ASTR 1010 Exam 1

Certain constellations are associated with certain times of year. Why do we not see Sagittarius in the Northern Hemisphere's winter or Gemini in the Northern Hemisphere's summer?

-in summer, when earth is turned away from sun (at night), we can see Sagittarius in the evening sky -6 months later-in winter-Sag is still in the same place on the celestial sphere -earth has moved to other side of its orbit -to look at Sag, one has to look toward sun-so its daytime -so we can't see it

Ellipses contain 2 axes: major and minor. Half the major axis is called the semimajor axis. What is especially important about the semimajor axis of a planetary orbit?

-it is the characteristic "size" of an ellipse in the way that a radius is the size of a circle

Gregorian/Julian calendar

-month-30-31 days -365 days of months -phase of moon not tied to time of month -every 4 years, add a leap year of 366 days

solar eclipse:

-new moon -moon must be on line of nodes

tied together:

-phase -time -where moon is

The vernal equinox is now in the zodiacal constellation of Pisces. Wobbling of Earth's axis will eventually cause the vernal equinox to move into Aquarius. How long, on average, does the vernal equinox spend in each of the 12 zodiacal constellations?

-precession carries vernal equinox around zodiac -takes 26,000 years for a full precession cycle -12-13 constellations in celestial sphere -assume spaced equally -vernal equinox spends 2000 years in each constellation

Galileo came up with the concept of inertia. What do we mean by inertia? How is it related to mass?

-property that matter has which allows it to resist acceleration -allows matter to move at a constant velocity -is proportional to mass

Copernicus

-resurrects heliocentric model -insisted on circular orbits and steady motion -brings back epicycles to account for differing velocities

How does our knowledge evolve over time?

-some scientific facts are not set in stone, but are liable to change as new data/observations reveal new information -science is free to change and not absolute like other disciplines -not everything is mutable or subject to interpretation

The southernmost star in a group of stars known as the Southern Cross lies at 65degreesS of celestial equator.What is the farthest north latitude for which the entire southern cross is visible? can it be seen in US?

-star can pass overhead if celestial latitude is the same as terrestrial latitude -southern cross passes over at 65degrees South -horizon is 90degrees from zenith -90-65=25 -overhead at 65degrees South, and on the horizon at 25degreesNorth -Hawaii -Puerto Rico -Florida Keys

The Moon's orbit is tilted about 5 degrees relative to Earth's orbit around the Sun. What is the highest altitude in the sky that the moon can reach, as in Philadelphia (latitude 40 degrees north)?

-summer solstice- sun is at highest point at noon -at tropic of cancer, sun is overhead on this day -phil is 40N -sun is not overhead at noon, but 17 degrees lower than the zenith -sun at maximum of 90-17=73 degrees -moon can be 5degrees above or below ecliptic -moon can reach 78degrees above horizon at most

What are the 2 conditions that must be fulfilled for a lunar eclipse to occur?

-the Earth must be between the Moon and the Sun -the line of nodes must point towards the Sun

Galileo

-use telescope for astronomical purposes -things in motion remain in motion at a constant speed

Hebrew calendar

-year of 12 or 13 months -intercalation-add 13th month every 2-3 years

What is the eccentricity of a circular orbit?

0

Convert to standard notation: 6.24X10^-5

0.0000624

Earth spins on its axis but wobbles like a top. How long does it take to complete one spin?

1 day

If a planet is 0.5 AU from the sun, what is the period of its orbit?

129 days

A pizzeria offers a 9 in diameter pizza for $12 and an 18 in diameter pizza for $24. Are both offerings equally economical? Which is a better deal?

18 in pizza

What is the approximate angular size of the Sun as seen from the Earth?

1900 arcseconds

If a star exploded in the Andromeda Galaxy, how long would it take that information to reach Earth?

2.5 million years

What is 0.00276 in scientific notation?

2.76x10^-3

Earth's tilt

23 degrees

Earth spins on its axis but wobbles like a top. How long does it take to complete one wobble?

26,000 years

Convert to scientific notation: 0.00346

3.46X10^-3

Suppose the tilt of the Earth's axis was 35 degrees instead of 23.4 degrees. At what latitude would the Sun be overhead on the Summer Solstice?

35 degrees

Suppose a new dwarf planet is discovered orbiting the Sun with a semimajor axis of 50 AU. What would be the orbital period of the new dwarf planet?

350 years

Convert to standard notation: 4.1X10^3

4,100

The average distance from the Earth to the moon is 384,000 km. How many days would it take you, traveling at 800 km/h-the typical speed of a jet aircraft-to reach the moon?

480 hours or 20 days

The surface area of a sphere is proportional to the square of its radius. How many times larger is the surface area if the radius is doubled?

4X bigger

What is the greatest angular distance that the Moon can deviate from the ecliptic?

