Supernovas are among the most energetic events in the universe and result in the
complete disruption of stars at the end of their lives. Originally, the distinction
between Type I and Type II supernovas was based solely on the presence or absence
of hydrogen atoms (hydrogen lines). Supernovas without hydrogen lines were
called Type I, while those with hydrogen lines were Type II. Subsequent analysis
of many of these events revealed that this empirical classification schema instead
reflected two different mechanisms for the supernova explosion.
Type I supernovas happen in binary stars — two stars that orbit closely each
other — when one of the two binary stars is a small, dense, white dwarf star. If the
companion star ranges too close to the white dwarf that it is orbiting, the white
dwarf’s gravitational pull will draw matter from the other star. When the white
dwarf acquires enough matter to become at least 1.4 times as big as the Sun, it
collapses and explodes in a supernova.
Type II supernovas occur when a star, much more massive than the Sun,
ends its life. When such a star begins burning out, the core of the star quickly
collapses releasing amazing energy in the form of neutrinos, a kind of particle
smaller than even an atom. Electromagnetic radiation — energy that is electric and
magnetic — causes the star to explode in a supernova. Whereas Type I supernovas
typically destroy their parent stars, Type II explosions usually leave behind the
stellar core.
The classification schema regarding the mechanism for supernova explosions
helps to more succinctly answer the question: Is the Sun in danger of becoming
a supernova? Neither does our Sun have a companion star orbiting it nor does
our Sun have the mass necessary to become a supernova. Furthermore, it will be
another billion years until the Sun runs out of fuel and swells into a red giant star
before going into a white dwarf form.
How is this passage organized?
A) A single phenomenon is introduced and two overlapping classification schemas are
contrasted.
B) An original theory is mentioned before being overturned as a result of new findings.
C) Two complementary mechanisms for describing a single phenomenon are discussed
and a conclusion is offered.
D) A new classification schema is described and an example of how it works is provided.
E) Two different classification systems are outlined and a question posed to help
reconcile both.
It can be inferred from the passage that
A) Classifying a Type I or Type II event based on the presence or absence of hydrogen is
not necessarily incompatible with a classification schema based on the mechanism
by which these two events explode.
B) A dense white dwarf’s gravitational pull on its companion star causes the companion
star to collapse and explode as a supernova.
C) Before a star such as the Sun can become a red giant, it must first become a white
dwarf.
D) In a Type II supernova, energy and electromagnetic radiation causes a star to collapse
and explode.
E) Supernovas are rare events in our universe.
Which of the following best summarizes the author’s answer to the question: Is the Sun in
danger of becoming a supernova?
A) The Sun is too large to have a white dwarf as a partner and lacks the physical size
required to become a red giant.
B) Even if the Sun were paired with a white dwarf, the Sun does not have the mass
necessary to create sufficient electromagnetic radiation.
C) The Sun is not a white dwarf with a companion star orbiting it, nor does it have the
size to qualify as a Type II supernova.
D) Without a white dwarf orbiting the Sun, the Sun has no obvious way to increase its
size to become a Type II supernova.
E) The Sun will inevitably become a supernova once it passes from a red giant to white
dwarf but not for at least a billion years.
According to the passage, which statement or statements below are true?
I. The energy created from a Type II explosion is greater than the energy created by a
Type I explosion.
II. The sun is not a binary star.
III. Both Type I and Type II supernovas result in the complete destruction of the exploding
star.
A) I only
B) II only
C) I and III only
D) II and III only
E) I, II, and III
OA after discussion. A pretty tough passage. Enjoy
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