PSU ASTRO 7N FINALS PAPER UPDATED EXAM QUESTIONS
AND ANSWERS GRADED A+
✔✔Life cycle of massive stars - ✔✔when core hydrogen is exhausted, then helium
burning in the core (while swelling into a red giant), when core helium supply is
exhausted, then carbon burning, and then even-heavier nuclei burning (all while
swelling even larger, into a red supergiant)
✔✔"onion skin" model - ✔✔concentric shells of fusion zones involving different chemical
elements, with the heaviest going on towards the core
✔✔Iron (Fe) in the sun - ✔✔iron is very stable and reactions involving iron do not
produce energy —instead they cost more energy than they release, so no further gas
pressure support for the star against its own gravitational collapse
✔✔"Type II" supernova - ✔✔a violent explosion with the star's core left behind; the
explosion itself creates a short-lived highly-energetic environment which briefly makes
possible the fusion of elements heavier than iron — like gold, silver, etc.
✔✔neutron star - ✔✔remaining core of a supernova about 1.4 - 3 x themes of the sun
and a 5-6km radius
✔✔Origins of a black hole - ✔✔Develops is a 5-6 km core is greater than 3 solar
masses
✔✔Black Holes - ✔✔the end state of the highest-mass stars ( > about 40 solar
masses), left behind after supernova explosion
✔✔event horizon - ✔✔the spherical boundary around a black hole from within which
nothing can escape —not even light (i.e., the "escape velocity" within this distance
exceeds the speed of light — "nature's speed limit," nothing can go faster)
✔✔speed of the orbit of a star - ✔✔used in a binary system with a black hole to
measure the black hole's mass
✔✔singularity - ✔✔a point of infinite density at the center of a black hole
✔✔if a star begins with a mass < about 8 solar masses: - ✔✔the core becomes a white
dwarf — collapse stops because of degeneracy pressure of electrons; core radius same
as Earth's; the white dwarf is surrounded by released outer layers —a planetary nebula
✔✔If a star begins with about 8 - 40 solar masses: - ✔✔final core-collapse is preceded
by a Type II supernova; the core becomes a neutron star — collapse stops because of
degeneracy pressure of neutrons; radius 5 - 6 km (city-size).
, ✔✔If a star begins with > about 40 solar masses: - ✔✔final core-collapse is preceded
by a Type II supernova; the core becomes a black hole — collapse does not stop; all
the mass becomes concentrated at a singularity.
✔✔Habitable Zone - ✔✔the region around a star where liquid water could be present on
a planet's surface — not too hot as to be all boiled off or dried out, and not too cold as to
be permanently frozen over
✔✔Where can extremophiles be found - ✔✔deep underground; in near or total
darkness; high acidity; high radiation; in methane ice; extreme heat and/or pressure
✔✔Drake equation - ✔✔a method to estimate the number, N, of communicating /
technological civilizations in our galaxy at a given time; originally presented by Dr. Frank
Drake of the Search for Extraterrestrial Intelligence (SETI) program
✔✔N = R x Fp x Ne x Fl x Fi x Fc x L - ✔✔The Drake Equation
✔✔Extrasolar planets - ✔✔The first extrasolar planets were discovered and confirmed
in 1992 by Penn State Professor Alex Wolszczan; rather than by a "normal" star, they
were found in orbit around a dead neutron star; these planets would be unlikely to
support life, now.
✔✔Open Star Clusters - ✔✔have hundreds, up to thousands, of stars; the stars formed
at about the same time, from the same initial gas & dust cloud; cluster only stars bound
by gravity for a few million years; tend to have lots of blue stars visible, because of
relatively young ages (and because the blues ones vastly outshine the redder ones)
✔✔Globular Star Clusters - ✔✔hundreds of thousands, to millions, of stars; tend to be
yellow in color, with a number of red giants; many have ages around 10 billion years —
overall considered old clusters
✔✔Ages of Star Clusters - ✔✔ages of star clusters can be determined by seeing what
spectral class of star has most recently "turned off" of the main sequence, in the
cluster's H-R diagram; many stars formed in clusters that later dispersed, leaving stars
more isolated
✔✔Planetary Nebulae - ✔✔a low-mass star runs out of core nuclear fuel, blows off
outer layers; have bipolar jets; lasts tens of thousands of years that can be a few light
years in size; he core of the former star, a white dwarf, is left behind at the center of the
nebula; end state of the sun
✔✔Novae (i.e. nova) - ✔✔is caused by a binary star, wherein one star of the two
evolves faster than the other
AND ANSWERS GRADED A+
✔✔Life cycle of massive stars - ✔✔when core hydrogen is exhausted, then helium
burning in the core (while swelling into a red giant), when core helium supply is
exhausted, then carbon burning, and then even-heavier nuclei burning (all while
swelling even larger, into a red supergiant)
✔✔"onion skin" model - ✔✔concentric shells of fusion zones involving different chemical
elements, with the heaviest going on towards the core
✔✔Iron (Fe) in the sun - ✔✔iron is very stable and reactions involving iron do not
produce energy —instead they cost more energy than they release, so no further gas
pressure support for the star against its own gravitational collapse
✔✔"Type II" supernova - ✔✔a violent explosion with the star's core left behind; the
explosion itself creates a short-lived highly-energetic environment which briefly makes
possible the fusion of elements heavier than iron — like gold, silver, etc.
