Astronomy Midterm
Radioactive Decay
When isotopes are unstable and their nuclei are prone to spontaneous change, which causes breaking apart or having a proton turn into a neutron (Unstable Nuclei).
When the sun crosses the meridian, we call this...
local noon
What are the Geometric models?
made by Pythagoras - Earth centered models
What is the scientific method?
make observations -> ask a question -> suggest a hypothesis -> make a prediction ->perform a test -> if test supports hypothesis, make additional predictions -> if test doesn't support hypothesis, create new hypothesis
Galileo's contribution to astronomy included...
making observations and conducting experiments that dispelled scientific objections to the Sun-centered model
What determines whether an object will float or sink?
mass and size
Two stars that are in the same constellation...
may actually be very far away from each other
At approximately what time would you see a first quarter moon set?
midnight
When we turn on the fan (with no sail), the cart will...
move to the left of the lecture hall
From New Brunswick, some stars rise and set but others are visible all night. Where are the ones that remain visible?
near the north celestial pole
What are the phases of the moon in order?
new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, third quarter, waning crescent, back to new moon
If you see Polaris at the zenith, where are you on Earth?
north pole
When we turn on the fan with the sail in place, the cart will...
not move
The Sun is at its southernmost position on the celestial sphere..
on December 21
If earth were twice as far as it actually is from the Sun, the force of gravity attracting Earth to the Sun would be...
one-quarter as strong
Which property is very similar for all major planets in the Solar System?
orbit shape and orientation
What is NOT a characteristic that distinguishes Jovian from terrestrial planets?
orbital eccentricity
What is the ecliptic?
yearly path of sun around celestial sphere
At approximately what time would you see a third quarter moon on your meridian?
sunrise
Asteroids are most similar to what other type of objects in the solar system?
terrestrial planets
When the phase of the Moon is full, what happens to the Sun?
the Moon and Sun are on opposite sides of the Earth
The reason that we do not have a solar eclipse at every new moon is that...
the Moon's orbit is inclined relative to Earth's orbit around the Sun
The fact that we always always see the same face of the moon tells us that..
the Moon's rotation period is the same as it's orbital period
An observer at a fixed position on the Moon's surface would see..
the Sun rise and then set about two weeks later
The ecliptic is..
the apparent path the Sun follows on the celestial sphere during the course of a year.
In winter, Earth's axis points toward the star Polaris. In spring..
the axis also points toward Polaris
When I swing a ball on a string in a circle at a constant rate,...
the ball is accelerating toward me.
If you take the bus from here to Livingston campus, what will change?
the horizon
You can see a crescent Moon...
usually near the horizon
According to Kepler's third law...
Jupiter orbits the Sun at a faster speed than Saturn
How might our solar system be different if the frost line were much farther out?
Jupiter would not exist
What are the Outer planets?
Jupiter, Saturn, Uranus, and Neptune
Why didn't a terrestrial planet form at the location of an astroid belt?
Jupiters's gravity kept planetesimals from accreting into a planet there
Pluto is most similar to what type of objects in the solar system?
Kuiper belt objects
List out features of the terrestrial planets, except Earth.
Mercury - like our Moon Venus - extreme temperatures and pressure - thick C02 gas 470 degrees C. Mars - shows signs of water
What are the inner planets?
Mercury, Venus, Earth, Mars
What is the third Law of Planetary Motion?
More distant planets orbit the Sun at slower average speeds, obeying the precise mathematical relationship p^2=a^3, where p is equal to the planet's orbital period in years and a is the average distance from the sun in astronomical units
In space, objects are "weightless". How could you tell that a bowling ball is more massive than a golf ball?
Toss them to your lab partner and see which one is harder to throw
Which celestial object can never be seen on the meridian at midnight?
Venus
Before the time of interplanetary spacecraft, it was much harder to determine the mass of Venus than the mass of Mars. Why?
Venus does not have a moon, while Mars does.
Isotopes
When a chemical element is characterized by the number of protons in its nucleus but differs in the number of neutrons.
What does the force of gravitational attraction help to determine?
Halley's comet schedule and undiscovered planets
What are terrestrial planets?
Have an atmosphere of rock and metal
What are the ingredients of a solar nebula?
Hydrogen & Helium (98%) Hydrogen compounds Rock & Metal
Giant Impact
Hypothesis of how Earth got its moon.
What are Jovian planets?
"Jupiter-like" - have many moons all together
Recall the star trails photo. What can you say about when they were taken?
#1 was taken near the equator, while #2 was taken near a pole
If you start at the equator and move north, how does Polaris's position in the sky change?
