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Hw 1-12

How long does it take light to travel a distance of one light year?

One year or about pi x 107 seconds.

• What is the unit that we use to measure distances in the solar system?

The astronomical unit or AU is very convenient.

• If Earth rotated on its axis twice as fast as it currently does, but its motion around the Sun stayed the same, then

the night would be half as long

• A long thin cloud that stretched from directly overhead to the western horizon would have an angular size of

90 degrees

6. In December we would see the Sun in the direction of the constellation(s)...

Sagittarius and Capricorn

If the Moon's orbit around Earth were a little larger, solar eclipses would be

more likely to be annular

What two pieces of information are needed to determine the diameter of a far away object?

Distance and angular size

The seasons are caused by the precession of the Earth's


The solar day is longer than the sidereal day


The most northern location on Earth where the Sun can be seen directly overhead at noon is called

The Tropic of Cancer

What is the approximate position of Polaris on the Celestial Sphere?

Approximately RA = 2h 30 min, Dec = 89 degrees

The Age of Aquarius refers to what?

It means that in the future the vernal equinox will occur in a direction in line with the constellation Aquarius due to the precession of the Earth's axis of rotation.

5. When a thin crescent of the Moon is visible just before sunrise, the Moon is in its

waning phase

you put an apple 10 m away from your eye in line with the moon, what do you predict?

It would "eclipse" the moon.

• The alpha star in a constellation is (as seen from Earth):

The brightest star in a constellation as seen from Earth.

• A major flaw in Copernicus's model was that it still had

Circular Orbits

• An asteroid with an orbit lying entirely inside Earth's orbit

has an orbital semimajor axis of less than 1 AU

• Galileo's observations of Venus demonstrated that Venus must be

Orbiting the Sun

• showing the motion of a ball near Earth's surface, depicts how gravity

Causes the ball to accelerate downwards

• How long would a radar signal take to complete a round trip between Earth and Mars when the two planets are 0.7 AU apart?

about 11.6 minutes

• The light coming from a star has a dominant wavelength of 1000 nm. How hot is the star in degrees Kelvin?


• What is the dominant wavelength in nanometers of the light coming from a very hot star (about 29,000 K)?


• The H-alpha spectral line 656 nm coming from a distant star appears at a wavelength of 100 nm in the spectrometer. What can we say about the star?

It is moving towards us at 85% the velocity of light

• Comet X orbits the Sun every 10 years. What is the average distance (semi major axis) of the comet from the sun?

4.64 AU

• The temperature of a distant star is determined to be 59,000 K. How much more power does it emit than the sun does?

10,000 times more

• The main advantage to using the Hubble Space Telescope it that focusing problems due to atmospheric disturbances are eliminated


• The term "seeing" is used to describe how bright an object the human eye can tolerate without damage to the retina.


• A CCD is used to electronically record images from a telescope


• Radio telescopes are large in part to improve their angular resolution, which is poor because of the long wavelengths at which they


• Infrared astronomy can only be done from space


• X-ray and gamma-ray telescopes employ the same basic design as optical instruments


• Because gamma rays have very short wavelengths, gamma-ray telescopes can achieve extremely high angular resolution


• The main reason that most professional research telescopes are reflectors is that

mirrors produce sharper images than lenses do since there is no chromatic aberration.their images are inverted

• If telescope mirrors were made in odd sizes, the one with the most light-gathering power (even if the mirror is not circular) would be

a rectangle with two 1-m sides and two 2-m sides.

The PRIMARY reason professional observatories are built on the highest mountain tops is to

Reduce atmospheric blurring

When multiple radio telescopes are used for interferometry, resolving power (angular resolution) is most improved by increasing

the distance between telescopes

The Spitzer Space Telescope is stationed far from Earth because

This infrared telescope actually does not orbit the Earth, but follows our planet around the Sun, reducing the heat interference from Earth

The best way to study young stars hidden behind interstellar dust clouds would be to use

Infrared light

(Resolution) is sharpest when the ratio of wavelength to telescope size (i.e. lambda/D)

is small

the best frequency range in which to study the hot (million-kelvin) gas found among the galaxies in the Virgo cluster would be

in x-rays

An FSU student is observing the phases of Venus with his 8 inch reflector telescope, and a UF student is doing the same with a 16 inch reflector telescope. How much more light gathering power does the UF telescope have?

4 times more

Again, an FSU student is observing the phases of Venus with his 8 inch reflector telescope, and a UF student is doing the same with a 16 inch reflector telescope. How much "more" resolving power (i.e. angular resolution) does the UF telescope have?

Twice as much.