✔✔neutron star - ✔✔remaining core of a supernova about 1.4 - 3 x themes of the sun
and a 5-6km radius
✔✔Origins of a black hole - ✔✔Develops is a 5-6 km core is greater than 3 solar
masses
✔✔Black Holes - ✔✔the end state of the highest-mass stars ( > about 40 solar
masses), left behind after supernova explosion
✔✔event horizon - ✔✔the spherical boundary around a black hole from within which
nothing can escape —not even light (i.e., the "escape velocity" within this distance
exceeds the speed of light — "nature's speed limit," nothing can go faster)
✔✔speed of the orbit of a star - ✔✔used in a binary system with a black hole to
measure the black hole's mass
✔✔singularity - ✔✔a point of infinite density at the center of a black hole
✔✔if a star begins with a mass < about 8 solar masses: - ✔✔the core becomes a white
dwarf — collapse stops because of degeneracy pressure of electrons; core radius same
as Earth's; the white dwarf is surrounded by released outer layers —a planetary nebula
✔✔If a star begins with about 8 - 40 solar masses: - ✔✔final core-collapse is preceded
by a Type II supernova; the core becomes a neutron star — collapse stops because of
degeneracy pressure of neutrons; radius 5 - 6 km (city-size).
, ✔✔If a star begins with > about 40 solar masses: - ✔✔final core-collapse is preceded
by a Type II supernova; the core becomes a black hole — collapse does not stop; all
the mass becomes concentrated at a singularity.
✔✔Habitable Zone - ✔✔the region around a star where liquid water could be present on
a planet's surface — not too hot as to be all boiled off or dried out, and not too cold as to
be permanently frozen over
✔✔Where can extremophiles be found - ✔✔deep underground; in near or total
darkness; high acidity; high radiation; in methane ice; extreme heat and/or pressure
✔✔Drake equation - ✔✔a method to estimate the number, N, of communicating /
technological civilizations in our galaxy at a given time; originally presented by Dr. Frank
Drake of the Search for Extraterrestrial Intelligence (SETI) program
✔✔N = R x Fp x Ne x Fl x Fi x Fc x L - ✔✔The Drake Equation
✔✔Extrasolar planets - ✔✔The first extrasolar planets were discovered and confirmed
in 1992 by Penn State Professor Alex Wolszczan; rather than by a "normal" star, they
were found in orbit around a dead neutron star; these planets would be unlikely to
support life, now.
✔✔Open Star Clusters - ✔✔have hundreds, up to thousands, of stars; the stars formed
at about the same time, from the same initial gas & dust cloud; cluster only stars bound
by gravity for a few million years; tend to have lots of blue stars visible, because of
relatively young ages (and because the blues ones vastly outshine the redder ones)
✔✔Globular Star Clusters - ✔✔hundreds of thousands, to millions, of stars; tend to be
yellow in color, with a number of red giants; many have ages around 10 billion years —
overall considered old clusters
✔✔Ages of Star Clusters - ✔✔ages of star clusters can be determined by seeing what
spectral class of star has most recently "turned off" of the main sequence, in the
cluster's H-R diagram; many stars formed in clusters that later dispersed, leaving stars
more isolated
✔✔Planetary Nebulae - ✔✔a low-mass star runs out of core nuclear fuel, blows off
outer layers; have bipolar jets; lasts tens of thousands of years that can be a few light
years in size; he core of the former star, a white dwarf, is left behind at the center of the
nebula; end state of the sun
✔✔Novae (i.e. nova) - ✔✔is caused by a binary star, wherein one star of the two
evolves faster than the other