It starts at the northern horizon and movies higher in the sky
What is Einstein's Solution?
-General theory of relativity - tested solar eclipse -people take his theory over Newton's - doesn't mean Newton was wrong, we just take the approximation
Many astronomers no longer regard Pluto as a true planet. What are persuasive reasons for this view?
-Pluto is quite similar to other Kuiper belt objects that have been discovered in recent years. - Pluto is unusually small for a planet in the outer solar system. - Pluto's orbit is more eccentric than that of any planet. - Pluto's orbit is more inclined to the plane of the solar system than that of any planet.
What is true during the northern hemisphere in the summer?
-Sunlight strikes the ground at a steeper angle in the Northern Hemisphere than in the Southern Hemisphere -The Sun follows a longer and higher path through the Northern Hemisphere sky than it does through the Southern Hemisphere sky
When you sit in class, there is a gravitational force between you and other students that is very small but not zero. What are true facts about this?
-You experience a force from every other student in the room. -Every other student in the room feels a force from you. -Each student feels the same force from you as you feel from him/her.
In order to be successful, a theory of planet formation must explain...
-the orderly motions of the planets. - why planets fall into two major categories. - why asteroids and comets reside where they do. - any exceptions to the general rules.
On how many days each year does the Sun reach zenith in New Brunswick?
0
What are the three processes of a solar nebula once it decreases in size?
1. Temperature increases 2. It spins faster as it shrinks 3. It's flattened into a disc
What are Newton's theories of gravity?
1. every mass attracts evey other mass through the force called gravity 2. strength of gravitational force attracting two objects is directly proportional to product of their masses - ex. doubling mass of one object, doubles force of gravity between two 3. strength of gravity between 2 objects decreases w/ square of distance btw centers. Follows inverse square law - ex. doubling distance = weakens force by factor of 2^2 or 4
What are the three statements Galileo claimed?
1. moving objects remain in motion unless a force acts to stop it (Newton's 1st law) 2. telescope - saw sunspots - no heavenly perfection 3. telescope - Milky Way - countless stars - stellar parallax - 4 moons orbiting Jupiter, not Earth
What are Newton's Laws of Motion?
1. objects at constant speed will remain at constant speed unless a force acts to change speed/direction 2. Force = mass X acceleration 3. For any force, there is always an equal and opposite reaction force
How does the parallax angle scale with the distance, d, to a star?
1/d
How many degrees is Earth's tilt from the sun?
23 1/2 degrees
What was the duration of the star trails photo?
24 hours
How much of the original element (tails) is left, on average, after two half-lives have elapsed?
25%
How many moons do terrestrial planets have all together?
3
Most main belt asteroids have orbits with semimajor axes between 2.1 and 3.3 AU. What is the range of their orbital periods?
3-6 yr
Suppose you find a rock that contains some potassium-40, a radioactive element that decays to argon-40 with a half-life of 1.3 billion years. A chemist determines that there are 5 grams of potassium-40 and 35 grams of argon-40 in the rock. How long ago did the rock solidify?
3.9 billion years
Suppose you traveled to a planet with 4 times the mass and 4 times the size of Earth. Compared to your weight on Earth, your weight on the other planet would be...
4 times smaller.
About how old is the solar system?
4.5 billion years
What is the gravitational constant?
6.67 X 10^-11 m^3 / (kg * s^2)
If you stand on the equator, what is the angle of the Sun from the horizon at noon on June 21?
66.5 degrees from the north
If you stand on the Tropic of Cancer (23.5° N latitude), what is the angle of the Sun from the horizon at noon on September 21?
66.5° from south
What are the times of sunrise and sunset?
6am, 3am, 12 am, 9pm, 6pm, 3pm, 12pm, 9am
Suppose a comet orbits the Sun such that its semi-major axis is 5 AU and the closest it gets to the Sun is 2 AU. At the point in its orbit when it is moving slowest, how far is the comet from the Sun?
8 AU
Suppose you find a planet that takes 27 years to orbit a star like the Sun. What is the semi-major axis of the planet's orbit?
9 AU
What has no net force exerted on it?
A car traveling at 70 miles per hour on a long straight interstate highway
What is an example of motion that is not accelerated?
A car traveling at 70 miles per hour on a long straight interstate highway
What is solar wind?
A stream of charged particles continually blown outward in all directions from the sun.
What is true about scientific theory?
A theory must explain a wide range of observations or experiments and even the strongest theories can never be proved true beyond all doubt
Suppose you swing a ball on a string around your head. What would happen if you let go of the string, and why?
According to Newton's first law of motion, the ball would fly off in a straight line.
What can you say about the motions of stars as seen from Earth's equator?