Once again: The FSU student and the UF student decide to do some radio astronomy and look at an intergalactic molecular cloud with their 30 meter dishes. They are looking at 60 micrometer light. What is the resolving power of each of these telescopes.

.5 arcseconds

The FSU student and the UF student decide to do some radio astronomy and look at an intergalactic molecular cloud with their 30 meter dishes. They are looking at 60 micrometer light. The decide that the resolution is not sufficient to see the details of the cloud. What can they do?

They each stay at home, but get a fast internet link, and link the outputs of the two radio telescopes together with a computer.

If you wanted to detect gamma ray radiation from a very violent stellar event, what would you do?

Write a proposal to NASA to get observation time on the Compton Telescope

All the terrestrial planets lie inside the asteroid belt


Pluto's orbit has the lowest inclination to the ecliptic of any planet.


One characteristic of the Terrestrial planets is their extensive moon systems.


All the planets' orbits are evenly spaced


Earth is nearly twice as large as Venus.


All the planets revolve around the Sun counter clockwise, except for Venus and Uranus.


All the planets orbit the Sun in exactly the same plane as the Earth


The two smallest planets, Mercury and Pluto, have no moons.(Assume Pluto is a planet!)


All four Jovian planets are thought to have cores larger than Earth.


All Jovian planets have rings around their equators and at least eight moons.


Pluto is more similar to the jovian planet's icy moons than to any of the other planets


Due to their great masses, all four Jovian worlds are much denser than the earth.


A Kuiper Belt object was recently discovered that may be larger than Pluto.

True (Eris)

Barringer Crater in Arizona is an example of a meteorite impact


Most astronomers now believe the demise of the dinosaurs 65 million years ago was caused by a large asteroid impacting the Yucatan peninsula area


Meteor showers are the result of collisions between asteroids.Meteor showers are the result of collisions between asteroids.


Carbonaceous asteroids contain fragile organic molecules


Many astronomers now regard Pluto as one of the thousands of Kuiper Belt bodies found beyond Neptune


Cometary dust tails lag behind the bluish ion tails as the comet rounds the Sun.


Most comets are believed to originate from the Oort Cloud


The Oort Cloud lies closer to the Sun than the Kuiper Belt


Researchers estimate that the total mass of the asteroid belt is about 1/10 that of the Moon's mass


Some meteorites are believed to have come from Mars and the Moon.


As a rotating gas cloud contracts, it spins faster


In the solar nebular theory, the dusty disk condensing around the Sun's equator became the ecliptic plane in which the planets then formed


In addition to revolving around the Sun counter clockwise, most planets also rotate on their axis counter clockwise.


Any successful model for the formation of the solar system must explain why the orbits of the planets have low eccentricities.


Astronomers have not yet been able to detect planets outside our solar system


We would expect other planets beyond our own solar system to orbit the equators of their home stars, as our own planets orbit the Sun.


In some cases, astronomers have detected extrasolar planets as they pass in front of their stars.


The magnetic field of the Earth probably arises from what process or condition?

A dynamo effect due to the motion of the electrically conducting molten iron core

Sunlight absorbed by the Earth's surface is re-emitted in the form of

Infrared Radiation

Planet X has a radius 10 times smaller than the Earth's radius, and a mass also 10 times smaller than Earth's mass. If you stand on Planet X, how much more or less would your weight be?

10 times more

The most likely theory for the formation of the moon is that it

formed from a sideways collision from a mars sized object

a plane traveling at 10 km is in the


Without the greenhouse effect operating in our atmosphere

Earth would have an average temperature of -23 degrees Celsius

Which of these gases is least abundant in our atmosphere


What is true of the Moon's orbital and rotational periods

they are equal

The Moon's near side always faces Earth due to

the earth's tidal force

What is true of spring tides?

The difference between low and high tides would be smallest

Which of these gets so bright as to be seen in daylight at times?


Which three worlds have almost identical densities

Mercury. Venus, and Earth

Which planet shows the widest range of surface temperatures between day and night?


How does Mercury's rotation rate relate to its orbit around the Sun?

Its rotation rate is 3/2 as long as its yer due to its tidal resonances

Venus' rotation

takes longer than its rotation around the sun

The atmospheric pressure on Venus

is 90 times higher than on Earth

What is the chief component of the Venusian atmosphere

Carbon dioxide

The chief gas in the martian atmosphere is

carbon dioxide

Why are Mars's seasons more extreme than those of the earth?

seas dried up long ago. axial tilt is slightly more than our 23.5 degrees. orbit is more eccentric than our almost circular one. weather is driven by evaporation from the polar ice in its summer.

Why doesn't Venus have a magnetic field?

its extremely low rotation doesn't produce a significant dynamo effect

In brightness (as seen from Earth), Jupiter is second only to the planet ________ most of the time.


