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What is believed to be the maximum mass for a neutron star?

3 solar masses

What is the Schwarzschild radius of a 2-solar-mass black hole?

6 km

If a type II Cepheids variable star has a period of 10 days with a visual magnitude of 2, determine the distance to this variable star using the plot in figure-1.

63 pc

Approximately how far is the Sun from the center of our galaxy?

8 kpc

One object that is believed to be a black hole in our galaxy is

Cygnus X-1, a powerful X-ray source.

Why are we able to see only a small part of our galaxy, the Milky Way galaxy?

Distant stars are obscured by dust in interstellar space.

The existence of stars composed almost entirely of neutrons was first predicted by

Fritz Zwicky and Walter Baade, in 1933

What prevents a neutron star from collapsing and becoming a black hole?

Gravity in the neutron star is balanced by an outward force due to neutron degeneracy

The period-luminosity relationship for Cepheid variable stars, relating variability to absolute overall brightness, thereby providing identifiable beacons throughout our local space, was discovered by

Henrietta Leavitt

In 1785 William Herschelproposed that the solar system was at the center of the Milky Way galaxy. How did he reach this conclusion?

Herscel's observations suggested that the stars in the Milky Way galaxy were distributed uniformly around Earth

. What do we know about the geometry of the dark matter distribution in the vicinity of the Milky Way galaxy?

It appears to be a spherical halo.

What is the significance of the object Sagittarius A* ("Sagittarius A-star") in our galaxy?

It appears to be the actual nucleus of the galaxy.

What is the likely final fate of a star that has a mass of 15 solar masses after completing its nuclear fusion burning phases?

It collapses and becomes a black hole.

What would happen to the gravitational force on Earth if the Sun were to be replaced by a 1-solar-mass black hole?

It would remain as it is now.

The milky way is an example of which type of galaxy?

Spiral

Observation of the different components of the Milky Way galaxy indicates that the spiral arms contain very different populations of stars and other material from those in globular clusters. In what way are they different?

Spiral arms contain young stars, dust and gas within which star formation continues, whereas globular clusters contain older star populations, with no dust and gas and no on-going star formation.

What happens to the Schwarzschild radius of a black hole if you double its mass?

The Schwarzschild radius is doubled.

At first it was thought that nothing could ever escape from a black hole, yet astronomers are now locating black hole candidates by the X-rays they emit. Do they really see X- rays coming from a black hole?

The X-rays come from highly compressed matter in the accretion disk outside the event horizon of the black hole.

Which of the following statements correctly describes the rotation of our galaxy?

The disk rotates differentially (objects further from the center take longer to complete an orbit than objects closer to the center), and the halo objects have random orbits with no net rotation of the halo about the center of the galaxy.

. How does the diameter of a black hole (size of the event horizon) depend on the mass inside the black hole?

The greater the mass, the greater the diameter.

We aim our radio telescope at a distant region of our galaxy and detect 21-cm radio waves with no Doppler shift. Each of the following is a possible explanation except one. Which is the exception?

The neutral hydrogen in this region is moving away from us instead of toward us.

Suppose that a neutron star of 2.8 solar masses is part of a binary star system in which the other star is a normal giant star. What would happen if half a solar mass of material were transferred onto the neutron star from its companion?

The neutron star would collapse and become a black hole.

A binary system is formed with a neutron star and another star which has overflowed its Roche lobe. How does the detection of such a binary differ from the detection of an isolated neutron star?

This binary may emit intense X-rays while an isolated neutron star emits radio waves.

Neutron stars are believed to be created primarily by

Type II supernovae (explosions in high mass stars).

Is there a relationship between the age of a normal pulsar (i.e., not a millisecond pulsar) and its rotation rate?

Yes. The slower they spin the older they are

Which of the following components of the galaxy best outline the spiral arms of the galaxy?

Young O and B stars, dust and gas

In a binary star system, an unseen component is found to have a mass of about 8 solar masses. If this were a normal star, then it would be visible, so it must be a collapsed object. Theoretical considerations tell us that it must be

a black hole

A mass of about 2 solar masses is imploded inward by a supernova explosion. What is the result of this implosion?

a neutron star, its size governed by neutron degeneracy pressure

What is a singularity?

a point of infinite density

What is a pulsar?

a rapidly rotating neutron star, producing beams of radio energy and in some cases, light and X-rays

What type of object has been proposed to explain the tremendous activity detected at the center of our galaxy?

a supermassive black hole

What is the upper limit to the mass of a neutron star beyond which neutron degeneracy pressure is unable to withstand the force of gravity and the neutron star is crushed out of existence into a black hole?

about 3 solar masses

A neutron star will be detected from Earth as a pulsar by its regular radio pulses only if the Earth lies

almost directly in line with the magnetic axis of the neutron star at some time during the star's rotation

The interior of a neutron star is believed to consist of

almost entirely neutrons, but with some protons and electrons.