All stars rise and set
Describe the difference between a penumbra and an umbra?
An umbra is the shadow the sun casts off, where the portion of light is obscured by the occluding body. A penumbra is the region where the light is almost, or nearly obscured.
What is the second Law of Planetary Motion?
As a planet moves around its orbit; it sweeps out equal areas in equal times. So planets move faster when they are nearer to the Sun and slower when it is farther from the Sun
Why were the Greeks reluctant to let go of the Earth Centered universe?
Because of the stellar parallax, and its apparent shifting, which depended on distance, with nearer objects exhibiting greater parallax than more distant objects
Why was the concept of stellar parallax influential for the Greeks?
Because they thought the stars can't be that far away so Earth must be stationary.
Where are most of the known asteroids found?
Between the orbits of Mars and Jupiter.
Suppose the Sun suddenly turned into a black hole with the same mass. What would happen to the Earth?
It would stay in the same orbit at the same speed.
A famous picture of Earth was taken by one of the Apollo missions to the moon. When was the picture taken?
December
We can be sure that variations in Earth's distance from the Sun are not the cause of the seasons because...
Earth is always the same distance from the Sun
When we see Saturn going through a period of apparent retrograde motion, it means that...
Earth is passing Saturn at it's orbit, with both planets on the same side of the Sun
Earth is closer to the Sun in January than in July. Therefore, in accord with Kepler's second law...
Earth travels faster in its orbits around the sun in January than in July
How did Copernicus explain the apparent retrograde motion of Mars?
Earth's faster orbital speed allows it to overtake and pass Mars.
What causes the seasons?
Earth's tilt facing the sun
What is a supernova?
Explosion of a distant star
What is the difference between fact and theory?
Fact- something - something we consider true Theory - why we think it is true
What is the formula for gravitational attraction?
Fg = G * ((M1*M2)/(d^2))
What are major advantages of Copernicus's Sun-centered model over the Ptolemaic model?
If offered a more natural explanation for the apparent retrograde motion of planets in our sky and allowed calculation of the orbital periods and distances of the planets
What best describes the origin of the Jovian planets?
Initially gentle collisions between particles of ice and dust led to the build-up of massive cores which then captured a lot of hydrogen and helium.
What are special about Jupiter's moons?
Io - hot, volcanic Europa - icy, possible subsurface ocean
What is the leading theory for the origin for the Moon?
It formed from the material ejected by a giant impact on Earth
Suppose you discover a planet with a radius of 10^8 m and mass of 2x10^27 kg. What is the best hypothesis for the planet's composition?
It is composed mostly of light elements like hydrogen and helium.
What is unusual about Earth's moon?
It is quite large compared with its planet.
What's a frost line?
It marks the key transition between warm inner region of the solar system where terrestrial planets formed and the cool outer region where jovian planets formed. (Between Mars and Jupiter, Mars => Frost Line => Asteroid Belt => Jupiter).
What is true about scientific progress?
It progresses through the creation and testing of models of nature and it avoids explanations that invoke the supernatural
As seen from Earth, what would never show a crescent phase?
Jupiter
Mars has two moons called Phobos and Deimos. Which two pieces of information about the moons can be used to determine the mass of Mars?
Phobos's orbit has a semimajor axis of 9,400 km and a period of 7.66 hr.
What are planetesimals?
Pieces of planets.
Heavy Bombardment
Solar System history containing the three major collisions that occurred in the first few hundred million years.
What is the Nebular Theory?
Solar system formation because of an interstellar cloud (also called a nebula).
What's condensation?
Solid or liquid particles form in a gas.
The Sun rises in the east and sets in the west. Which of the following statements about the stars is true, as seen from New Brunswick?
Some stars rise in the east and set in the west, but others are visible all night.
Which of the three will have the greatest acceleration? (sponge, brink, lead)
Sponge
What was Aristarchus's view on the Sun and planetary motion?
Sun centered universe. But this was only accepted 2000 years later
What are the positions of the Earth, Moon and Sun during a Lunar Eclipse?
Sun, Earth in the middle, Moon
What are the positions of the Earth, Moon and Sun during a Solar Eclipse?
Sun, Moon in the middle, Earth
Why don't we have a solar or lunar eclipse every month, visible to us?
The Moon's axis around Earth is just above and Earth's tilt around the Sun is different
Why don't we see solar and lunar eclipses every month?
The Moon's orbit is tilted relative to the ecliptic.
An astronaut orbiting Earth aboard the International Space Station releases a paperclip and sees it float in the air. What is true about the gravity from Earth?
The astronaut experiences a larger force but the same acceleration as the paperclip.
