Astronomy – Space Terms

Flashcard maker : Maddison Bailey
Two stars that are in the same constellation:
may actually be very far away from each other.
Beijing and Philadelphia have about the same latitude but very different longitudes. Therefore, tonight’s night sky in these two places
will look about the same
In winter, Earth’s axis points toward the star Polaris. In spring
the axis also points toward Polaris
When it is summer in Australia, it is:
winter in the United States.
If the Sun rises precisely due east:
it must be the day of either the spring or fall equinox
A week after full moon, the Moon’s phase is:
third quarter
Some type of lunar or solar eclipse (not necessarily a total eclipse) occurs
at least four times a year
If there is going to be a total lunar eclipse tonight, then you know that:
the Moon’s phase is full.
When we see Saturn going through a period of apparent retrograde motion, it means:
Earth is passing Saturn in its orbit, with both planets on the same side of the Sun
Which of the following was not a major advantage of Copernicus’s Sun-centered model over the Ptolemaic model?
It made significantly better predictions of planetary positions in our sky.
When we say that a planet has a highly eccentric orbit, we mean that:
in some parts of its orbit it is much closer to the Sun than in other parts
Earth is closer to the Sun in January than in July. Therefore, in accord with Kepler’s second law:
Earth travels faster in its orbit around the Sun in January than in July
According to Kepler’s third law:
Jupiter orbits the Sun at a faster speed than Saturn.
Tycho Brahe’s contribution to astronomy included:
collecting data that enabled Kepler to discover the laws of planetary motion.
Galileo’s contribution to astronomy included:
making observations and conducting experiments that dispelled scientific objections to the Sun-centered model.
Which of the following is not true about scientific progress?
Science advances only through the scientific method.
Which of the following is not true about a scientific theory?
A theory is essentially an educated guess.
Tell how you can find the ecliptic in the sky. Tell how you can find the zodiac.
The ecliptic can be traced roughly by the positions of the moon and planets visible in the night sky. Note the sunset point on the western horizon, then trace out an arc through the visible planets and moon. Those constellations lying along this arc are the signs of the zodiac; many of them are bright enough to be easily identified by their star patterns, such as Scorpius, Sagittarius, Taurus, Gemini, and Leo. The ecliptic passes through all twelve zodiacal constellations.
For what two reasons did ancient astronomers believe (correctly) the moon to be closer to the earth than the sun is?
The moon moves faster in the sky than the sun (twelve degrees per day, as opposed to one degree per day for the sun); as a rule, closer objects move more notably. At a solar eclipse, it is obviously the dark moon passing between us and the more distant brilliant sun.
Describe the changing position of the rising sun on the eastern horizon throughout the year, with special emphasis on the solstices and equinoxes.
At equinoxes, the sun rises due east, and sets due west. At the Vernal Equinox (March 21) the sun rises farther north each morning, reaching its northernmost point at summer solstice about June 21. It then turns back south, and is farthest south on December 21 at winter solstice.
What phase must the moon be in for a solar eclipse to occur? A lunar eclipse?
Solar eclipses require a new (dark) moon between us and the sun. Lunar eclipses happen when the full moon moves into the shadow cast by the earth.
sidereal time (star time)
at a particular location is equal to Right Ascension, RA, value of the stars that are directly overhead. The amount of time elapsed at a point is simply the difference in RA values between the stars directly overhead now and those that were overhead at the start.

A sidereal day is the time from day to day until the same stars are directly overhead. Because the earth is traveling around the sun and also rotating on its axis, a sidereal day comes out to 23 hours 56 minutes which is 4 minutes short of the solar day.

