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When Mercury crosses a line between the Earth and the Sun; and Mercury is closer to the Earth than the sun, we say Mercury is at what?

Greatest Elongation

How did Eratosthenes estimate the size of the Earth in 240 b.c.?

By comparing whether sun light could reach water down in water wells in two cities at different latitudes and by using simple trigonometry.

If Neil Armstrong stayed on the moon for several weeks, he would notice what?

The earth would exhibit phases, but would not rise or set. The sun would rise and set.

If a planet orbits a star in an ellipse, when the planet is at its closest approach to the star we say the planet is at what?


What is the apparent path of the Sun along the celestial sphere called?

the ecliptic

Kepler's second law, which states that as a planet moves around its orbit it sweeps out equal areas in equal times, and as a consequence what?

Planets travel faster when it is nearer to the sun and slower when it is farther from the sun.

It is sun set(6pm) and the moon is on your meridian. What is the phase?


If the star Vega rises tonight at 11:30 pm, at what time does it rise tomorrow?

at 11:26 pm

What did the RAT accomplish for the rovers on mars?

The RAT was a rock abrasion tool that scraped a hole on a martian rock despite the fear that blueberry-like concretions would cause damage.

Which of the following statements the ecliptic plane is not true?

It is the plane of them moon's orbit around the earth.

Orion is visible on winter evening but not summer evenings because of what?

The location of earth in its orbit.

What happened shortly after the rover spirit landed on gusev crater?

A computer problem with the flash memory completely stopped it from functioning and tense times ensued until scientists at NASA figured it out.

Who was a great observer that charted accurate positions of the planets and later turned over his observations to Kepler?

Tycho Brahe

In order to point our telescope at the star Betelgeuse we need to know its

Right ascension and Declination

How many months of the year is the sun above the celestial equator?


What conclusions are require for a solar eclipse?

The phase of the moon must be new, and the nodes of the moons orbit must be nearly aligned with the earth and the sun.

If the moon is relatively far from the earth, so that the umbra does NOT reach earth, someone directly behind the umbra will see

an annular eclipse

What is the approximate declination of Polaris?

+90 degrees

The amount of time between successive passes of the star Sirius (or any star that is not our sun) across your meridian is what?

23 hr 56 mins (a sidereal day)

Retrograde motion is when

A planet appears to move westward against the background stars

What is not a consequence of the precession of the Earth's spin axis?

The plane of the ecliptic cuts through the constellations of the zodiac on the celestial sphere.

Galileo and Kepler had in common that they

both supported the Heliocentric model of the cosmos--however they arrived at this conclusion for very different reasons.

Earth is made mostly of metals and rocks. Where did the heavy elements that make up these materials come from?

They were produced by nuclear fusion events when stars supernova. These stars predated our solar system.

The time period between successive occurrences of the spring equinox is what?

A tropical year.

Aristotle's idea of the cosmos was...?

Geocentric with celestial bodies made up of a light substance called quintessence floating above a heavy earth.

Which Greek philosopher was credited as being the first to propose a model of the universe that did not rely on supernatural forces?


He discovered Jupiter has moons because he was first to use a telescope


About where is the sun (and our solar system) located withing the Milky Way galaxy?

A little over half way from the galactic center to the edge of the galactic disk.

Who was the first person to teach that the earth itself was a sphere?


Who proposed the first recorded heliocentric model of the cosmos?


What is the tropic of cancer?

It is a place where the sun is directly overhead at noon on the summer solstice.

Before When we look at the andromeda galaxy tonight through our telescope, we see this galaxy as what?

as it was 2.5 million years ago when the light we are seeing today left that galaxy

When someone on the earth observes the moon in the first-quarter phase, someone on the moon facing the earth observes the earth in the

Third-quarter earth phase.

If mars is on your meridian and it is midnight, we say that mars is at


On the day of the Vernal Equinox the spin axis of the earth and a line drawn between the earth and the sun

Are perpendicular

Why do we have seasons on Earth?

