In a star with 15 to 20 times the mass of our Sun nuclear burning at the center stops
Yes. Iron is the only element that cannot release energy by fusion or fission.
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The iron core of an evolved massive star collapses because
Yes. That keeps the pressure from rising enough to support the core.
When the iron nuclei in the core of an evolved high-mass star start to come apart, they
Yes. It takes energy to split the nuclei apart.
In the core of a high-mass star, the formation of 'degenerate neutron matter' which consists entirely of neutrons that touch one another
Yes. The core collapse stops and rebounds.
The final core collapse that leads to a supernova is ended when
Yes. Neutrons will not occupy each others space, so the core cannot get smaller.
The origin of the energy that is released in a supernova explosion is
Yes. The same energy you release when you drop something.
The gravitational energy that is released when the core of a massive star collapses is usually
Yes. A major fraction of the core's mass is converted to energy when its gravity collapses it.
Elements with more protons and neutrons than iron (Uranium for example), are believed to have formed
Yes. The star's collapse drives the energy-consuming reactions that make elements heavier than iron and the following supernova explosion blows those elements out into space where they become part of new stars and planets.
Supernova explosions tend to
Yes. It takes an energy input to make those elements and a supernova has nothing but energy that it is trying to get rid of.
When the core of a star collapses while inside the star, the result is a
Yes. The slow and messy kind
A type I supernova occurs when
Yes. A fast and clean supernova.
Type I supernovas have the following properties:
Yes. They happen in standard-size white dwarfs.
Type II supernovas have the following properties:
Yes. Both properties come from the surrounding envelope of gas.
The "Little Green Men Standard Time" hypothesis for the repeating radio signals seen in 1968 was rejected partly because the repetition rate was
One conclusion that was drawn from the gradual slowing of the radio signals from the Crab Nebula was that they were probably
Yes. Something gradually running down.
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