Astronomy & Astrophysic

Q: The ________ model for pulsars explains why there are a lot more neutron stars than pulsars, since most are not at the correct angle for us to observe their pulses.

Q: The Crab Nebula and its pulsar were produced by a ________ supernova.

Q: The fast rotation of newly formed neutrons stars is due to conservation of ________.

Q: Most pulsars emit ________.

Q: A neutron star detectable by its rapid rotation and strong magnetic field is a ________.

Q: While white dwarfs have a density a million times that of normal matter, neutron stars are a ________ times denser than even white dwarfs.

Q: Only ________ stars have rotation periods of less than a second.

Q: Type ________ supernovae produce no neutron stars, only ejected debris.

Q: Neutron stars are the size of ________.

Q: ________ stars are solid, extremely dense objects.

Q: A neutron star ________ rapidly.

Q: As its name implies, the ________ star has fused its protons and electrons.

Q: A neutron star may form from a ________ supernova.

Q: Which of these is not an argument for Cygnus X-1 being a black hole? A) It is the third strongest source of X-rays in the sky. B) Spectroscopic data suggests hot gas is flowing toward the X-ray source. C) The mass of the visible star is greater than that of the X-ray source. D) The mass of the X-ray source is about 10 solar masses. E) The X-rays from the compact source vary in as little as a millisecond.

Q: The largest known black holes A) create the dark nebulae in the plane of the Milky Way. B) can be no more than 1.4 solar masses, according to Chandrasekhar. C) lie in the cores of the most massive galaxies. D) can be no bigger than a small city, just like neutron stars. E) can be no bigger than the Earth, like white dwarfs.

Q: A method for identifying a black hole is to A) look for voids in the star fields. B) look for its effects on a nearby companion. C) locate a visible star that disappears when the black hole passes in front of it. D) search for radio waves from the accretion disk. E) search for their pulsar signal.

Q: What is Cygnus X-1? A) the brightest star in the constellation Cygnus B) the leading candidate for an observable black hole binary system C) the strongest X-ray eclipsing binary system in the sky D) a millisecond pulsar with three Earth-like planets around it E) the first gamma-ray burster to be spotted in other wavelengths as well

Q: If the Sun were replaced by a one-solar-mass black hole, A) all terrestrial planets would fall in immediately. B) we would still orbit it in a period of one year. C) we would immediately escape into deep space, driven out by its radiation. D) our clocks would all stop. E) life here would be unchanged.

Q: As a spaceship nears an event horizon, a clock on the spaceship will be observed A) to run faster. B) to stop. C) to run slowly. D) to run backwards. E) to run the same as one on Earth.

Q: What can we detect from matter that has crossed an event horizon? A) gamma-ray bursts B) radio waves if the matter was traveling fast enough C) visible light D) X-rays if the matter was dense E) nothing

Q: If light from a distant star passes close to a massive body, the light beam will A) bend towards the star due to gravity. B) continue moving in a straight line. C) change color to a shorter wavelength. D) slow down. E) accelerate due to gravity.

Q: As a spaceship's velocity gets closer to the speed of light with respect to an external observer, that observer will report that A) its length will increase and its clock will run more slowly. B) its length will decrease and its clock will run faster. C) its length will increase and its clock will run faster. D) its length will decrease and its clock will run more slowly. E) None of these will happen.

Q: An observer on a planet sees a spaceship approaching at 0.5c. A beam of light projected by the ship would be measured by this observer to travel at A) 0.25c. B) 0.5c. C) c. D) 1.5c. E) 2.5c.

Q: What explanation does general relativity provide for gravity? A) Gravity is the result of curved spacetime. B) Gravity is directly proportional to the mass of the attracting body. C) Gravity is inversely proportional to the radius of the body. D) Gravity is the opposite of the electromagnetic force. E) Gravity can affect only massive particles, not massless photons.

Q: The Schwartzschild radius for a 12 solar mass star is A) 4 km. B) 15 km. C) 36 km. D) 100 km. E) 3000 km.

Q: The densely packed neutrons of a neutron star cannot balance the inward pull of gravity if the total mass is A) less than 1.0 solar masses. B) greater than Schwartzschild's limit of 3 solar masses. C) Chandrasekhar's limit of 1.4 solar masses. D) between 1.4 and 2.0 solar masses. E) not at least 25 solar masses.