5 degrees

Suppose you discover a planet around a Sun-like star. From careful observation over several decades, you find that its period is 12 Earth years. Find the semimajor axis.

5.2 AU

Convert to standard notation: 5.34X10^8

534,000,000

Convert to scientific notation: 7,000,000,000

7.0X10^9

If a planet is 4 AU from the Sun, its period must be

8 years

The surface area of a sphere is proportional to the square of its radius. How many times larger is the surface area if the radius is tripled?

9X bigger

The moon has a radius of 1,737 km, with an average distance of 3.780X10^5 km from earth's surface. The sun has a radius of 696,000 km, with an average distance of 1.496 X10^8 km from Earth. Show why the apparent sizes of the Moon and Sun in our sky are approximately the same.

-angular size of sun and moon are both 1900 arcseconds -that's why there are solar eclipses

Copernicus and Kepler engaged in what is called empirical science. What do we mean by empirical?

-based primarily on observations and experimental data -describes natural phenomena -rather than explain why they occur

Ptolemy

-best geocentric model -Almogest

Is there a location on the Earth where, over the course of a year, you see the entire sky? If so, where is it?

-equator -can see North and South Celestial poles towards northern and southern horizons -everything else is between these 2 points -can see all the stars in the sky in the course of a year

Aristarchos

-father of heliocentric model -sun is center of universe -disagreed w/ aristotle

lunar eclipse:

-full moon -moon must be on line of nodes

Aristotle

-if E moves around S, angle b/t stars should change-paralax effect -kills heliocentric -describes how things look

Islamic calender

-ignore sun -lunar calender only

What is the difference between a hypothesis and a theory in science?

-in common language, the words theory and hypothesis tend to have the same meaning-a type of guess not based on facts or observation -scientists reserve the word hypothesis for an educated guess or hunch about the way nature works -theory is reserved for hypotheses that have been thoroughly vetted by numerous experiments and consistency checks-usually requiring years or decades of work

Explain how the word theory is used differently in the context of science than in common everyday language.

-in common language, theory is a type of guess about how things work that is not based on facts or observations -scientists reserve the word theory for a well-developed and thoroughly tested set of ideas about how nature works

Galileo observed that venus had phases that correlated with its size in his telescope. From this information, you may conclude that Venus: A. is the center of the Solar System B. Orbits the Sun. C. Orbits Earth. D. Orbits the Moon.

B

An ellipse that has both foci in the same place is also known as...

a circle

Let's say an object is moving in a straight line at constant velocity. According to Newtonian mechanics, what must be applied to it to make it deviate from its straight-line motion?

a force

Approximately when is the Sun on the Vernal Equinox?

late March

Hipparchus

notices precession

sun moves _____ ____ each day on the _______.

one degree; ecliptic

The distance that Neptune has to travel in its orbit around the Sun is approximately 30X greater than the distance that Earth must travel. Yet it takes nearly 165 years for Neptune to complete 1 trip around the Sun. Why?

p^2=a^3

penumbra

partial shadow

umbra

shadow

synodic

solar

circumpotan stars

stars are set; dont travel around celestial pole

sidereal

stellar

solstice

sun stand-still

What is another name for the point that marks the intersection of the 0 degrees of celestial longitude (Right Ascension) with the celestial equator?

the First Point of Aries

The calendar that is currently used in the Western world is known as...

the Gregorian calendar

On what day of the year is the Sun lowest in the sky at noon from Athens, GA?

the Winter Solstice

The Sun reaches its highest point in the sky at noon from any location in the Southern Hemisphere on...

the Winter Solstice

Kepler's first law implies that:

the distance of a planet varies as the planet moves around the Sun

The path of the Sun along the celestial sphere is called...

the ecliptic

The Model of the Universe that puts the Sun right at the center is called...

the heliocentric model

The surface area of a sphere is proportional to the square of its radius. The radius of the Moon is only about 1/4 that of the Earth. How does the surface area of the moon compare with that of the earth?

the moon's surface area is 1/16 that of the earth

In a geocentric system, the retrograde motion of the outer planets is explained by having...

the outer planets move on epicycles

If a planet is at its perihelion distance from the Sun, which of the following statements is true?

the planet is closest to the Sun and moving most quickly

You can define the length of the day with respect to the Sun. What other reference point(s) can be used to define the length of day?

the stars

What is the reason Aristotle gave for choosing the geocentric system over the heliocentric system?

the stars do not show a parallax shift over many months

mechanics

theory of motion

What is peculiar about the motion of the inner planets?

they are never very far from the Sun in angular distance

When the Earth is directly between the Sun and the Moon, what is the phase of the Moon?

full

Gasoline is sold by the gallon in the U.S. and by the liter nearly every else in the world. There are approximately 3.8 liters in a gallon. If the price of gas is $4 per gallon, how much does it cost per liter?

