ISP 205 - Visions of the Universe Exam 3

What is happening inside a main sequence star?

Hydrogen is fusing to make helium in the core.

Which of the following objects never was a star?

a brown dwarf

How is the lifetime of a star related to its mass?

More massive stars live much shorter lives than less massive stars.

What will Betelgeuse, a red supergiant star, eventually end up as?

a supernova

What happens to the core of a star after the core has been converted from hydrogen to helium?

It shrinks and heats.

What can prevent a star core from making heavy elements (atomic number greater than 2)?

Electron degeneracy pressure prevents any further shrinking.

What produces most of the oxygen in the universe?

high mass stars

Which type of pressure balances gravity in a main sequence star like the Sun?

Gas pressure

Why does a red giant star's luminosity slowly increase with time?

The rate of the fusion reactions in a shell of hydrogen is slowly increasing.

Which star can produce the elements with the most protons in their nuclei?

The most massive star

How will our Sun die or end up as?

As a white dwarf

What did scientists NOT learn from the direct detection of gravitational waves by the LIGO project from the merger of two black holes? (Be sure to choose the answer describing what they did NOT learn. Read all the choices before making your selection.)

IncorrectGravitational waves are directly detectable.
IncorrectBlack holes of around 30-40 solar masses each exist.
IncorrectBlack hole mergers happen.
Correct:Einstein's theory was wrong.

Which of the following events require mass transfer from a companion in order to occur?

Nova, white dwarf supernova

How can we estimate the mass of an otherwise invisible compact object?

By measuring the speed and period of the orbital motion of its companion star.

What rare element appears to be among those created when two neutron stars merge?

Gold

Why did the discovery of pulsars provide strong evidence for the existence of neutron stars?

White dwarfs, stars, and planets cannot spin that quickly without breaking apart.

Which of the following compact objects, each in a binary system with its own O-star companion, is potentially a black hole because it can't be anything else? The binary system with the ...

4 solar mass compact object

Which of the following compact objects, each in a binary with an O-star companion, possibly contains a white dwarf? The binary system with the ...

Correct:1 solar mass compact object.
Incorrect2 solar mass compact object.
Incorrect4 solar mass compact object.

What happens when a white dwarf increases in mass?

It gets smaller in radius

What happens to black hole's event horizon when a black hole increases in mass?

It gets bigger.

Which star is more likely to be a star younger than the Sun?

Disk star

In a simple model for how the galaxy formed, which stars formed first?

Halo stars

In a simple model for how the galaxy formed, why are disk stars in the disk?

They formed from clouds within a galaxy-sized rotating disk of gas.

How do scientists know there is a 4-million solar mass black hole in the center of our own Galaxy?

By watching stars orbit an invisible object in the center of the Galaxy, they infer its mass and its location.

What types of orbits are associated with the halo and the disk of our galaxy?

Halo: Random directions, Disk: Same direction, same plane.

Which of the following initial conditions in a proto-galactic gas cloud would be more likely to lead to the formation of an elliptical galaxy?

Rapid, early star formation.

Which type of galaxy is usually more luminous and more reddish in color?

Ellipticals

Which observation would support the hypothesis that all of the stars in a single galaxy are born at one time?

All of the stars in that galaxy are very old.

Put the chain of methods used to determine distance in order, from methods used for the nearest distances first.

Radar, parallax, white dwarf supernova

Which type of galaxy is most like the Milky Way Galaxy?

Spirals

Which type of galaxy is best characterized by having a prominent disk?

Spirals

Which type of star is an important standard candle for distance determination?

Cepheid Variable

You have determined that the maximum apparent brightness of a white dwarf supernova in the Coma Galaxy is a factor of nine times fainter than the maximum apparent brightness of a white dwarf supernova happening in the Virgo Galaxy. How much farther away is the Coma Galaxy than the Virgo Galaxy?

3 times as far

Consider an H-R diagram for observations of all of the stars in a single star cluster. Which are the largest stars, by size of their radii?

the highest luminosity, coolest stars

What is the escape velocity one meter inside a black hole's event horizon? (By "inside" we mean closer to the center of the black hole than the event horizon is.)

Greater than the speed of light

Which type of pressure balances gravity in a white dwarf?

electron degeneracy pressure

Ming measures a recession velocity of 1000 km/sec for a galaxy. About how far away is that galaxy if the Hubble constant is 20 km/sec/million light years? (Hint: be sure to check the units in your calculation.)

50 million light years. (1000/20)

If astronomer Terry thinks Hubble's constant is 20 km/s/million light-years and astronomer Chris thinks that Hubble's constant is 25 km/s/million light-years, all other things being equal (they agree on other aspects of the Universe): which astronomer thinks the universe is younger?

Chris (one moving faster is younger)

Assume all galaxies are "born" (or make their first stars) within about a billion years after the Big Bang. Which galaxy, as we observe it through a telescope, do we observe in its older stage of life? Stop and think this one through carefully: work it out for yourself before answering.

A galaxy at a distance of 10 million light-years.

Which of the following environmental conditions appears to be more favorable to making an elliptical galaxy?

Densely populated, lots of other galaxies around.

What is the third most abundant element in the universe?

oxygen

Consider an object in orbit around a star. The star suddenly shrinks in size, but does not change its mass. What happens to the object's orbit?

it remains in the same orbit

Identify the correct sequence of life events for a high mass star

main sequence, red supergiant, supernova, neutron star

Which of the following properties describes a low-mass star?

Has longer lifetimes than high mass stars.

How are the ages of stars in the Milky Way related to their orbits? Choose the best answer.

The halo has mostly old stars; both young and old stars are in the disk.

If the Sun somehow acquired more hydrogen and helium and doubled in mass, what would happen to it?

it would evolve more quickly than it is now

Which stars are more common?

white dwarfs

Order the following objects in increasing size (radius):

neutron star, white dwarf, Jupiter, Sun

Why would life (as we know it) not exist if stars were somehow evenly sprinkled through the universe, not clustered into galaxies?

Recycling of gas through generations of stars would not happen.