How do the seasonal equinoxes work in the southern hemisphere? What happens to the sun?
The seasons are flipped from the northern hemisphere. There will be a time when the North Pole will have sunlight for 24 hours, and the South Pole will have complete darkness for 24 hours (and vice versa)
What happens when the diameter of a cloud is decreased by half?
The force of gravity is increased by a factor of 4.
What's accretion?
The general process by which particles stick together and grow larger.
What is true about half-life?
The half-life gets longer if we decrease the probability that an individual atom will decay in a fixed amount of time.
What is Occam's razor?
The idea that scientists should prefer the simpler view between the Copernican and the geometric view, that agree equally
Half-Life
The length of time it would take half its nuclei to decay.
Describe the position of the Moon and the Sun during a Total Lunar Eclipse (in relation to penumbra and umbra)
The moon is in the center of the umbra, from the Sun
Describe the position of the Moon and the Sun during a Partial Lunar Eclipse (in relation to penumbra and umbra)
The moon is on the cusp of the umbra, between both the penumbra and umbra, from the Sun
Describe the position of the Moon and the Sun during a Penumbral Lunar Eclipse (in relation to penumbra and umbra)
The moon is somewhere in the penumbra, from the Sun
Radiometric Dating
The most reliable method of measuring the age of a rock.
What is the first Law of Planetary Motion?
The orbit of each planet about the Sun is an ellipse with the Sun at one focus
What is the Solar Nebula?
The particular cloud that gave birth to our own solar system about 4.5 billion years ago.
What happens during the apparent retrograde motion of a planet?
The planet appears to move westward with respect to the stars
What does not follow from Kepler's laws of planetary motion?
The planets in our solar system have nearly circular orbits.
How does our theory of planet formation explain why the major planets lie in the same plane?
The solar nebula flattened into a disk before planets formed.
Suppose rock #1 has 20 grams of argon-40 and 20 grams of potassium-40, while rock #2 has 10 grams of argon-40 and 10 grams of potassium-40. What can you say about their ages?
The two rocks are the same age.
Eratosthenes needed 4 of the 5 pieces of information in order to estimate the size of the Earth. What was not important to know?
The well in Syrene was a certain depth
So what can we say about the force on the ball when I swing a ball on a string in a circle at a constant rate?
There is a net force toward me.
Suppose rock #1 has 20 grams of argon-40 and rock #2 has 10 grams of argon-40. What can you say about their ages?
There is not enough information to make definitive statements about their ages.
What best describes why the Greeks rejected the correct explanation for apparent retrograde motion?
They predicted if Earth orbited the Sun, then Stellar Parallax should occur, but they could not detect it
IF you drop four different trajectories of cannonballs, which will hit the ground first?
They will all land at the same time
Suppose you are an astronaut taking a space walk to fix your spacecraft with a hammer. Unfortunately, your life-line breaks and the jets on your backpack are out of fuel! How could you return safely to your spacecraft?
Throw your hammer away from the space ship.
What is special about Saturn's moon?
Titan - gaseous moon
Is there any debris left over from the formation of the solar system?
Yes, there is debris left over in the form of asteroids and comets.
You stand holding onto a pole near the edge of a merry-go-round that turns at constant speed. What best describes your motion?
You are accelerating because the direction of your motion is changing.
Suppose you stay up all night and see that stars don't rise and set—they all remain visible all night. What can you say about your location on Earth?
You are at either the north pole or south pole.
If you lean back and look straight up, you see the..
Zenith
Kepler made a major break from ancient beliefs when he...
abandoned circular orbits in favor of elliptical orbits
Who was Kepler?
abandoned the idea of perfect circles - used ellipses instead
What is a half-life in terms of number of repetitions?
about 1
What is the half-life if you change the decay probability (probability of heads) to 20%?
about 3 repetitions
In New Brunswick (latitude 40 degrees North), what is the highest point of the Sun in the Sky?
about 70 degrees from the horizon
An astronaut orbiting Earth aboard the International Space Station releases a paperclip and sees it float in the air. The paperclip is...
accelerating toward the Earth.
How many of the planets orbit in the Sun in the same direction that Earth does?
all of them
What is a hypothesis?
an educated guess - allows you to make a simple prediction
A geocentric model of the universe is...
any model that places Earth at the center of the universe
You stand holding onto a pole near the edge of a merry-go-round that turns at a constant rate. You..
are accelerating toward the center of the merry-go-round.
