Astronomy Test 3

Procyon lies about 13 light years distant, thus its parallax is about: A) 0.25" B) 0.40" C) 1.3" D) 0.01" E) 0.65"

A) 0.25"

What temperature is needed to fuse helium into carbon? A) 100 million K B) 100,000 K C) 15 million K D) one billion K E) 5,800 K

A) 100 million K

What effect does dust have on visible light passing through it? A) It dims and reddens it. B) It completely blocks all visible light from passing through. C) It ionizes the light and creates emission lines. D) All light is turned bluish in color. E) It makes the light coming from stars appear to twinkle

A) It dims and reddens it.

What makes the Crab pulsar somewhat unusual among pulsars in general? A) It is rather bright at visible wavelengths. B) It is the oldest pulsar observed. C) It is the fastest pulsar known. D) Its period is not regular like other pulsars. E) It is the most intense source of X-rays in the sky.

A) It is rather bright at visible wavelengths.

Why couldn't you stand on the Sun's surface? A) The Sun doesn't have a solid surface. B) You could stand on it, if a sufficiently protective spacesuit could be designed. C) You could stand on the surface. D) The Sun's surface is too highly magnetized for anything to survive there. E) The Sun has no surface at all...the photosphere is an illusion.

A) The Sun doesn't have a solid surface.

What is it about the Sun's corona that astronomers don't understand? A) The corona is much hotter than layers of the Sun that are closer to the solar interior. B) The corona seems to absorb 2/3 of the neutrinos that pass thorough it. C) The Sun's corona extends to the outer reaches of the solar system. D) During total solar eclipses, the corona sometimes disappears from view. E) No one knows why that part of the Sun's atmosphere does not drift away into space.

A) The corona is much hotter than layers of the Sun that are closer to the solar interior.

5. The Sun will get brighter in the next 4 to 5 billion years. A) True B) False

A) True

As a protostar evolves from stage 4 to stage 6, it gets hotter but much less bright. A) True B) False

A) True

As a star begins to evolve away from the main sequence, it gets larger. A) True B) False

A) True

Brown dwarfs are failed stars, never igniting their hydrogen fusion. A) True B) False

A) True

Dark dust clouds radiate mainly in the radio portion of the electromagnetic spectrum. A) True B) False

A) True

Hydrogen is the major gas in the interstellar medium. A) True B) False

A) True

In a white dwarf, the density of a million times that of normal matter is achieved by the crushing of the electron orbitals around the nucleus. A) True B) False

A) True

In the proton-proton chain, two neutrinos are created for every helium. A) True B) False

A) True

In the proton-proton cycle, you must first make deuterium, then helium. A) True B) False

A) True

Neutron stars are the products of only type II supernovae. A) True B) False

A) True

Stars between 8 and 25 solar masses will produce neutron stars when they collapse. A) True B) False

A) True

Stars of less than 8 solar masses will produce white dwarfs when their cores collapse. A) True B) False

A) True

The Sun is a fairly normal star. A) True B) False

A) True

The birth of stars is a battle between gravity and radiation pressure. A) True B) False

A) True

The density of a neutron star is comparable to the density of an atomic nucleus. A) True B) False

A) True

The nearest star to our Sun, Alpha Centauri, is still over a parsec distant. A) True B) False

A) True

The positron is in fact an anti-electron. A) True B) False

A) True

The surface temperature of the photosphere is about 5,800 K. A) True B) False

A) True

While the Sun's volume is over a million earths, it is not as dense as the Earth. A) True B) False

A) True

What information does 21-centimeter radiation provide about the gas cloud that emitted it? A) all of the above B) none of the above C) temperature D) density E) radial velocity

A) all of the above

By what mechanism does solar energy reach the Sun's photosphere from the layer just underneath it? A) convection B) conduction C) ionization D) differentiation E) radiation

A) convection

What are the two most important intrinsic properties used to classify stars? A) luminosity and surface temperature B) distance and surface temperature C) distance and color D) mass and age E) distance and luminosity

A) luminosity and surface temperature

For gravity to contract a spinning interstellar cloud, there needs to be sufficient: A) mass and density. B) rotation. C) charged ions. D) magnetism. E) heat.

A) mass and density.

