- The variations in brightness (on timescales of 1-100 days) of a red giant star are due to what physical process?
(a) expansion and contraction of the star due to instabilites between gravity and pressure
(b) accretion and subsquent explosion of mass onto an unseen, compact companion
(c) changes in the Earth's atmosphere which ``blur'' the image of such a bright star
(d) shockwaves from violent iron fusion occuring in the core of this type of star
(e) the periodic eclipsing of its surface by a cooler companion star
- During the final stages of a massive star's life, what two products are released when a proton merges with an electron in its dense, iron core?
(a) neutrons and neutrinos
(b) neutrons and microwaves
(c) gamma-rays and quarks
(d) neutrinos and microwaves
(e) it is not possible for an electron to merge with a proton
- Which of the following does NOT happen has a result of core collapse at the end of the life of a massive star?
(a) The core density approaches the density of an atomic nucleus (``nuclear density'').
(b) Electrons combine with protons to make neutrons.
(c) Great numbers of neutrinos are produced.
(d) The collapsed core rapidly becomes a white dwarf star.
(e) A shockwave propogates outward, expelling the outer layers of the massive star into the interstellar medium.
- The material that makes up the Sun was once part of
(a) the Big Bang.
(b) another star.
(c) a molecular cloud.
(d) a protostar.
(e) all of the above.
- Why is a red giant so large?
(a) The helium-rich core has expanded, pushing the outer layers of the star outward
(b) Red giants rotate rapidly, causing the outer layers of the star to expand.
(c) It is an optical illusion caused by the Earth's atmosphere.
(d) Pressure from nuclear reactions in the core and surrounding shells cause expansion.
(e) The star has many, many times the mass of the Sun.
- If cold molecular clouds are visibly ``dark'', then how do we observe them?
(a) Molecular gas clouds give off copious amounts of gamma-ray emission.
(b) The rotation and vibration of the molecules in these clouds emit microwaves.
(c) Only molecular clouds in which stars are forming are detectable.
(d) Interstellar molecular gas clouds are excellent X-ray emitters.
(e) We can't observe molecular clouds - they are theoretical predictions.
- What are the main by-products of helium nuclear ``burning'' in red giant stars?
(a) hydrogen nuclei by photo-disintegration
(b) gamma rays, a form of electromagnetic energy
(c) iron nuclei
(d) elements more massive than iron
(e) carbon and oxygen nuclei
- The planets in our solar system formed out of:
(a) red giants
(b) comets
(c) the debris in the protostellar disk
(d) black holes
(e) carbon and oxygen
- The lower left corner of the H-R diagram is home to which of the following?
(a) hot and very luminous
(b) on the main sequence
(c) red giants
(d) blue supergiants
(e) white dwarfs
- What is the correct explanation of the bending of a beam of light (a photon) as it passes close to a massive object like the Sun?
(a) The gravitational field interacts with the electromagnetic field of the photon to bend its path.
(b) The gravitational field of the massive object changes the refractive index of the nearby space, which causes the path of the photon to be bent.
(c) The photon travels across and must follow the curved spacetime surrounding the massive object.
(d) The photon follows the magnetic field lines of the Sun, and therefore is bent.
(e) The photons are attracted gravitationally to the massive object.
- The diameter of a typical neutron star (with a mass of 2 solar masses) is predicted to be about
(a) 1 km
(b) the same size as the Sun
(c) the size of an average city, 10-15 km
(d) that of the Earth (12,800 km)
(e) the same size as a white dwarf (just more massive)
- Pulsars are
(a) rapidly rotating neutron stars detected by their radio ``signatures''
(b) interstellar beacons manufactured by small, green aliens
(c) black holes, with hot material accreting onto their surfaces
(d) close binary star systems, in which the stars undergo rapid and regular eclipses
(e) pulsating variable stars, such as red giants and supergiants
- In which of the following locations are clumps of gas likely to be collapsing to form stars?
(a) in the outer parts of our solar system, in the Oort belt
(b) in the dense cores of giant molecular clouds
(c) in the dense cores of globular clusters
(d) in hot, glowing emission nebulae
(e) in the million-degree interstellar medium that pervades our Galaxy
- The explosion of a supernova leaves behind
(a) a rapidly rotating shell of gas, dust and radiation, but no central object
(b) a rapidly expanding shell of gas and a compact white dwarf at its center
(c) a binary system of a massive star and a neutron star companion
(d) nothing; the explosion converts all matter into energy, which then radiates into space
(e) a rapidly expanding shell of gas and a central neutron star
- Select the statement that is incorrect.
(a) A 15 solar mass star has a shorter main sequence lifetime than the Sun
(b) White dwarfs are much smaller than neutron stars
(c) A Cepheid Variable is a Red Giant star
(d) The Sun's main sequence lifetime is about 10 billion years
(e) A Red Giant is a cooler star than the Sun
- What wavelength(s) would be suitable for studying molecular clouds?
(a) Visual
(b) infrared
(c) radio (microwave)
(d) infrared and radio (microwave)
(e) x-ray and gamma rays
ANSWERS: 1 (a), 2 (a), 3 (d), 4 (e), 5 (d), 6 (b), 7 (e), 8 (c), 9 (e), 10 (c), 11 (c), 12 (a), 13 (b), 14 (e), 15 (b), 16 (d)