole appears on your meridian at an altitude of 30° in the south. Where are you?
latitude = 30°S
Suppose you live at latitude 40°N. How can you describes the path of the celestial equator through your sky?
It goes from due east on your horizon, to an altitude of 50° in the south, to due west on your horizon.
Suppose you live at latitude 40°N. How can you describe the conditions that make a star circumpolar?
Stars are circumpolar if they have declination > +50°.
Suppose the date is June 21 and the Sun never sets, just touching your northern horizon at midnight. Where are you?
the Arctic Circle
The Sun is on your meridian, and you have a UT clock that tells you it is 3 P.M. in Greenwich. What is your longitude?
45° west of Greenwich
How did the Ptolemaic model explain the apparent retrograde motion of the planets?
It held that the planets moved along small circles that moved on larger circles around Earth.
When Copernicus first created his Sun-centered model of the universe, it did not lead to substantially better predictions of
planetary positions than the Ptolemaic model. Why not?
Copernicus used perfect circles for the orbits of the planets.
Who discovered that the orbits of planets are ellipses
Kepler
From Kepler’s third law, an asteroid with an orbital period of 8 years lies at an average distance from the Sun equal to
4 astronomical units.
Kepler’s second law, which states that as a planet moves around its orbit it sweeps out equal areas in equal times, means that
a planet travels faster when it is nearer to the Sun and slower when it is farther from the Sun.
What is meant by a hypothesis?
an explanation for a phenomenon that makes a prediction
Which of the following statements about scientific theories is not true?
A) A theory can never be proved beyond all doubt; we can only hope to collect more and more evidence that might support it.
B) A theory cannot be taken seriously by scientists if it contradicts other theories developed by scientists over the past several
hundred years.
C) A theory is a model designed to explain a number of observed facts.
D) If even a single new fact is discovered that contradicts what we expect according to a particular theory, then the theory
must be revised or discarded.
E) A theory must make predictions that can be checked by observation or experiment.
B) A theory cannot be taken seriously by scientists if it contradicts other theories developed by scientists over the past several