The spin axis of the earth is tilted 23.5 degrees

Keplers third law states


Your local sidereal time is 4 hours and 55 minutes. Which of the following objects would be easiest to view for you at this time?

A star that has a right ascension 5 hours 10 minutes and declination 30 degrees.

When an electron in a hydrogen atom jumps from the higher second excited state down to the first excited state we observer that the atom

Emits a photon with wavelength 656 nm

Which planets have a ring system?

Jupiter, Neptune, Uranus, and Saturn

How often do high tides occur?

Every 12 hours 25 minutes

If a scientist studies the wavelengths of photons give off by a hoe gas of a particular element, he/she will be able to determine what?

The identity of the element

Two stars are identical in size but star A is twice the temperature (in kelvin) as star B. Since the stars are thermal emitters we know that in any given time period that what?

Star A emits 16 times as much energy as Star B emits.

According to the universal law of gravitation, if you triple the distance between two object, then the gravitational force between them will

decrease by a factor of 3

How did Newton correct Kepler's first law?

Newton said that the star and planet orbit their common center of mass and that the orbit may not be an ellipse--it may be unbounded.

How would you calculate the frequency of red light traveling in free space if you know its wavelength.

Divide the wavelength by the speed of light.

Saturn is the least dense of all planets


How can astronomers tell the temperature of a star or planetary surface?

From the thermal emission spectrum of the star or planetary surface and Wien's Law.

The thermal emission spectrum from a dense object depends only upon what?

the objects temperature.

The thermal emission spectrum of the blueish star Sirius peaks at 400 nm, and the thermal emission spectrum of the reddish stat Betelgeuse peaks at 700 nm. Wien's Law tells us that

Betelgeuse is cooler than Sirius.

X rays and gamma rays cannot be studies with telescopes on the ground.


The moon is moving farther away from the Earth at a rate of 3.8 centimeters a year.


A distant star has spectral lines that are red-shifted. What can you say about that star?

The star is traveling away from us.

Why does the moon always show the same face toward Earth?

It is already tidally locked to the earth.

The energy of a photon is

E=h f

Diffraction is what?

The bending of light rays as they pass through a small opening in an opaque object.

We can best understand the basic structure of an atom as

a nucleus about which electrons occupy energy levels that are determined by the wave nature of the electron as understood by quantum mechanics.

Who was the first person to be able to describe the trajectory of the moon?


What are the two most important properties of a telescope as far as determining the quality of the image?

Light gathering ability and resolution.

Can corrective optics completely fix or eliminate resolutions problems due to diffraction?

No this limit of angular resolution is due to the nature of light and no correction is possible.

Compare the limit of angular resolution due to diffraction of a 3 meter optical telescope to a 3 meter radio telescope. Which one will have the sharper image?

The optical telescope because it operates at shorter wavelengths

What type of spectrum is emitted from a hot gas?

An emission line spectrum

The mass of jupiter can be calculated by

measuring the orbital period and semi major axis of one of Jupiters moons

You wish to determine the rate of rotation of a planet. The surface features of the planet are difficult to see so you choose an alternate method. What was this method?

You bounce a radio wave off of the planet to look at the broadening of the echo and use the doppler effect to calculate the velocity.

The rate at which the earth is spinning on its axis is gradually slowing down because of what?

Tidal friction

A planet that has a low density compared mostly of hydrogen and helium, with many moons and a ring system is classified as a

jovian planet

What color is 700 nm light?


What does E=mc^2 mean?

The amount of energy released in an amount of mass m were to be converted directly into energy.

How can an astronomer determine how rapidly a star is spinning on its axis?

By determining if any spectral lines are broadened.

The longer the wavelength of a photon

the lower the frequency

What is interferometry used for and why?

It is used by radio astronomers to reduce the and angular resolution as limited by diffraction by using the signals of several radio telescopes

The higher the frequency of a photon

the higher the energy

What does temperature measure on a microscopic level?