Q: Which statement about black holes is true? A) Their escape velocity is greater than the speed of light. B) They form from 1.4 solar mass stars. C) They form an event horizon at twice the Schwartzschild radius. D) Their main-sequence mass was 5-10 solar masses. E) Their event horizon is a physical surface boundary.

Q: Which are the two most popular candidates for gamma-ray bursters? A) hypernova making pulsars, and mergers of two white dwarfs B) mergers of two black holes, and merger of a neutron star and a white dwarf C) hypernova making a black hole, and merger of two neutron stars D) collisions between a white dwarf and a giant, and merger of two neutron stars E) formation of uranium in the core of a supergiant, and collisions of white dwarfs

Q: Which statement about gamma ray bursters is not correct? A) They seem to be coming from far beyond our own Milky Way. B) They are scaled up X-ray bursters, with more massive objects involved. C) In seconds, they radiate enormous amounts of energy. D) Millisecond flickering implies they are tiny in size. E) The beams may be bi-polar ejections from the hypernova formation of black holes.

Q: A hypernova creates A) a black hole. B) a pulsar. C) a neutron star. D) millisecond-duration gamma-ray bursts. E) Both B and C are correct.

Q: In a hypernova, a very energetic supernova creates a A) very visible supernova remnant. B) millisecond pulsar. C) set of planets to orbit their neutron star host. D) black hole. E) white dwarf and its planetary nebula.

Q: What would happen if more mass was added to a 1.4-solar-mass neutron star? A) It would erupt as a Type I supernova. B) It could eventually become a black hole, via a hypernova explosion. C) It would grow larger, temporarily becoming a red giant again. D) All of its protons and electrons would turn into quarks. E) It would blow off mass as an X-ray burster.

Q: A proposed explanation for gamma-ray bursters is A) hypernova-making black holes and bipolar jets. B) coalescence of a neutron star binary. C) collisions between two white dwarfs. D) Both A and B are possible. E) All three are possible.

Q: You would expect millisecond pulsars to be A) part of a binary system. B) isolated in space. C) rotating slowly. D) most common in open clusters. E) collapsing rapidly.

Q: Most pulsars have a measured mass of A) about 1.4 solar masses. B) less than 1.0 solar masses. C) between 2 and 4 solar masses. D) 5.2 solar masses. E) greater than 10 solar masses.

Q: X-ray bursters occur in binary star systems. The two types of stars that must be present to make up such an object are A) a white dwarf and a neutron star. B) a contact binary system of two red giants. C) a white dwarf and a main-sequence star. D) a main-sequence or giant star and a neutron star in a mass transfer binary. E) two neutron stars in a mass transfer binary.

Q: Two-thirds of all known millisecond pulsars are found in what type of object? A) giant molecular clouds B) open clusters C) globular clusters D) emission nebulae E) extremely distant galaxies

Q: Three terrestrial-sized planets in orbits of a fraction of an AU have been found near A) Cygnus X-1. B) a magnetar. C) Supernova 1987A. D) a millisecond pulsar. E) a white dwarf.

Q: The supernova of 1054 AD produced A) a remnant still visible to the naked eye. B) a pulsar with a period of 33 milliseconds, visible optically. C) the closest known neutron star to our Sun. D) the most famous black hole. E) no remaining visible trace, as it was a Type I supernova.

Q: Neutron stars do not have A) masses greater than 1.4 solar masses. B) sizes comparable to large cities. C) strong magnetic fields. D) large surface gravities, compared to the Sun. E) rotation periods comparable to the Sun's.

Q: In the Lighthouse Model, A) the star literally turns on and off like a lighthouse beacon. B) all pulsars must have their poles pointed directly toward us. C) if the beam sweeps across us, we will detect a pulse of radiation. D) the period of pulsation must speed up as the neutron star continues collapsing. E) the period of pulsation slows down due to the drag of the remnant on its field.

Q: Pulsars A) spin very rapidly when they're young. B) are the cause of gamma-ray bursts. C) spin very slowly when they're young, and gradually spin faster as they age. D) generally form from 25-solar-mass stars. E) emit radio in all directions.

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