Q&A Hero

Q: In Ptolemy's geocentric model, the planet's motion along its deferent is all that is needed to understand retrograde motion.

Q: According to Copernicus, retrograde motion occurs at opposition for the outer planets.

Q: Galileo's observations of the entire phase cycle of Venus proved that Ptolemy's epicycles could not be correct in keeping Venus between us and the Sun.

Q: Among Galileo's discoveries with his telescope were sunspots.

Q: Kepler's third law relates the square of the planet's orbital period in years to the cube of its average distance from the Sun in astronomical units.

Q: Kepler relied heavily on the telescopic observations of Galileo in developing his laws of planetary motion.

Q: Kepler found the orbits of planets are ellipses, not circles.

Q: A planet (or comet) will speed up as it approaches the Sun.

Q: According to Kepler's third law, if you know the planet's orbital period, you can find its average distance from the Sun.

Q: Kepler's third law allows us to find the average distance to a planet from observing its period of rotation on its axis.

Q: According to Newton's first law, an object traveling in a circle does not have a force acting on it.

Q: According to Newton's second law, if you double the force acting on a body, the acceleration will double.

Q: Compared to when it was on the surface, a satellite in an orbit whose radius is about 4 times the Earth's radius will experience about 1/16 the force due to the Earth's gravity.

Q: According to Newton's third law, when the Voyager probes passed Jupiter in 1979, they exerted exactly the same force on Jupiter as the giant planet did on them.

Q: We get a new and full moon every month. Why don't we get two eclipses every month?

Q: Which is longer, the sidereal or synodic month? Why?

Q: Describe how Eratosthenes measured the circumference of our planet.

Q: What is the astronomical significance of 26,000 years?

Q: What conditions are necessary for a total solar eclipse?

Q: Why can many more people witness a total lunar eclipse than a total solar eclipse?

Q: Contrast the sidereal and solar days.

Q: The Sun and stars rise in the east, and set in the west. Contrast ancient and modern explanations for this observation.

Q: Compare hours of right ascension to time zones on the Earth.

Q: Compare and contrast longitude and right ascension.

Q: Compare and contrast latitude and declination. How does each relate to your position on Earth?

Q: If Sirius transits my local meridian tonight at 6:43 PM, when will it transit tomorrow?

Q: Why is Polaris not always the pole star, and when does it get another chance?

Q: If the Moon rises exactly at sunset, what will its phase be? Why?

Q: The last quarter moon rises tonight about midnight; when will it rise, and what will its phase be tomorrow night?

Q: The first quarter moon rises about noon today; what will its phase be, and when will it rise tomorrow?

Q: How far above and below the celestial equator can the Sun move?

Q: How long does the synodic month take, and how it this observed?

Q: What is the length of the sidereal month, and how is it determined?

Q: Why are some solar eclipses total, and others annular?

Q: What happens on or about March 20th, and what does the name signify?

Q: How far above or below the equator can the Sun appear to move? Why?

Q: Pensacola, Florida lies at a latitude of 30 degrees north. Where is Polaris in its sky?

Q: Which star shows the least motion in the northern sky over the course of an hour?

Q: If intending to teach his students the constellations by season, why would an astronomy instructor be advised to always assign the stars in the current western sky at the beginning of each term?

Q: How far above or below the ecliptic can the Sun move?

Q: At the solstice, what is the maximum angle the Sun can be above or below the equator?

Q: Which is longer, the sidereal or solar day? By how much?

Q: What are the minimum and maximum values for right ascension in the sky?

Q: Define the celestial sphere.

Q: How are right ascension in the sky and longitude on Earth different?

Q: What are the minimum and maximum values for declination in the sky for both north and south?

Q: How is right ascension similar to longitude on Earth?

Q: What do both latitude on Earth and declination in the sky measure?

Q: One of the requirements of the Scientific Method is that an experiment must be ________.

Q: If two observatories on opposite sides of the Earth were to measure the position of a star to calculate its parallax, then the diameter of the Earth would be the ________.

Q: If one star has a parallax ten times larger than another's, the first star is ________.

Q: Sirius has a parallax of 0.38", while Alpha Centauri's is 0.77." Alpha Centauri is about ________ as Sirius.

Q: The apparent angular shift of any object across a distant background, when viewed from two different places, is called ________ shift.

Q: That we do not get eclipses every new and full Moon is due to the ________ degree tilt of the Moon's orbit, relative to the ecliptic.

Q: Over the course of the year, the Sun's noon altitude varies by ________ degrees.