The average kinetic energy of particles in a substance.

Light from the sun passes through a cool planetary atmosphere. What type of spectrum results?

an absorption line spectrum

The fact that Venus has been spinning on its axis for more than 4 billion years and will continue spinning on its axis for billions of more years as long as no torque acts upon it is a statement of

conservation of angular momentum.

What is the frequency of light traveling through free space that has a wavelength of 2 meters?

1.5x10^8 Hz

The cloud surface of Jupiter and Saturn appears stripped latitudinally with brown belts and white zones. What is this?

Zones and belts are the result of convection cells that have easterly and westerly zonal winds due to the coriolis effect on the planets.

Why does earth not have a thick layer of hydrogen and helium about it like Jupiter does?

Because Jupiter formed where the temperatures are cooler so that hydrogen and helium could be gravitational bound to the larger planetary seeds

Where do the particles in the plasma torus that surrounds Jupiter originate from?

Volcanoes on the moon Io

Earths magnetic field has

Switched polarity 9 times in the last 3.5 million years

How did Earth break out of its Ice Age?

The carbon dioxide cycle as as perciptation decreased due to ice sheets allowing CO2 to build up.

The Cassini spacecraft recently made an interesting discovery about the moon Enceladus, What was it?

Geological activity in the form of jets of water ice or steam from the surface of the south pole.

What is the stratosphere?

The part of the atmosphere that absorbs the ultraviolet by ozone

The moon Tritan

Will some day break up into pieces as it gets too close to Neptune and its pieces will orbit Neptune most likely making a ring system.

A key requirement for differentiation to occur on a planet is what?

Enough heat so that at some point the planet is completely or at least mostly melted,

Planets ultimately cool by giving off radiation which is explained by thermal emission.


How long does one day on Jupiter last?

Jupiter does not rotate on its axis

In the solar nebula, what mainly determines if a planet turns out to be a terrestrial or a jovian planet?

The temperature and conditions of the solar nebula.

The only way to see any of the surface of this terrestrial planet is to use radar to penetrate the thick clouds. What planet is this?


What clues do we have about what triggered the collapse of the solar nebula to form our solar system?

radioactive isotopes found in meteorites suggest that our solar system was triggered by a nearby supernova.

The last 1 million years has been a time of intense climatic change harboring a dozen or so ice ages. Why?

Milankovitch theory suggests these are due to changes in the tilt of the Earth's spin axis and eccentricity of orbit.

An interesting fact about Europa, a moon of Jupiter, is what?

There could be an ocean underneath the icy surface of this moon.

What are greenhouse gases?

Gasses that absorb infrared light from the ground

Sunsets are red because

atmospheric gases scatter blue light more than red that by the time the sunlight reached you at sunset, mostly red is what is left.

How does the nebular theory account for exceptions to the patterns of motion that we see in our solar system?

These exceptions were most likely caused by giant impacts

Which moon in our solar system has an atmosphere too thick to see through from orbit, dry riverbeds, and a space probe has landed on it?


Io is only slightly larger than Earth's moon and yet it is still volcanically active and Earth's moon is not. Why?

Tidal flexing and tidal heating supply heat that powers the volcanic activity.

The Maria formed on the moon after several large impacts made huge craters and runny lava filled these basins


Why is Neptune blue

Because Neptune has some methane gas in its atmosphere which absorbs red light leaving blue.

Why is Venus hotter than Mercury even though it is farther away from the sun?

Venus has a thick carbon dioxide atmosphere.

Where is the frostline in the formation of our solar system?

Between the orbits of Mars and Jupiter

How old is our solar system?

About 4.6 billion years old

Venus received about as much H2O as Earth. Where is the water on Venus today?

Heat caused any liquid water present to to turn into vapor and then UV photo dissociation of H2O vapor allows H to thermally escape.

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