The first pulsar was discovered by

an English graduate student, Jocelyn Bell, in 1967

. A map of our galaxy deduced from radio observations of the 21-cm line emission from cool hydrogen gas reveals

at least four spiral arms and several short arm segments.

At what location in the space around a black hole does the escape velocity become equal to the speed of light?

at the event horizon

The pressure within a neutron star that opposes the inward force of gravity comes from

both degenerate neutron pressure and the repulsive hard core aspect of the nuclear force between neutrons.

How is the mass of the galaxy estimated?

by applying Newton's extension of Kepler's laws to the motion of the Sun and other stars

Synchrotron radiation is emitted whenever

charged particles are forced to move along curved paths within a magnetic field.

Variable stars, such as Cepheid variables and RR Lyrae stars, are used in what important measurement in astronomy?

distance measurement

The intense X-rays emitted by a suspected black hole are generated by what physical mechanism?

frictional and compressional heating as material moves into the hole

Where in space would you look for a globular cluster?

in the Milky Way halo, orbiting the galactic center in a long elliptical orbit

In our galaxy, young metal-rich stars are found

in the disk and spiral arms.

Where is the solar system located in our galaxy?

in the galactic disk

The periods of most pulsars

increase with time

Much of the mass of our galaxy appears to be in the form of "dark matter" of unknown composition. At present this matter can be detected only because

its gravitational pull affects orbital motions of matter in the galaxy

The 21 centimeter line is one of the most important wavelengths in radio astronomy. That it is a relatively long wavelength is important because

long wavelengths are more likely to pass through clouds of gas and dust

The mechanism that gives rise to the phenomenon of the nova is

matter from a companion star falling onto a white dwarf in a close binary system, eventually causing a nuclear explosion on the dwarf's surface

Recent observations suggest that the Milky Way

may have a central bar, formed by an elongation of the central bulge.

The stars in the Milky Way galaxy

move generally around the galactic center

The 21 centimeter line is one of the most important wavelengths in radio astronomy. It is produced mainly in

neutral hydrogen

Which of the following astronomical objects are most closely associated with pulsars?

neutron stars

Pulsating X-ray sources are believed to be

neutron stars in binary systems, emitting X-rays because of mass transfer onto the neutron star from its normal companion.

Black holes are named so because

no light or any other electromagnetic radiation can escape from inside them

What is actually located at the event horizon of a black hole, to define this entity?

nothing

The disk of the Milky Way appears bluish because of the light from the many O and B type stars found there. What color tint would you expect globular clusters to take on?

red

The Crab Nebula is a nearby example of what type of physical phenomenon?

remnant of a supernova explosion

When distances were carefully measured from Earth to globular clusters above and below the Milky Way plane (where our view of them is not obscured by interstellar dust and gas), their distribution was found to be

spherically symmetric about a point in the constellation Sagittarius and concentrated in that direction

According to the density-wave theory of spiral structure in galaxies

stars and interstellar clouds spend more time in regions of higher density, thus maintaining the higher density of the region

Glitches are occasionally observed by astronomers studying pulsars. What are these glitches?

sudden increases in rotation rate

The diameter of a typical neutron star of 1 solar mass is predicted to be approximately

that of an average city, about 30 km.

What is the event horizon of a black hole?

the "surface" from the inside of which nothing can escape

Where in the Milky Way would you expect most star formation to be taking place?

the disk and spiral arms

The Schwarzschild radius of a black hole is the distance from the singularity (center) to

the event horizon, from which light cannot escape

Astronomers have found the existence of spiral arms in galaxies difficult to account for because

the inner part of a galaxy rotates in a shorter time than the outer parts, so the arms should have wound up so tightly that they would have disappeared over the lifetime of the galaxy.

The method used by Harlow Shapley in 1917 to estimate the Sun's location in our galaxy was the measurement of

the locations of globular clusters around the galaxy

The pulsed nature of the radiation at all wavelengths that is seen to come from a pulsar is produced by

the rapid rotation of a neutron star that is producing two oppositely directed beams of radiation.

. The possible presence of a very large amount of unseen ("dark") matter in the halo of our galaxy is deduced from

the rotation curve of our galaxy, which indicates higher than expected orbital speeds in the outer regions of the galaxy.

What evidence now exists for a supermassive black hole at the center of our galaxy?

very rapid motion of matter close to the nucleus of the galaxy, requiring a very massive body to hold it in orbit

The fastest pulsars, called millisecond pulsars, have periods of about 1/1000 second. The reason they pulse so much faster than (for example) the Crab and Vela pulsars is that they

were spun up by mass transferred on to them from a companion in a binary star system.

Which is the correct sequence for the following end-points of stellar evolution, in order of increasing maximum mass?

white dwarf, neutron star, black hole