In the telescope, ________ shows the most turbulent atmosphere with changes easily seen even with amateur telescopes.


The most famous and long lasting storm in the solar system is Jupiter's ________ spot

great red

Jupiter is largest and brightest in our skies when seen at


Adams and Leverrier predicted the position of ________, which Galle confirmed.


William Herschel discovered the green disk of ________ as the first telescopic planet.


While Saturn is almost as large as Jupiter, its mass is only about ________ of Jupiter's.

one third

The oblateness of the jovian disks is caused by their rapid ________.


Compared to the terrestrial planets, the Jovians have ________ average densities


Of the planets, ________ is the least dense, and could float on water


The oblateness of the Jovian disks refers to their ________ equatorial diameters, compared to the polar diameters.


Like Jupiter's, Saturn's rotation is fast and differential, with the ________ rotating fastest.


Unlike Jupiter and Saturn, at Uranus and Neptune the ________ rotates the slowest


In general, wind direction ________ between adjacent bands in Jupiter's atmosphere


Jupiter's bright zones are cloud streams made of ________ ice crystals


Jupiter's darker ________ are complex in color and origin, with complex organic molecules including carbon, sulfur, and nitrogen


The Great ________ Spot of Neptune was striking in 1989, but gone by 1995


Uranus and ________ are very similar in size, mass, and color.


The most abundant element (molecule) in Saturn's atmosphere is


________ looked very bland in Voyager 2 photos in 1986, but as equinox approached in the 1990s, its disk showed belts, zones, and storms


Because it has a higher percentage of ________, Neptune appears even bluer than Uranus


Compared to Jupiter, the element ________ is notably less common in Saturn's atmosphere, perhaps condensing to fall coreward as rain.


The mantles of Jupiter and Saturn are made of liquid metallic_________.


Jupiter emits twice the heat it gets from the Sun; the source of most of this energy is

gravitational contraption/ helium precipitation

While the rotation axis of _____________ is only tilted 29 degrees, its magnetic fields are just as strange as its twin's is.


Their magnetic fields should originate in the planets' ________, but those of Uranus and Neptune don't even come close.


Jupiterʹs magnetic field is produced in its rapidly spinning mantle of liquid

Metallic Hydrogen

What is thought to cause Io's volcanism?

tidal stresses from both Jupiter and Europa

The surface of Europa is most like the earth's

Arctic Ocean

The weak magnetic fields around Europa and Ganymede were found during flybys of


Of the Jovian satellites, which shows the oldest, most cratered surface


Which of these moons has the densest atmosphere?


For a moon the same density as its planet, the Roche limit lies at ________ times the radius of its planet


The Cassini Division is a gap in Saturn's rings caused by

Gravitational interaction with Mimas

What is the meaning of the solar constant?

the amount of energy that earth receives per unit area and unit time

The Sun's average density is almost exactly the same as


What two energy transport mechanisms, in order from outside the core to the surface, is found in the Sun?

radiative diffusion, convection

The solar winds blow outward from

Coronal holes

A loop of gas following the magnetic field lines between sunspots' poles is


As the Sun rotates, an individual sunspot can be tracked across its face. From eastern to western limb, this takes about

about two weeks

A maximum in solar activity should next occur about


What natural barrier must be overcome in order for two portons to collide and fuse together

electrostatic repulsion

In the proton-proton cycle, the helium atom and neutrino have less mass than the original hydrogen. What happens to the "lost" mass?

its is converted to energy E=MC^2

The solution to the solar neutrino problem which won a Nobel Prize in 2002 was

2/3 of the neutrinos decay into a new form in the 8 minutes to Earth

The speed of light is 3.00 × 10 m/s. If 2.00 kg of mass is converted to energy, how much energy will be produced?

1.80 × 10^17 J

A star has a parallax of .05 arc seconds, its distance is

20 parsecs

If spectroscopic luminosity classification gives us an estimated distance to the faint star SAO 47552 of about 3300 light years, then its parallax would be only

.001 arseconds

The stars α Cygni and β cygni are in the constellation Cygnus. Which statement can we claim is true?

α cygni appears brighter

Two stars both have parallaxes of 0.023", but star A has apparent magnitude +2.3, while star B is magnitude +7.3. Which statement is true?

Star A is both 100× brighter and more luminous than star B

The spectral type of a star is primarily a measure of its


Which of these stars would be the hottest?


What can be said with certainty about a red star and a blue star

The blue star is hotter than the red star

Which of these pairs of binaries would appear most similar in color telescopically

MIV and K9V

In general, what can be said about type O and B stars compared to type K and M stars

They are hotter and younger

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