exam 4 study guide

Select all the correct statements about William and Caroline Herschel.

-They discovered that most of the stars in our Galaxy are distributed in a flattened structure. -They concluded that the Solar System is at the center of the Galaxy.

Select all the characteristics typical of Population II stars

-They have low metallicity values (i.e., they are poor in elements heavier than H and He). -They are made of old stars (typically 11-13 Gyr old)

Dark matter in clusters of galaxies (like the one shown below) is detected ...

-by observing gravitational lensing of galaxies located behind the cluster. -by measuring the velocities of galaxies

Compared to current nearby galaxies, early galaxies ...

-were bluer in color -were more numerous

Put in chronological order starting from the beginning the following events in the history of the universe.

1. Big Bang 2. unification of fundamental forces 3. annihilation and pair production 4. primordial fusion of hydrogen into helium nuclei 5. formation of neutral atoms 6. formation of first stars 7. formation of first neutron stars

Match different properties with the appropriate objects (Note: the same option can be used more than once). Pulsar, Quasar, both, or neither: 1. They involve a compact object. 2. They emit large amounts of high-energy radiation (X-rays). 3. Their luminosity is larger than the luminosity of all combined stars of a galaxy. 4. Their emission varies on regular periods

1. both quasars and pulsars 2. quasars 3. quasars 4. pulsars

The Hubble relationship, that relates speed of galaxies (V) and their distance from the Milky Way (D), is V = H x D where H is a constant. What distance would this relationship predict for a galaxy that is moving at 700 km/s speed, if the Hubble constant (H) is assumed to be 70 km/s/Mpc?

10 megaparsecs

A star is composed of 71% hydrogen and 27% helium. The metallicity (percentage of heavier elements) of that star is

2%

The diagram below illustrates the velocities of galaxies for a model of expanding universe with H0= 50 km/s/Mpc as seen from the Milky Way. What would be the velocity of Galaxy #4 with respect to Galaxy #2?

500 km/s

which of these plots best illustrates the star formation rate for an elliptical galaxy?

A

What property determine if the universe will expand forever?

A/B/C A. the amount of normal matter in the universe B. the amount of dark matter in the universe C.the amount of dark energy in the universe

Which of the items marked on the image of the golden record was designed to help another civilization figure out where the message came from?

B

which of these graphs correctly reflects the relationship between recessional velocity Vr and distance D for galaxies as expressed by Hubbles law?

B

Harlow Shapley estimated the location of the center of the Milky Way by assuming it was the center of the distribution of globular clusters. Based on the figure below the center is located at the position

C

T/F All galaxies are moving away from the Milky Way with the nearest galaxies moving fastest.

False

The pictures below show three possible geometries of the universe, which depend on the density of matter and energy of the whole universe with respect to a critical value. Order them from the lowest to the highest density.

Fig. C Fig. B Fig. A

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

She should measure the speed of stars or gas near the outer regions of the galaxy.

Among irregular galaxies what makes the Large and Small Magellanic Clouds especially useful for astronomers?

They are (for galaxies) very close to us, so they are easy to study.

Match each picture with the appropriate process.

a) This process leads to the emission or absorption of a radio line with wavelength of 21 cm b) Interaction of visible light with interstellar dust that causes the reddening of the source c) Microscopic structure of an interstellar dust grain

Extremophiles that might thrive in this river in Spain are called

acidophiles

A spiral galaxy consists of

both a disk and spheroidal component

Earth's early atmosphere probably was made up mostly of

carbon dioxide

Which of the following galaxies is the Milky Way?

e) none of the above

The galaxy at the center of a well-populated cluster of galaxies is most likely a(n) ...

elliptical galaxy

The images above show stromatolites which are important in understanding

evolution of living creatures during the early history of Earth

What does fc stand for in the Drake equation?

fraction of planets that developed communicating civilizations

A protogalactic cloud that forms an elliptical galaxy would likely have

high density and small angular momentum

The Hubble's diagram below illustrates the uncertainties for a few galaxies. The uncertainties on the galaxy distances are due to difficulties encountered applying different techniques of distance determination. Based on the plot we can conclude that these uncertainties

increase with distance

According to the Cosmological Principle, the universe

is isotropic and homogeneous

Astrobiologists were excited by this picture of a moon of Saturn because

it shows plumes of ice and gas that may indicate liquid water beneath the icy surface

Galaxy collisions were ... in the early universe than they are today.

more common

An irregular galaxy consists of

neither a disk or spheroidal component

Extragalactic astronomy is often compared to a time machine because ...

observing different galaxies at different distances is equivalent to looking at different cosmic times, which allows one to study the evolution of galaxies.

Two "biomarkers", that if found together might be a strong signal for life on an exoplanet, are _______________ and ___________________.

oxygen, methane

What method was originally used in 1920 to determine the distance of "nebulae"?

pulsating variables method

Today we know that what all quasars have in common is that they appear to be small sources of energy with

redshifts that indicate they are far away

Spiral galaxies appear white because they contain

stars of all ages and colors

The Hubble tuning fork is useful for

summarizing galaxy classification by morphology

The Hubble tuning fork is useful for ...

summarizing galaxy classification by morphology

The idea that there is nothing special about our place in the universe is sometimes referred to as

the Copernican principle

Scientists speculate that the properties (laws) of the universe must be the way they are because if they were significantly different, we would not be here to think about them. This idea is called

the anthropic principle

When two galaxies collide why don't their stars typically collide?

the distance between stars is very large compared to their size

This image shows the expected and observed rotation curves for a galaxy. The fact that the observed speed of stars is much faster than expect near the far edge of the galaxy is an indicator that

the galaxy includes mysterious "dark matter"

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

The "habitable zone" for a planet orbiting a star is

the region in which water can exist as a liquid on the surface of the planet

The two figures below represent

the same region of the sky; Fig. A in the infrared and Fig. B in the visible band.

Because of the expansion of the universe, which of these objects are moving apart?

two widely separated galaxies

Which of the following objects i s considered useful to astronomers as a "standard bulb" (also called "standard candle") for determining distances.?

type Ia supernovae