AST 1002 Final Exam

astronomy defintion

patterns among the stars

one light-year(distance) equals

one calendar year(time)

how many stars are in the Milky Way?

100 billion

If there are 6000 stars in the sky, how many could you see with an uninterrupted view?

3000

the early universe was comprised of what two elements?

hydrogen and helium

the most massive elements were formed

inside stars and supernovae

the cosmological principle states that

the universe looks the same everywhere as long as you look on large enough spatial scales

What is a basic unit of mass in the metric system?

a gram

theory definition

guess or hypothesis

a simple observation or experimental result is

a fact

Put in correct order from nearest to furthest
Virgo Supercluster
The Solar System
The Milky Way
Earth
The Universe
The Local Group

5. Virgo Supercluster
2: The Solar System
3: The Milky Way
1: Earth
6: The Universe
4: The Local Group

The nightly motion of objects across our sky is caused by the

rotation of earth on its axis

Yes. On a summer night many of the constellations you can see are different from the constellations you can see on a winter night. But there are some constellations you can see all year long.

are constellations seasonal?

Which of the following statements best represents the overall rationale for scientific investigation?

Reality is comprehensible, and a limited number of fundamental principles governs the nature and behavior of the universe.

The scientific method is a process by which scientists

gain confidence in theories by failing to prove them wrong

If the star Polaris has an altitude of 35° then we know that

our latitude is +35 degrees

The apparent path of the Sun across the celestial sphere during a year is called the

elliptical plane

If you go out at exactly 9 P.M. each evening over the course of one month, the position of a given star will move westward by tens of degrees. What causes this motion?

revolution of earth around the sun

Winter Solstice

1. longest period of darkness
2. altitude of sun is least
3. sun sets furthest west

tilt of sun is responsible for:

1. variation in directness of sun rays
2. variation in length of day

If you were going to send a spacecraft to circle the Moon and photograph the entire far side (the side not visible from Earth), during which lunar phase (as seen from Earth) would you do the photography?

new moon

total lunar eclipse is visible in principle (assuming clear skies everywhere)

to everyone in one hemisphere

why don't we have solar and lunar eclipses every month?

Because the Moon's orbit around Earth is tilted by about 5° out of the ecliptic

Kepler's First Law

1. describes the shape of planetary orbits as ellipses
2. places the sun at the focus of the ellipse rather than at the center

Kepler's Second Law

the speed of a planet is greatest when closest to the sun

Kepler's Third Law

the semimajor axis of the orbit is 4 AUs then the orbit period is 8 years

velocity

distance divided by time with direction

speed

distance divided by time without direction

force

this, if unbalanced, will cause an object to accelerate

acceleration

a decrease in speed is an example of this

inertia

This property of an object is greater if the mass of the object gets bigger

Select the discoveries Galileo made by making astronomical observations through a telescope.

1. craters of moons
2. Jupiter's moons
3. phases of Venus

a comet on an elliptical orbit has a speed greatest when

near the sun

If the distance between the Earth and Sun were cut in half, the gravitational force between these two objects would:

increase by 4

What types of electromagnetic radiation from space will reach the surface of Earth without being significantly absorbed by the Earth's atmosphere?

visible lights and radio waves

All forms of light have what property in common?

all forms of light are electromagnetic radiation

What is the one fundamental difference between X rays and radio waves?

The wavelengths of X rays and radio waves are very different.

By what factor is the amount of light gathered by the 10-m diameter Keck telescope on Mauna Kea, Hawaii, greater than that gathered by the 2.5-m diameter Mount Wilson telescope?

16

why was adaptive optics developed

to compensate for image distortion caused by Earth's atmosphere

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

reduce atmospheric blurring

Order the different types of electromagnetic waves in increasing frequency.

1. Radio
2. Microwave
3. Infrared
4. visible
5. ultraviolet
6. x-rays
7. gamma rays

The overall shape of the orbits of most of the planets in the solar system is

slightly elliptical but not nearly circular

The most probable time sequence for the formation of the solar system was the following:

The Sun contracted first as a gas ball, and the planets and moons formed shortly afterward by accretion and condensation.

How much mass was there in the protoplanetary disk out of which the planets formed, compared to the mass of the Sun? `

less than one percent

What happens to the gravitational energy of gas as it falls toward and eventually hits the accretion disk surrounding a protostar?

it is converted into thermal energy, heating the disk

main difference between terrestrial and giant planets

terrestrial planets are closer to the sun

Strong evidence for the existence of planetary systems in the process of formation around other stars comes from

photographs and infrared observations of disks of dust

What ionizes the gas in a planetary nebula and makes it visible

ultraviolet photons emitted by a white dwarf

The gas in a planetary nebula is composed of

hydrogen and elements processed in the core of the post-asymptotic giant branch star

One star in a binary will almost always become a red giant before the other because

small differences in main-sequence masses yield large differences in main-sequence lifetimes

A nova is the result of which explosive situation?

mass transfer onto a white dwarf

What occurs if a white dwarf exceeds the Chandrasekhar limit

a type 1a supernovae explosion

If you measure the average brightness and pulsation period of a Cepheid variable star, you can also determine its

distance

The CNO cycle in high-mass main-sequence stars burns ________ to ________in their cores

hydrogen; helium

When the core of a massive star collapses, a neutron star forms because:

protons and electrons combine to form neutrons

Which of the following is true about the instability strip on the H-R diagram?

stars show variability in their brightness
evolved stars pulsate
location of RR Lyrae and Cepheids

Why does the luminosity of a high-mass star remain nearly constant as the star burns heavy elements in its core, even though it is producing millions of times more energy per second than it did on the main sequence?

most of the energy is carried out of the star by escaping neutrinos

Essentially all the elements heavier than iron in our galaxy were formed

by supernovae

A neutron star contains a mass of up to 3 M☉ in a sphere with a diameter approximately the size of

a city

What is the radius of the event horizon of a 10 solar mass black hole?

