Question 1

A visual binary system has an observed period of 5 years and a semi-major axis of 10 AU.What is the sum of the masses of the two stars?&#10;A)10 solar masses&#10;B)5 solar masses&#10;C)100 solar masses&#10;D)40 solar masses

Accepted Answer

We can use Kepler's third law to relate the period and semi-major axis of the binary system to the sum of the masses:
P^2 = (4π^2/G) (a^3 / (M1 + M2))
where P is the period in years, a is the semi-major axis in AU, G is the gravitational constant, M1 and M2 are the masses of the two stars in solar masses.

We can rearrange this equation to solve for the sum of the masses:
M1 + M2 = (4π^2/G) (a^3 / P^2)

Plugging in the given values, we get:
M1 + M2 = (4π^2/6.674×10−11 m^3 kg−1 s−2) ((10 AU * 1.496×10^11 m/AU)^3 / (5 years)^2) * (1 solar mass / 1.989×10^30 kg)
M1 + M2 = 39.73 solar masses

Rounding the answer to the nearest whole number, we get 40 solar masses.

Question 2

A light curve is a plot showing&#10;A)Luminosity versus spectral type&#10;B)Brightness versus time&#10;C)Radial velocity versus magnitude&#10;D)Mass versus luminosity

Accepted Answer

A light curve is a plot that shows the variation in brightness of an object over time. It is often used in astronomy to track the changes in brightness of stars, variable stars, and other celestial objects.

Question 3

Which type of binary star is revealed by changes in the relative directions to the two stars?&#10;A)Spectroscopic binaries&#10;B)Eclipsing binaries&#10;C)Visual binaries&#10;D)Common envelope binaries

Accepted Answer

Visual binaries are revealed by changes in the relative directions between the two stars. This means that the stars can be seen as separate points of light and observed to move around each other over time. In contrast, spectroscopic binaries are detected through variations in the Doppler shift of spectral lines, while eclipsing binaries are identified by periodic drops in brightness when one star passes in front of the other. Common envelope binaries involve two stars in a shared envelope of gas and are not typically characterized by changes in direction.

Question 4

Our determination of stellar masses comes from&#10;A)Observations of binary stars&#10;B)The mass luminosity relation&#10;C)Measurement of stellar colors and use of blackbody radiation&#10;D)Precise measurements of the diameters of stars

Accepted Answer

Observations of binary stars allow us to determine the masses of the stars by measuring their orbital velocities and periods. By applying Kepler's laws, we can then calculate the masses of the stars. This method is one of the most accurate ways to determine stellar masses.

Question 5

What information about a binary star system is needed in order to calculate the sum of the masses of the two stars?&#10;A)Orbital period and separation&#10;B)Distance and spectral type&#10;C)Age and temperature&#10;D)Magnetic field and rotation period

Accepted Answer

The sum of masses of the two stars in a binary system can be calculated using Kepler's third law which involves the orbital period and separation between the two stars. Knowing the distance and spectral type, age and temperature or magnetic field and rotation period does not provide sufficient information to calculate the sum of masses of the two stars.

Question 6

If the mass-losing star in a close binary system is the more massive star,the binary will&#10;A)Decrease its separation&#10;B)Undergo a period of very slow mass exchange&#10;C)Immediately experience a supernova eruption&#10;D)Change the orbital plane of the two stars

Accepted Answer

In close binary systems, the gravitational interaction between the two stars can cause them to transfer mass. If the more massive star is also the one losing mass, then the loss of mass will cause the gravitational pull between the two stars to increase, resulting in a decrease in their separation distance. This process can continue until the stars merge or until some other stabilizing mechanism kicks in. Therefore, the binary will decrease its separation if the mass-losing star is the more massive one.

Question 7

The explosive burning of hydrogen on the surface of a white dwarf produces a&#10;A)Supernova&#10;B)Nova&#10;C)Pulsar&#10;D)Splitting of the white dwarf into a binary system

Accepted Answer

The explosive burning of hydrogen on the surface of a white dwarf results in a nova. A nova is a type of transient astronomical event that occurs in binary systems where one component is a white dwarf. The white dwarf accretes hydrogen from its companion star and once a critical temperature and density is reached, a thermonuclear explosion occurs on the surface of the white dwarf, leading to a sudden brightening of the system. This explosion ejects the outer layers of the white dwarf into space, creating a shell of gas around it, which can expand and cool over several years. Unlike a supernova, a nova does not destroy the white dwarf, which can continue to accrete material and possibly undergo additional nova eruptions in the future.

