Self-study
It has been hypothesized that our solar system was formed from a cloud of gas and dust produced by a supernova—an especially powerful explosion of a star. ██████████ ███████ ███ ███████ ████████ ██ ██ ████ ██████████ ████ ████████ ████ ███████ █████ ████ ████ ███████ ██ ███ █████ ███████ ██ ███ █████ ███████ ███ ███████████ ████ █████ ██ ███████ ██ ██████████ ████ ██████ █████ ██ ███ █████ ████████ ████████ ███████ ██████████ ███ ███████████
Summary
The author concludes that our solar system was not formed from a cloud of gas and dust from a supernova.
What makes the author think this?
Because if the solar system WERE formed from a cloud of gas and dust from a supernova, then the isotope iron-60 would have been present in the early history of the solar system.
But researchers haven’t found iron-60 in meteorites that formed early in the solar system’s history.
Notable Assumptions
The author assumes that if iron-60 was present in the early history of the solar system, then researchers would have been able to find it in meteorites that formed early in the history of the solar system.
4.
Which one of the following ██ ██ ██████████ ████████ ██ ███ █████████
a
If a meteorite ██ ██████ █████ ██ ███ █████ ████████ ████████ ██ ████████ ████████ ████████ ████ ███ ████████ ██ ██ █████ ██ ███ ███ ████ ████████ ██ █ ██████████
Not necessary, because what matters is whether, if iron-60 were present early in the solar system’s history, it would be found in meteorites from that period. Whether the meteorite contains other elements that aren’t produced by a supernova has no bearing on whether it would have iron-60, which we’re told is produced by a supernova.
b
Other solar systems ███ ███ ██████ ████ ██████ ██ ███ ███ ████ ████████ ██ ███████████
Not necessary, because the argument concerns our own solar system. How other solar system are formed has no bearing on what’s involved in our own solar system’s formation.
c
Supernovas do not ███████ ███████████ ██████████ ██ ███ ████ ██ ████ █████ ████ ████████
Not necessary, because even if supernovas DO produce a lot of other kinds of iron, the argument is based on our inability to find iron-60 in meteorites. There’s no indication that we’ve discovered other kinds of iron in those meteorites, so whether supernovas produced those other kinds doesn’t relate to the significance of these meteorites.
d
Researchers have found ███████ ██ ██████████ ████ ████ ██████ ██████████ ████ ██ ███ █████ ████████ ████████
Not necessary, because the argument is based on our inability to find iron-60 in meteorites from early solar system history. Whether we’ve found iron-60 in later meteorites has no bearing on early solar system history.
e
If there had ████ ███████ ███████ ██ ███ █████ ███████ ██ ███ █████ ███████ ██ █████ ██ █████ ██ ██████████ ██████ █████ ██ ███ █████ ████████ ████████
Necessary, because if this were not true — if we might NOT find iron-60 in early solar system meteorites even if iron-60 actually was present in early solar system history — then the fact we haven’t found iron-60 in the meteorites would not establish that iron-60 was not present in early solar system history. (E) must be assumed in order for our failure to find iron-60 in the meteorites to support the conclusion.