$1.05 per liter

Celestial sphere

-2D field -puts us at the center of the universe

The tilt of Jupiter's rotational axis is 3 degrees. Explain how Earth's seasons would be different if Earth's axis had this tilt.

-3 degree tilt would be so small there would be no seasonal changes -sun would allow same trajectory in the sky for a given location day after day -it would not be significantly higher in summer than winter

Suppose the tilt of Earth's equator relative to its orbit were 10degrees instead of 23.5. At what latitudes would the Arctic and Antarctic Circles and the Tropic of Cancer and Capricorn be located?

-Arctic circle would be at north latitude 80 -and Antarctic would be at south latitude 80 -Tropics of Cancer and Capricorn would be 10 above and below equator

Which people were involved in the Copernican revolution?

-Galileo -Isaac Newton -Tycho Brahe -Johannes Kepler

Which of the following points on the celestial sphere changes its location because of precession?

-North Celestial Pole -South Celestial Pole -the Summer Solstice -the Winter Solstice

Kepler's laws

1. planets orbit the sun in elliptical orbits with sun at one focus 2. equal areas of an orbit are covered in equal times 3. period is related to distance

Newton's laws of motion

1. things in motion continue in motion at constant velocity unless a force acts on them 2. F=ma 3. For every action, there is an equal and opposite reaction

Convert to scientific notation: 1,238

1.238X10^3

The surface area of a sphere is proportional to the square of its radius. The radius of the moon is only about 1/4 that of Earth. How does the surface area of the moon compare with that of the Earth?

1/16 that of the Earth

The surface area of a sphere is proportional to the square of its radius. How many times larger is the surface area if the radius is halved (divided by 2)?

1/4 of the size

During the latter half of the 19th C, a few astronomers thought there might be a planet circling the Sun inside Mercury's orbit. They even gave it a name, Vulcan. We now know that Vulcan does not exist. If a planet with an orbit 1/4th the size of Mercury's actually existed, what would be its orbital period relative to that of Mercury?

1/8

The surface area of a sphere is proportional to the square of its radius. How many times larger is the surface area if the radius is divided by 3?

1/9 of the size

Which of the following Greek astronomers/philosophers believed that the Sun was at the center of the Universe?

Aristarchus

What is the name of the ancient Greek who figured out how big Earth was?

Eratosthenes

Kepler's 1st law replaced Copernicus's perfect circles with ellipses, thus shattering the idea that: A. Tycho's data were accurate B. the Sun is at a focus C. the heavens were perfect, with perfectly round objects and perfectly round orbits D. Earth goes around the Sun

C

Galileo observed that Jupiter has moons. From this information, you may conclude that: A. Jupiter is the center of the Solar System B. Jupiter orbits the Sun. C. Jupiter orbits Earth. D. some things do not orbit Earth.

D

Suppose you read the newspaper that a new planet has been found. Its average speed in orbit is 33km/s. When it is closest to its star it moves at 31 km/s, and when it is farthest from its star it moves at 35 km/s. This story is in error because: A. the average speed is far too fast B. Kepler's third law says the planet has to sweep out equal areas in equal times, so the speed of the planet cannot change C. Planets stay at a constant distance from their stars; they don't move closer or farther away D. Kepler's second law says the planet must move fastest when it's closest, not when it's farthest away. E. Using these numbers, the square of the orbital period will not be equal to the cube of the semimajor axis.

D

Kepler's Second Law says that: A. Planetary orbits are ellipses with the Sun at one focus B. The square of a planet's orbital period equals the cube of its semimajor axis C. for ever action there is an equal and opposite reaction D. Unbalanced forces cause changes in motion E. Planets move fastest when they are close to the sun.

E

In the 16th century, the heliocentric system was first re-proposed by...

Nicolaus Copernicus

Each ellipse has 2 foci. The orbits of the planets have the Sun at one focus. What is at the other focus?

Nothing

If the Sun suddenly exploded, how soon after the explosion would we know about it?

a little more than 8 minutes

The speed of a planet in its orbit varies in its journey around the Sun. At what point is the planet moving slowest?

aphelion

The speed of a planet in its orbit varies in its journey around the Sun. At what point in its orbit is the planet moving fastest?

at the perihelion point of its orbit

Brahe

best data of planetary positions

Diurnal motion

daily

Stars rise in the _____ and set in the _______. The highest point is due _______.

east; west; south

Kepler's laws are examples of what type of science?

empirical

Kepler's Second Law states that

equal areas of an orbit are swept out in equal times

Eratosthenes

figured out size of earth

In addition to making crucial contributions to the Laws of Mechanics, Galileo also...

first used the telescope to make many astronomical discoveries

How long is a synodic month?

from one full moon to the next full moon

What is the difference between the mass and weight of an object?

weight is a force and depends on the local acceleration, while mass is a quantity that stays the same