30km

Hawking radiation is emitted by a black hole when:

a virtual pair of particles is created from the vacuum of space.

Gravitational lensing occurs when ________ distorts the fabric of spacetime

any massive object

we classify all galaxies as

how they appear in the sky

The disks of spiral galaxies appear blue because:

spiral galaxies are still undergoing star formation

Light is increasingly redshifted near a black hole because:

time is moving increasingly slower in the observer's frame of reference.

Active star formation does not occur in elliptical galaxies because they:

contain little molecular hydrogen

What does the Hubble tuning fork illustrate?

a classification theme

Why does the central bulge of a spiral galaxy appear red when compared to the color of the spiral arms?

There is no star formation there, and the star population is dominated by old, long-lived, low-mass red stars.

Besides shape, what characteristic clearly separates elliptical galaxies from spiral galaxies?

color

What is observed to happen to the velocities of stars that reside at greater distances from the center of the galaxy?

they essentially stay the same

Why is 21-cm radiation a good spiral arm tracer?

Emitted by neutral hydrogen, it traces the location of concentrations of gas.

Why do rotation curves of galaxies imply that dark matter exists?

The velocity of stars stays somewhat constant at distances beyond the visible edges of galaxies, implying that more matter than what we observe in stars and gas must be there.

AGNs appear to be powered by:

supermassive black holes

How do we know that AGN have sizes on the order of our Solar System?

the brightness varies on timescales of hours to a day

Why is 21-cm radiation the best way to map the spiral arms in the Milky Way?

These photons, which are produced by neutral hydrogen, penetrate the dense clouds of gas and dust in the disk.

Harlow Shapley showed that ________ form a spherical halo that is not centered on the Solar System, disproving the idea that the Sun was the center of the Milky Way Galaxy.

global clusters

In which part of the Milky Way would you find little or no neutral hydrogen, no current star formation, and stars that are older than 10 billion years?

the halo

Observations of Doppler shifts toward the center of the galaxy show on one side hydrogen clouds are blueshifted while on the other side hydrogen clouds are redshifted. This is the pattern of the rotation velocity of a:

disk

Why do we know that at least one generation of stars formed and died before the Milky Way's globular clusters formed?

no global cluster has zero heavy elements

How have astronomers measured the mass of the black hole at the center of our galaxy?

by observing the motions of stars near the center of the galaxy

The chemical composition of a star's atmosphere tells us:

the chemical composition of the cloud from which the star formed.

Because of the general expansion of space, all distant galaxies appear to be moving away from us, with speeds that increase with distance from our Galaxy. Observers in one of these distant galaxies would apparently see all galaxies

moving away from them, the more distant galaxies moving faster.

The cosmological redshift of galaxies is explained best as

space itself expanding with time, stretching light

Why can Type Ia supernovae be used to determine a galaxy's distance?

Type Ia supernova have approximately the same luminosity

Where in the universe did the Big Bang take place?

everywhere in the universe

After the Big Bang, as the universe cooled and protons and electrons combined so that the universe became neutral, what important consequence happened?

photons began to travel freely through the universe

What is it that keeps localized regions of space, such as things on Earth, planetary systems, star clusters, and whole galaxies, from participating in the general expansion of the universe?

mutual gravitational attraction between objects in these systems

The existence of the cosmic microwave background radiation tells us that the early universe was:

much hotter than it is today

If the fate of the universe were determined SOLELY by what we currently know to be the total mass of the universe in luminous and dark matter (excluding dark energy), astronomers would predict that we live in a universe that will:

expand forever

Why does the overall mass and energy density of the universe decide its ultimate fate?

The greater the density of the universe, the more gravitationally bound the universe will be.

A grand unified theory unites which forces?

only electromagnetism, weak nuclear, and strong nuclear

Our current ideas on galaxy formation suggest that the visible parts of galaxies:

form only in the densest parts of dark matter halos.

In the 1990s, astronomers found that distant Type Ia supernovae were ________ than they expected, leading them to conclude that ________.

fainter; the universe's expansion rate has been increasing with time

Stars of the first generation were

more massive than today's average star

The fact that we do not observe any stars with chemical compositions matching our predictions for the very first generation of stars implies:

the first stars died quickly, which implies a high mass

Why is it highly likely that life, should it exist elsewhere in the universe than just on Earth, would be based on carbon chemistry?

Carbon can bond with many more atomic species in a wider variety of complex forms than other equivalent elements, such as silicon.

Venus and Mars have little free oxygen in their atmospheres. What has allowed Earth to have a large amount of oxygen in its atmosphere?

cyanobacteria and other photosynthesizing organisms

What is the evidence that galaxies can merge?

Galaxies at higher redshifts are smaller and more irregularly shaped.
Simulations show that mergers produce observed galaxy shapes.
Hubble Space Telescope has observations of merging galaxies.

Which one of the following is NOT one of the six chemical elements commonly found in living organisms?

helium

We search for intelligent life in the universe by:

using radio telescopes to search for radio signals