AST 10G Qualitative Questions

What is the distance measuring technique for the following: Nearby stars, Milky Way & Nearby Galaxies, Nearby galaxies & distant galaxies?

1. Stellar Parallax 2. Variable Stars 3. White dwarf supernovae

Factoring in everything we currently know about the history of the universe, our best estimate for the age of the universe is

13.8 Billion Years

Objects orbiting around the center of the Milky Way obey Kepler's 3rd Law. This means that:

A cloud of gas or star that is further from the center will generally take more time to orbit

When astronomers say that the universe is homogeneous, they mean that

A given volume of space is composed and behaves much like any other volume of space at the same redshift or distance

How do astronomers know that there aren't significant amounts of dark matter within our solar system?

A lot of dark matter would affect the motions (orbits) of our spacecraft as they move through the solar system, and we see no such effect

What, produced at the core of the Sun, will take the shortest time to emerge from the Sun's photosphere (surface)?

A neutrino

In the very distant future, given our best model of the accelerating universe, what will the universe look like?

All the stars will die and the galaxies will be dark

In the future, several students living on board a space station decide to have a race among different types of electromagnetic radiation. Which radiation travels through space the fastest?

All travel through space at the same speed

The size of the device that collects radiation (such as light) is called a telescope's:

Aperture

According to the models of the universe we discussed in this course, why do the galaxies move apart (why do we have Hubble's law)?

As a result of the Big Bang, space itself is stretching, and this stretching carries the galaxies away from each other

In our modern view of the expansion of the universe, we understand that it is space (or, more precisely, spacetime) that is stretching; individual galaxies don't speed away from each other as if they were rockets. In this view, why do galaxies show a redshift?

As space stretches, the waves of radiation in space also stretch and their wavelength increases

Which of the following statements about dark matter is FALSE:

Astronomers have a pretty good idea what the dark matter is made of

A spectral line associated with a particular element is measured in the lab to be at a wavelength of 570.2 nm. An astronomer measures it in Star Y's spectrum at a wavelength of 571.0 nm, and in Star Z's spectrum at a wavelength of 570.6 nm. How can you best describe what is happening?

Both stars are moving away from us, with Star Y receding faster.

According to our current understanding, giant elliptical galaxies form:

By the merger (or swallowing) of a number of smaller galaxies in a cluster of galaxies

Today, we believe that only a small number of elements were actually formed during the Big Bang. Which of the following was NOT one of these:

Carbon

What about different types (shapes) of galaxies is correct?

Collisions and mergers between galaxies can sometimes change a galaxy's type (shape)

After a nice dinner around the campfire on a camping trip, you and a friend decide to get away from the fire to observe the stars. As you get farther and farther away, you see the brightness of the fire:

Decrease as the distance squared

What best describes how the composition of Earth compares to the composition of the Sun?

Earth is composed of elements that are much heavier than the elements that make up the Sun, which explains Earth's higher density.

What is NOT true about the Earth's position with respect to the Sun?

Earth is immersed in the Sun's nuclear reaction.

The type of galaxy that consists almost entirely of old stars and is thus less blue (more yellow and reddish) than the other types is:

Elliptical

If you are in a freely falling elevator near the top of a tall building, as the elevator falls, your weight would be:

Equal to zero - you would be weightless

Where in space did the expansion of the universe begin?

Everywhere at once

After the core of a massive star becomes a neutron star, the rest of the star's material

Explodes outward as a supernova

True or False - Galaxies within groups or clusters are currently dispersing as stretching space pulls them apart

False

True or False - Planets in the solar system are gradually being pulled away from each other

False

What method would astronomers use to find the distance to a galaxy so far away that individual stars are impossible to make out (resolve)?

Finding the redshift and using Hubble's Law

Astronomers believe that the large elliptical galaxies formed

From the collision and merger of many smaller fragments

You discover two galaxies, which you call Galaxy A and Galaxy B. You carefully measure their angular sizes, and discover that both galaxies have the same angular size. When you measure their distances away from you, you find that Galaxy A is farther away from you than Galaxy B. Which galaxy has a larger physical size? Explain your answer.

Galaxy A. Angular size is defined as the size of an object from the point of observation. If Galaxy A is further away than Galaxy B but has the same angular size, this is due to its size being bigger and it thus being able to maintain the 'same size' as Galaxy B from the same point of observation. If Galaxy A were smaller, than as its distance is further away, Galaxy A would have a smaller angular size than Galaxy B.