Judging from planetary compositions, where was the frost line in the solar nebula?
between the orbits of Mars and Jupiter
The apparent brightness of Mars changes as the planet moves around its orbit. According to the geocentric and heliocentric models, should Mars be at its brightest or faintest during the period of retrograde motion?
brightest/brightest
If you see the Moon setting at sunrise what phase is it?
full moon
What is the Copernican revolution?
calculated each planet's orbital and concluded that the Sun must be the center - People rejected this idea
The projections of Earth's rotation axis onto the sky are called the...
celestial poles
What is the astroid belt?
chunks of metal and rock that orbit Sun like planets but smaller between Mars and Jupiter
Tycho Brahe's contribution to astronomy included...
collecting data that enabled Kepler to discover the laws of planetary motion
Leftover ice-rich planetesimals are called...
comets
What are the scientific models?
conceptual representation whose purpose is to explain and predict climate changes
What is a zodiac? How many are there?
constellations around ecliptic. Traditionally 12, but actually 13.
What does the force of gravitational attraction NOT determine?
correct prediction for Mercury - it's the only exception
The Earth's rotation, its orbit around the Sun, and the Moon's orbit around Earth all go in the counter-clockwise direction as viewed from above Earth's north pole. In what direction does the Moon rotate?
counter-clockwise
What can you say about day and night in New Brunswick on March 21?
day and night are equal in length
In the northern hemisphere, stars rise in the _____ and set in the _____.
east/west
In the southern hemisphere, stars rise in the _____ and set in the _____.
east/west
Which of the following figures best illustrates the shapes of planetary orbits?
ellipse
If you see Polaris at the horizon, where are you on Earth?
equator
Planetary orbits are...
fairly circular and in the same plane
What is gravity?
falls toward core of earth - magnetic field
What will happen when we add salt to the water? The Pepsi/Diet Pepsi will...
float/float
What is the universal law of gravitation?
force of gravity mathematically explained
If there is going to be a total lunar eclipse tonight, then you know that the Moon's phase is...
full
What is the phase of the moon immediately before and after a lunar eclipse?
full
What is the major steps of the solar system formation?
gravitational collapse of the solar nebula, condensation, accretion
Suppose you see a crescent moon; how much of the Moon's entire surface (the full globe of the Moon) is in daylight?
half
Who was Tycho?
he saw a supernova, but still could not locate the stellar parallax, and concluded that the other planets revolve around the Sun - except Earth
What ingredients make up about 98% of the solar nebula?
hydrogen and helium
What is the celestial sphere?
imaginary "blanket-like" plane around plane
When Einstein's theory of gravity (general relativity) gained acceptance, it demonstrated that Newton's theory had been...
incomplete
If the EARTH's mass were doubled, the gravitational force of the SUN on the Earth would..
increase by a factor of two.
How does the half-life change if you add more coins?
it doesn't change
What is the Sun and what are influences?
it is the largest and brightest body in the solar system - covers 99.9% of our solar system it is influenced by temperatures and atmospheres
When it summer in Austrailia...
it is winter in the U.S.
What changes occur during a the collapse of a solar nebula?
it spins faster and heats up
What have more moons on average?
jovian planets
What is the Ptolematic model?
planets moves on small circle whose center moves around Earth on larger circle - also known as a EPICYCLE (small circle), and DEFERENT (larger circle)
What is retrograde motion?
planets usually move eastward through constellation, they occasionally reverse course, moving westward rather than eastward. It can last from a few weeks to a few months.
Try to determine the speed v and distance r from the Sun at the closest and farthest points of an orbit. Which of the following quantities is the same at the two points?
r * v
What are constellations?
region of the sky with well defined borders
What are comets?
rock and ice. grow tails as ice vaporizes and escapes in space
List the seasonal equinoxes (in the northern hemisphere) and their corresponding months when they arise
spring - March Fall - september Winter - December Summer - June
In Ptolemy's geocentric model, the retrograde motion of a planet occurs when...
the planet actually goes backward in its orbit around Earth
On the March equinox...
the two hemipsheres are equally illuminated
If you stand at the north pole, what is the angle of the Sun from the horizon on December 21?
there will be no sunlight. -23.5 degrees.
What is special about outer planets?
they have very gaseous compositions
Most Greeks rejected the heliocentric model of the solar system because...
they were not able to detect the stellar parallax that would be expected if Earth moves
One week after the full moon, the Moon phase is...
third quarter
The Big Dipper lies near the north celestial pole (it points to Polaris, after all). From what part of Earth's surface is the Big Dipper visible all night?
throughout most of the northern hemisphere
If you want to see the full moon rising, when and where should you look?
toward the east at sunset.
The Moon will be new on Sunday. If you want to see it now, when and where should you look?
toward the east before sunrise