solar day
the time for the sun to repeat its position in the sky, 24 hours. A solar year is 365 _ solar days long. Leap year is important, in which we add an extra day every 4th year, since it acts to keep the first day of Winter, for example, within a day or two of December 21st over long periods of time.
How did Aristotle’s model explain the apparent lack of motion by the earth?
Natural motion of earthly material is to fall toward the center of the universe. Once there, it has no natural motion.
How did Aristotle’s model explain the daily motion of the stars?
The natural motion of the celestial sphere is to rotate. The sphere of the fixed stars did so daily from east to west.
How did Aristotle’s model explain the annual motion of the sun through the zodiac?
The sun’s motion was again the natural motion of the celestial body’s sphere yearly from west to east. Evidence that the sun moved and not the earth was lack of an annual parallax of the stars.
How did Aristotle argue against a heliocentric model?
The spherical shape of the earth assumed a spherical geometry dominated the entire universe, aesthetically a pleasing conclusion. Physically, the earth is made of material whose natural motion was toward the center of the cosmos. Also, the lack of an annual stellar parallax implied that the earth did not move around the sun. Note that parallax here is NOT the same as the modern stellar parallax used to measure the distance to the closer stars.
In the Ptolemaic model, how did observations set the period of the epicycle? The deferent?
According to Ptolemy, epicycles produce retrograde motions. Thus the time between the beginning of the retrograde motions, essentially the synodic period, must be the epicycle’s period. The motion along the deferent produces the normal west to east (eastward) motion of the planet along the ecliptic. So the period of the deferent is the length of time it takes the planet to circuit the zodiac once (twelve years, in the case of Jupiter).
State one strength of Ptolemy’s model.
It was in harmony with the physics of the day, especially the concepts of natural and forced motion.
How does a geocentric model differ from a heliocentric one in its prediction of an annual stellar prallax?
In the geocentric model, NO annual stellar parallax occurs.
What is the crucial observational test for a heliocentric model?
A heliocentric model predicts that annual stellar parallax should occur.
Suppose you visit another planet:
Your mass would be the same as on Earth, but your weight would be different.
Consider the statement “There’s no gravity in space.” This statement is:
Completely false.
If you want to make a rocket turn left, you need to:
Fire an engine that shoots out gas to the right
Earth’s angular momentum when it is at perihelion (nearest to the Sun) in its orbit is:
Exactly the same as its angular momentum at aphelion
As an interstellar gas cloud shrinks in size, its gravitational potential energy:
gradually is transformed into other forms of energy
If Earth were twice as far from the Sun, the force of gravity attracting Earth to the Sun would be:
one-quarter as strong
According to the law of universal gravitation, what would happen to Earth if the Sun were somehow replaced by a black hole of the same mass?
Earth’s orbit would not chang
If the Moon were closer to Earth, high tides would:
be higher than they are now.
Why is a sunflower yellow?
It reflects yellow light.
Blue light has higher frequency than red light. Thus, blue light has:
higher energy and shorter wavelength than red light.
Compared to an atom as a whole, an atomic nucleus:
s very tiny but has most of the mass.
Some nitrogen atoms have seven neutrons and some have eight neutrons. These two forms of nitrogen are:
isotopes of each other.
The set of spectral lines that we see in a star’s spectrum depends on the star’s:
chemical composition.
A star whose spectrum peaks in the infrared is:
cooler than our Sun.
A spectral line that appears at a wavelength of 321 in the laboratory appears at a wavelength of 328 in the spectrum of a distant object. We say that the object’s spectrum is:
How much greater is the light-collecting area of a 6- telescope than a 3- telescope?
four times
The Hubble Space Telescope obtains higher-resolution images than most ground-based telescopes because it is:
above Earth’s atmosphere.
How did the Ptolemaic model explain the apparent retrograde motion of the planets?
t held that the planets moved along small circles that moved on larger circles around the earth.
Why did Ptolemy have the planets orbiting the earth on “circles upon circles” in his model of the universe?
to explain the fact that planets sometimes appear to move westward, rather than eastward, relative to the stars in our sky
Where was the Sun in Ptolemy’s model of the universe?
between the orbits of Venus and Mars
During the Dark Ages in Europe, the scientific work of the ancient Greeks was preserved and further developed primarily by scholars in
Which of these groups of particles has the greatest mass?
four individual protons
Scientists estimate the central temperature of the Sun using
mathematical models of the Sun.
Why do sunspots appear darker than their surroundings?
They are cooler than their surroundings.
At the center of the Sun, fusion converts hydrogen into
helium, energy, and neutrinos.
Solar energy leaves the core of the Sun in the form of
How does the number of neutrinos passing through your body at night compare with the number passing through your body during the day?
about the same
Which of these things poses the greatest hazard to communications satellites?
protons from the Sun

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