Electromagnetic radiation is generally divided by scientists into bands according to wavelength. Order by wavelength, from shortest to longest.

Gamma Rays, Ultra Violet, Visible Light, Infrared, Radio

A team of astronomers takes spectra of thousands of different stars in different parts of the sky. The spectra show significant differences. The main reason the spectra of the stars do not all look alike is that the stars

Have different temperatures

When astronomers refer to "lookback time," what are they referring to?

How far back in time we are seeing a particular object in the universe when we collect its image using a telescope.

The star Sirius looks the brightest to people in the Northern Hemisphere out of all the stars in the night sky. Suppose we put Sirius 10 times further away. How much dimmer would Sirius appear to us (that is, how much lower would the light intensity be)?

How much dimmer = 100.0100.0times

What is a way that having an active galactic nucleus (AGN), with a supermassive black hole in the center, can affect the development of a galaxy?

Huge energetic jets from the accretion disk can disturb and lessen star formation in the galaxy

The most common element in the Sun is

Hydrogen

Where would you look for the youngest stars in the Milky Way Galaxy?

In the disk

Which factor plays the most significant role in making it difficult to study the structure of the Milky Way in detail?

Interstellar dust and gas

Put the following in order of how abundant they are in the universe (how much of the universe they make up), starting with the least abundant to the most abundant: Matter inside stars, Atoms in living things, Dark energy, Dark matter, Ordinary matter

Least: 1. Atoms in living things 2. Matter inside stars 3. Ordinary matter 4. Dark matter 5. Dark energy

Why is the use of Hubble's Law to measure distances to galaxies so important to astronomers?

Most galaxies are so far away, the only way to get distances to them is to use Hubble's Law

If you chose an isolated spiral galaxy at random and were able to watch it for the entire lifetime of the universe, is it guaranteed to become an elliptical galaxy?

No; cosmological expansion could keep an isolated galaxy from ever encountering other massive galaxies but its color would eventually get redder as star formation winds down.

When a large nucleus breaks apart (or is broken apart) into two smaller pieces, this is called

Nuclear Fission

Today we realize that the source of energy for the Sun is a process called

Nuclear Fusion

The Sun is an enormous ball of gas. Left to itself, a ball of so many atoms should collapse under its own tremendous gravity. Why is our Sun not collapsing?

Nuclear fusion in the core keeps the temperature and the pressure inside the Sun at a high enough level so that gravity is balanced

A graduate student in astronomy needs to measure the mass of a spiral galaxy she is studying for her PhD thesis. Which of the following observations would be important for her to make?

Obtain the speed at which stars or gas near the outer regions of the galaxy are moving around

When energy is produced and released by the Sun's core, it leaves the core in the form of

Photons

Put the following parts in order from smallest to largest: The Milky Way Galaxy, Globular Cluster M13, The Solar System, The Perseus Spiral Arm, The event horizon of the blackhole at the center of the Milky Way galaxy

Smallest: 1. The event horizon of the blackhole at the center of the Milky Way galaxy 2. The Solar System 3. Globular Cluster M13 4. The Perseus Spiral Arm 5. The Milky Way Galaxy

What did NOT happen during the first few minutes after the Big Bang?

Some very massive early stars formed

Which of the following is pretty good evidence that the universe began with a Big Bang?

The 3-degree cosmic microwave background radiation

What is NOT an advantage that the Hubble Space Telescope has over large telescopes on Earth?

The Hubble has a larger aperture than any visible-light telescope on Earth

What correctly explains why fission is not an important source of energy in the Sun?

The abundance of heavy elements that would split in fission is much too low.

How do astronomers currently think the amount of detectable (observable) matter in the universe compares to the amount of dark matter and dark energy?

The amount of detectable matter is far less than the amount of dark matter & energy

Two merging galaxy groups centered on elliptical galaxies SDSSCGB 8842.3 and SDSSCGB 8842.4, which all appear to be working together to gravitationally lens at least two bright background galaxies. In such a lensing arrangement, the lensed objects are in the background, at a much greater distance than the objects performing the lensing. If, therefore, the large ellipticals are in the foreground (implying less redshifting) and the lensed galaxies are in the background (implying more redshifting), why do the background galaxies still have a bluer appearance? Choose the best explanation.

The background galaxies were forming stars at such a high rate, producing so much UV light, that even significant redshifting still left them brightest in blue wavelengths.

What correctly explains why it takes light a long time to escape the Sun?