The "helium flash" occurs at what stage in stellar evolution? A) red giant B) when the T Tauri bipolar jets shoot out C) in the middle of the main sequence stage D) planetary nebula E) horizontal branch

A) red giant

What is the significance of 100 million K to the core of a star? A) temperature need to start triple alpha process and turn helium into carbon B) temperature needed to fuse carbon into oxygen C) temperature needed to fuse iron and create a type II supernova D) temperature needed to fuse deuterium for brown dwarfs E) temperature to fuse hydrogen into helium in the proton-proton cycle

A) temperature need to start triple alpha process and turn helium into carbon

What is the absolute magnitude of our Sun? A) +9.4 B) +4.8 C) -1.4 D) -23.0 E) -4.6

B) +4.8

Neutral hydrogen is most obvious in the E-M spectrum at: A) has yet to be detected in space. B) 21 cm in the radio region. C) 656.3 nm, hydrogen alpha red. D) in yellow light of the Sun's continuum. E) 121.3 nm, the Lyman alpha ultraviolet line.

B) 21 cm in the radio region.

Who received the Nobel Prize in Physics for relating pulsars to neutron star formation? A) Martin Schwarzschild B) Anthony Hewish C) Stephen Hawking D) Sir Bernard Lovell E) Jocelyn Bell

B) Anthony Hewish

All neutron stars are pulsars, but not all pulsars are neutron stars. A) True B) False

B) False

Collisions between galaxies tend to destroy, not create, stars. A) True B) False

B) False

Like most pulsars, the Crab Nebula neutron star is known only by its radio pulses. A) True B) False

B) False

Newly formed neutron stars have weak magnetic fields which strengthen over time, due to the conservation of angular momentum. A) True B) False

B) False

Star A and star B have the same apparent magnitude. Star A is twice as distant as star B. Therefore, star A has twice the luminosity as star B. A) True B) False

B) False

The "solar constant" refers to the observation that the Sun's brightness does not ever change. A) True B) False

B) False

Perhaps the greatest of the Greek astronomers, ________ compiled the first catalog of stars, accurately measured their positions, and defined the basic system of stellar brightnesses. A) Aristarchus B) Hipparchus C) Ptolemy D) Erastothenes E) Aristotle

B) Hipparchus

The density of the Sun is similar to which object? A) Halley's Comet's nucleus B) Jupiter C) the Moon D) Mercury E) the Earth

B) Jupiter

Which of the following is NOT a property of neutrinos? A) almost massless B) cannot interact at all with normal matter C) can travel very close to the speed of light D) can change forms in the eight minutes from the Sun's core to us E) neutral in charge

B) cannot interact at all with normal matter

The numbers of sunspots and their activity peak about every: A) 36 days. B) eleven years. C) six months. D) year. E) 76 years.

B) eleven years.

How long does it take for a star like our Sun to form? A) one billion years B) fifty million years C) 100 thousand years D) 4.6 billion years E) two million years

B) fifty million years

A high-mass star dies more violently than a low-mass star because: A) it cannot fuse elements heavier than carbon. B) it generates more heat and its core eventually collapses very suddenly. C) gravity is weakened by its high luminosity. D) it must always end up as a black hole. E) it is most often found as part of a binary system.

B) it generates more heat and its core eventually collapses very suddenly.

The most common molecule in a molecular cloud is: A) carbon monoxide, CO. B) molecular hydrogen, H2. C) water, H2O. D) methane, CH4. E) ammonia, NH3.

B) molecular hydrogen, H2.

Which is the strongest of the fundamental forces? A) gravity B) strong nuclear force C) dark energy D) electromagnetism E) weak nuclear force

B) strong nuclear force

The key to identifying a black hole candidate in a binary system is that: A) the visible companion must be an evolving main sequence or giant star. B) the unseen companion in the system must have a sufficiently high mass. C) the unseen star is a contact binary. D) one of the two stars cannot be seen. E) the system must be a very strong source of radio emissions.

B) the unseen companion in the system must have a sufficiently high mass.

Which of the following best describes the size and distance relationship of our Sun and the nearest star? A) a tennis ball here, another on the Moon B) two golf balls separated by 100 kilometers C) two beach balls separated by 100 city blocks D) two baseballs separated by 100 yards E) two grains of sand separated by 100 light years

B) two golf balls separated by 100 kilometers

The order of evolutionary stages of a star like the Sun would be Main Sequence, giant, planetary nebula, and finally: A) neutron star. B) white dwarf. C) nova. D) hypernova. E) black hole.