Q: Our seasons are a consequence of the Earth's 23.5 degree ________.

Q: If the Moon is on the ecliptic, new, and at its farthest distance from Earth, we will get a(n) ________ solar eclipse.

Q: If the Moon rises at sunset, then its phase must be ________.

Q: The apparent annual path the Sun takes through the sky is called the ________.

Q: The time for the Moon to orbit the Earth, relative to the distant stars is the ________.

Q: The time interval of 365.242 days is defined as the ________.

Q: The twelve constellations through which the Sun passes are signs of the ________.

Q: Like latitude on Earth, ________ in the sky is measured in degrees north and south of the equator.

Q: In general, what is true of the alpha star in a constellation? A) It is the brightest star in the constellation. B) It is the easternmost star in the constellation. C) It is the westernmost star in the constellation. D) It is the reddest star in the constellation. E) It is the star that is closest to Earth.

Q: Into how many constellations is the celestial sphere divided? A) 12 B) 44 C) 57 D) 88 E) 110

Q: A star with a declination of +60.0 degrees will be A) east of the vernal equinox. B) west of the vernal equinox. C) north of the celestial equator. D) south of the celestial equator. E) None of these answers are correct.

Q: What are constellations? A) Groups of galaxies gravitationally bound and close together in the sky. B) Groups of stars making an apparent pattern in the celestial sphere. C) Groups of stars gravitationally bound and appearing close together in the sky. D) Ancient story boards, useless to modern astronomers. E) Apparent groupings of stars and planets visible on a given evening.

Q: A star with a right ascension of 1.0 hours will rise A) 1.0 hours before the vernal equinox. B) 13.0 hours before the vernal equinox. C) 1.0 hours after the vernal equinox. D) 11.0 hours after the vernal equinox. E) at the same time as the vernal equinox.

Q: The twelve constellations the solar system bodies move through are the A) equatorial constellations. B) signs of the zodiac. C) nodes of the ecliptic. D) galactic equator. E) stages of heaven.

Q: The 26,000 year cycle that changes the poles and equinoxes is called A) a retrograde loop. B) the Earth's rotation. C) precession. D) regression. E) revolution.

Q: This diagram explains A) the difference between solar time and sidereal time. B) precession. C) the solar day's relation to the Moon. D) the sidereal day's relation to the seasons. E) the reason for the solstices.

Q: From the horizon to the observer's zenith is an angle of A) 30 degrees for observers at a latitude of 30 degrees North. B) 90 degrees for everyone on the Earth. C) 23.5 degrees for observers at the Tropics of Cancer and Capricorn. D) 66.5 degrees for everyone on the Earth. E) 0.0 degrees for an observer at the Earth's north pole.

Q: That Polaris will not always be the pole star is due to A) the sidereal day being shorter than the solar day. B) precession shifting the celestial pole. C) the Moon following the ecliptic, instead of the equator. D) the Earth's revolution being slightly less than exactly 365.25 days. E) the Solar winds blowing the Earth farther away from the Sun.

Q: As you watch a star, you see it move 15 degrees across the sky. How long have you been watching it? A) 1 hour B) 3 hours C) 15 minutes D) 15 seconds E) 1 minute

Q: You note that a particular star is directly overhead. It will be directly overhead again in A) 1 hour. B) 12 hours. C) 23 hours 56 minutes. D) 24 hours. E) 24 hours 4 minutes.

Q: When the Moon is directly opposite the Sun in the sky, its phase is A) new. B) waxing or waning crescent. C) first or third quarter. D) waxing or waning gibbous. E) full.

Q: The fact that the Earth has moved along its orbit in the time it took to rotate once is the reason for A) the difference between solar and sidereal time. B) precession. C) seasons. D) the position of the Celestial Equator. E) Earth's 23.5-degree tilt.

Q: If Taurus is now rising at sunset, which constellation will rise at sunset next month? A) Scorpius B) Aquarius C) Gemini D) Aries E) Pisces

Q: If Scorpius is now prominent in the summer sky, in 13,000 years it will be best seen A) at the same season; the heavens do not change. B) in the autumn. C) in the winter sky. D) in the spring sky. E) It will not be visible then at all. All of its stars will have vanished by then.

Q: The star Thuban in Draco A) lies as the center of the precession cycle. B) was an excellent north pole star in 3,000 BC. C) is brighter than Polaris. D) lies halfway between the bowls of the Big and Little Dippers. E) is used to locate the vernal equinox.