The density inside the Sun is incredibly high and photons are scattered by particles too easily to travel far.

When a knowledgeable amateur astronomer tells you that she has a 14-inch telescope, what does the number 14 refer to?

The diameter of the primary lens or mirror

What observation in astronomy, made AFTER the discovery of quasars, was a big help to astronomers in figuring out what quasars really were?

The discovery that the Milky Way Galaxy has a black hole at the center with enough mass for 4 million Suns

What best explains why the James Webb Space Telescope was optimized for infrared viewing in order to study early galaxy formation in the universe?

The earliest galaxies are the most distant, and universal expansion has redshifted their spectra into infrared wavelengths.

Edwin Hubble was able to show that (with the exception of our nearest neighbors) the farther a galaxy is from us, the

The faster it is moving away from us

An astronomer is observing a distant galaxy which looks blue. What can she conclude from this observation?

The galaxy must have a lot of star formation going on at the time we are seeing it

With enormous effort, a team of astronomers manages to collect enough light from a galaxy far, far away to produce a spectrum. That spectrum has lines from the elements carbon, silicon, and sulfur. This tells the team that

The galaxy must have had an entire generation of stars that was born, lived, and died

Once a black hole forms, the size of its event horizon is determined by

The mass inside the event horizon

Recent observations indicate that the universe is expanding faster today than it was a few billion years ago (that, in other words, the expansion of the universe is accelerating.) What kind of observations have led astronomers to this surprising conclusion?

The measurement of galaxy distances using white dwarf (type Ia) supernovae

Suppose two stars have the same apparent brightness but one is more distant than the other. What can you say about these two stars relative to each other?

The more distant star is more luminous.

What is evidence that the formation process of our Galaxy may have included collisions with smaller neighbor galaxies?

The observation of long moving streams of stars that continue to orbit through our Galaxy's halo

According to Einstein's general theory of relativity, the stronger a star's gravity,

The slower time runs near it

Where in the universe have astronomers NOT found evidence for the presence of dark matter today?

The solar system

An astronomer is studying galaxies of stars that are very far away and thus look extremely faint (using visible light). What kind of telescope should she and her graduate students apply for time on?

The telescope with the biggest aperture possible

(In the absence of a strong magnetic field), what is the chief factor that determines what type of electromagnetic radiation objects give off:

Their temperature

The reason white dwarf (type Ia) supernovae are useful to astronomers for determining distances to other galaxies is that

They are very bright, and generally reach the same peak luminosity

How do astronomers measure the mass that the Galaxy contains inside the orbit of the Sun?

They measure the distance to the center of the Galaxy and the period of the Sun's orbit and then use Kepler's Third Law

How do astronomers know what the outer layers of the Sun are made of?

They take an absorption line spectrum of the Sun, and the absorption lines tell us what elements are present in the outer layers

Your sweetheart gives you a piece of gold jewelry as a present to celebrate your passing your astronomy class. Where might some of the gold atoms in that gift originally come from (where were they most likely made)?

They were built up from smaller nuclei during a supernova explosion

The Andromeda Galaxy (our nearest spiral neighbor) has spectral lines that show a blueshift. From this we may conclude that:

This particular nearby galaxy is moving toward us

True or False - Galaxy groups and clusters are carried along with stretching space

True

True or False - The Milky Way's gravity holds it together as space expands beyond it

True

What have we learned from the work of Harlow Shapley and others about the location of the Sun in the Milky Way Galaxy?

We are in the disk of the Galaxy, about 3/5 of the way from the center

The force of gravity is an inverse square law. This means that, if you double the distance between two large masses, the gravitational force between them

Weakens by a factor of 4.

What scenario correctly demonstrates the transformation of mass into energy as given by Einstein's equation, E=mc2?

When hydrogen is fused into helium, the mass difference is turned into energy.

When a single star with a mass equal to the Sun dies, it will become a

White dwarf

Astronomers know that stars can evolve from one type into another, so it seems natural to wonder the same thing about galaxies. Can spiral galaxies turn into elliptical galaxies?

Yes; if a spiral galaxy interacts with another large galaxy then a flurry of star formation happens, which can use up all of the gas and eventually lead to a "red and dead" stellar population. Yes; if a spiral galaxy interacts with another large galaxy this will disrupt its structure and result in a stellar population that orbits in all directions.

Before you can use Hubble's Law to get the distance to a galaxy, what observation must you make of that galaxy?

You must take a spectrum of the galaxy and measure the redshift