B) white dwarf.

If a star is found by spectroscopic observations to be about 500 parsecs distant, its parallax is: A) .5" B) .005" C) .002" D) .2" E) .02"

C) .002"

How many hydrogen atoms does it take to make a typical star? A) 10^18 B) 10^10 C) 10^57 D) 10^6 E) 10^25

C) 10^57

If a star has a parallax of 0.05", then its distance in light years is about: A) 100 light years. B) 6.4 light years. C) 65 light years. D) 12.7 light years. E) 20 light years.

C) 65 light years.

Which statement is true, in terms of stellar evolution? A) Gravity lets up under certain circumstances. B) There are no discernable trends here. C) Sooner or later, gravity wins. D) Sometimes gravity wins and sometimes gravity loses. E) Sooner or later, gravity loses.

C) Sooner or later, gravity wins.

What is the meaning of the "solar constant"? A) The regularity of the sunspot cycle has not changed since Galileo. B) Like Venus, the surface appearance of the Sun is featureless. C) The solar energy reaching Earth per unit area per unit time. D) The Sun's position in the Milky Way is central and immobile. E) The size of the Sun never changes.

C) The solar energy reaching Earth per unit area per unit time.

A star spends most of its life: A) as a red giant or supergiant. B) as a T Tauri variable star. C) as a main sequence star. D) as a protostar. E) as a planetary nebula.

C) as a main sequence star.

Some regions of the Milky Way's disk appear dark because: A) there are numerous black holes there that capture all the star light behind them. B) stars in that direction are obscured by interstellar gas. C) stars in that direction are obscured by interstellar dust. D) there are no stars there. E) the magnetic field has directed the polarized light away from these regions.

C) stars in that direction are obscured by interstellar dust.

What is the critical temperature at which hydrogen can fuse into helium in the star's core? A) 5,800 K B) 26,000 K C) ten million K D) one million K E) 100 million K

C) ten million K

Which of the following apparent magnitudes is the brightest? A) +4.8 B) -1.4 C) +25.7 D) -23 E) +9.2

D) -23

What is the average temperature of interstellar gas and dust? A) 0 K B) 1,000 K C) 2.73 K D) 100 K E) 5,800 K

D) 100 K

The temperature of the layer of gas that produces the visible light of the Sun is: A) 15 million K B) 3,500 K C) 12,300 K D) 5,800 K E) 300,000 K

D) 5,800 K

Why is 21-cm radiation so important to the study of interstellar matter and the Galaxy? A) It is emitted only in hot regions of star formation, so the pattern of the spiral arms of the Galaxy can be mapped. B) It is emitted by most stars, enabling astronomers to map the entire Galaxy. C) It helps locate the galactic core in Sagittarius. D) Emitted by hydrogen, it passes through interstellar dust and lets us to map the entire Galaxy. E) Emitted by carbon monoxide, it passes through interstellar gas and lets us to see places rich in organic molecules around the Galaxy.

D) Emitted by hydrogen, it passes through interstellar dust and lets us to map the entire Galaxy.

The Main Sequence is the first stellar stage in which energy produced by ________ balances the energy lost by radiation from the surface of the star. A) Weak nuclear interactions B) Both fission and fussion C) Fission D) Fusion E) Both Fission and weak nuclear reactions

D) Fusion

What inevitably forces a star like the Sun to evolve away from being a main sequence star? A) The core loses all its neutrinos, so all fusion ceases. B) The core begins fusing iron. C) The star uses up all its supply of hydrogen. D) Helium builds up in the core, while the hydrogen burning shell expands. E) The carbon detonation explodes it as a type I supernova.

D) Helium builds up in the core, while the hydrogen burning shell expands.

While perhaps affected by rotation and magnetism, we think the lower limit for black holes is: A) the high mass star limit of 8 solar masses. B) Kelvin's limit of 0.08 solar masses. C) Einstein's limit of 25 solar masses for the main sequence stars. D) Schwarzschild's limit of 3 solar masses. E) Chandrasekhar's limit of 1.4 solar masses.