Question 8

What property of a star can almost never be determined unless it is a member of a binary star system?&#10;A)Distance&#10;B)Luminosity&#10;C)Mass&#10;D)Chemical composition

Accepted Answer

Mass is the property of a star that can almost never be determined unless it is a member of a binary star system. This is because there are different methods to measure other properties of a star like distance, luminosity, and chemical composition, but measuring mass requires observing the gravitational interaction between two stars in a binary system.

Question 9

Under what conditions is it possible for a white dwarf star to produce a nova outburst?&#10;A)If the white dwarf is rotating rapidly&#10;B)If the white dwarf completely evaporates,producing gamma rays&#10;C)If the white dwarf accretes matter from a binary companion&#10;D)If the white dwarf collides with another star

Accepted Answer

A white dwarf can produce a nova outburst if it accretes matter from a binary companion. This matter accumulates on the surface of the white dwarf, causing a thermonuclear explosion and a sudden increase in brightness. Rapid rotation or collisions with other stars are not necessary conditions for a nova outburst to occur. Complete evaporation of the white dwarf would result in a different type of event called a gamma-ray burst, not a nova.

Question 10

A type Ia supernova is caused by&#10;A)The abrupt consumption of carbon in a white dwarf&#10;B)The expulsion of the accretion disk of a neutron star&#10;C)A black hole pulling its binary companion through its event horizon&#10;D)The collapse of the core of a neutron star in a binary system

Accepted Answer

A type Ia supernova occurs when a carbon-oxygen white dwarf, which is a remnant of a formerly low-mass main-sequence star, accretes matter from a companion star until it reaches a critical mass limit (known as the Chandrasekhar limit), causing a runaway fusion reaction that completely disrupts the white dwarf and releases a large amount of energy and material into space. This process is known as a thermonuclear supernova.

Question 11

What percentage of stars are members of binary or multiple star systems?&#10;A)1%&#10;B)10%&#10;C)50%&#10;D)99%

Accepted Answer

The answer of What percentage of stars are members of...

Question 12

L1 refers to&#10;A)The spectral type of the fainter star in a binary system&#10;B)The point through which gas flows from one star to the other&#10;C)The orbital period of an eclipsing binary&#10;D)The distance between the two stars in AU

Accepted Answer

The answer of L1 refers to&#10;A)The spectral type of the...

Question 13

A nova is produced by an explosion on the surface of a&#10;A)Supergiant&#10;B)White dwarf&#10;C)Main sequence star&#10;D)Black hole

Accepted Answer

The answer of A nova is produced by an explosion...

Question 14

What kind of objects are thought to be identified with flickering X-ray sources?&#10;A)Binary star systems containing black holes&#10;B)Supernova remnants like the Crab Nebula&#10;C)Pre-main sequence stars&#10;D)Main sequence stars on which flares occur

Accepted Answer

The answer of What kind of objects are thought to...

Question 15

Gas shed by the companion of a neutron star or black hole normally&#10;A)Flows out of the binary system&#10;B)Falls directly onto the neutron star or black hole&#10;C)Flows into an accretion disk&#10;D)Collects above the poles of the neutron star or black hole

Accepted Answer

The answer of Gas shed by the companion of a...

Question 16

When a black hole is part of a close binary star system,the system may be a strong source of X-rays.Where do the X-rays come from?&#10;A)The companion star,which is heated by the black hole&#10;B)A disk of hot matter around the black hole&#10;C)From the black hole itself&#10;D)From planets that are captured by the black hole

Accepted Answer

The answer of When a black hole is part of...

Question 17

Mass exchange in close binary systems can produce&#10;A)X-ray emission from an accretion disk&#10;B)The formation of planets&#10;C)T-Tauri stars&#10;D)Dark markings like sunspots

Accepted Answer

The answer of Mass exchange in close binary systems can...

Question 18

A nova is produced by an explosion that ___________ .&#10;A)only happens once,and results in the destruction of the white dwarf.&#10;B)can happen many times,and does not destroy the white dwarf.&#10;C)can only happen when the iron core collapses.&#10;D)is the end state of a star with eight times the mass of our Sun.

Accepted Answer

The answer of A nova is produced by an explosion...

Question 19

A star that is discovered to be a binary system on the basis of the variations in its brightness is called a(n)&#10;A)Spectroscopic binary&#10;B)Astrometric binary&#10;C)Visual binary&#10;D)Eclipsing binary

Accepted Answer

The answer of A star that is discovered to be...

Question 20

A pulsar will be produced if a neutron star is___________ .&#10;A)in isolation,with no binary star companion.&#10;B)in the proximity of an evaporating binary companion.&#10;C)formed,regardless of the external conditions.&#10;D)more than one of the above

Accepted Answer

The answer of A pulsar will be produced if a...

Deck 21: Binary Star Systems