D) Schwarzschild's limit of 3 solar masses.

Just as a low-mass main sequence star runs out of fuel in its core, it actually becomes brighter. How is this possible? A) Its outer envelope is stripped away and we see the brilliant core. B) It immediately starts to fuse helium. C) It explodes. D) The core contracts, raising the temperature and increasing the size of the region of hydrogen shell-burning. E) Helium fusion gives more energy than hydrogen fusion does, based on masses.

D) The core contracts, raising the temperature and increasing the size of the region of hydrogen shell-burning.

A cloud fragment too small to form a star becomes: A) a red giant. B) a Herbig Haro object. C) a T Tauri object. D) a brown dwarf. E) a black hole.

D) a brown dwarf.

In a white dwarf, we have packed the mass of the sun into the volume of earth, so the density is: A) trillions of times greater than iron. B) dozens of times that of normal matter. C) thousands of times denser than water. D) a million times that of the Sun. E) hundreds of times greater than normal matter.

D) a million times that of the Sun.

The average density of neutron stars approaches: A) about 1018 times that of water. B) infinity. C) a million times that of normal matter. D) about 10^17 kg/m^3, similar to the density of atomic nuclei. E) a million times that of even a white dwarf.

D) about 10^17 kg/m^3, similar to the density of atomic nuclei.

Which of the following are attracted by gravity? A) antimatter B) electromagnetic radiation C) any object with mass D) all of the above E) neutrinos

D) all of the above

Interstellar gas is composed mainly of: A) carbon dioxide. B) helium. C) ammonia. D) hydrogen. E) methane.

D) hydrogen.

The light we see from the Sun comes from which layer? A) troposphere B) corona C) chromosphere D) photosphere E) ionosphere

D) photosphere

What physical property of a star does the spectral type measure? A) mass B) density C) composition D) temperature E) luminosity

D) temperature

The star's color index is a quick way of determining its: A) composition. B) mass. C) density. D) temperature. E) luminosity.

D) temperature.

The critical temperature to initiate the proton-proton cycle in the cores of stars is: A) 100 million K B) 5,800 K C) 3,000 K D) 2,300,000 K E) 10 million K

E) 10 million K

In a visual binary system with circular orbits, if in 20 years the two stars' position angles have shifted by 30 degrees, the pair's period must be: A) 360 years. B) 60 years. C) 90 years. D) 120 years. E) 240 years.

E) 240 years.

What is the net result of the proton-proton chain? A) 2 hydrogens and 1 helium are fused into 1 carbon + energy B) 2 protons make deuterium + a neutrino C) 3 helium 4 fuse to make C 12 D) 2 heliums are fused into 1 carbon, 1 neutrino + energy E) 4 hydrogens are fused into 1 helium, 2 neutrinos + energy

E) 4 hydrogens are fused into 1 helium, 2 neutrinos + energy

A nearby star has a parallax of 0.2 arc seconds. What is its distance? A) .1 parsec B) .5 parsec C) 50 parsecs D) .2 parsec E) 5 parsecs

E) 5 parsecs

What would happen if mass is continually added to a 1.4 solar mass neutron star? A) all of the above B) It will erupt as a nova. C) The star's radius would increase. D) The star would erupt as a supernova. E) The star would eventually become a black hole if it exceeded 3 solar masses.

E) The star would eventually become a black hole if it exceeded 3 solar masses.

The helium flash converts three helium nuclei to the heavier element: A) iron. B) lithium. C) boron. D) beryllium. E) carbon.

E) carbon.

What are black dwarfs? A) objects that are not quite massive enough to be stars B) the lowest mass main sequence stars C) the end result of massive star evolution D) pulsars that have slowed down and stopped spinning E) cooled off white dwarfs that no longer glow visibly

E) cooled off white dwarfs that no longer glow visibly

What natural barrier tries to prevent two protons from combining? A) antigravity B) dark energy C) the weak nuclear force D) the strong nuclear force E) electromagnetic repulsion

E) electromagnetic repulsion

Which event marks the birth of a star? A) formation of the planetary nebula B) instability in an interstellar cloud C) collapse of an interstellar cloud D) formation of a photosphere E) fusion of hydrogen atoms into helium atoms

E) fusion of hydrogen atoms into helium atoms