Nuclear Fusion

The stars produce their heat from nuclear fusion reactions. Work on earth to produce controllable nuclear fusion is concentrating on one particular reaction, between deuterium and tritium, because it is the easiest to get going (though hard enough!). Stars operate with other reactions but all of the nuclear fusion type. You can read more in Wikipedia 'Nuclear fusion'

The process generating solar energy is one of nuclear fusion.

It is generally thought that as the gasses needed to create a star collect, the gravity that is pulling them together will compress and heat that gas so much that at some point fusion will spontaneously begin.

In the most common stellar fusion, helium gas is formed from the fusion of hydrogen nuclei.

No

Strontium is produced by nuclear fission not fusion.

The earliest attempts at fusion reactor design used magnetic confinement to compress the fuel plasma as well as keep it away from the reaction vessel walls. The best such designs were derived from the Russian tokamak toroidal reactors.

Newer attempts use inertial confinement (like H-bomb secondaries) and have come much closer to break-even than tokamak types have. No magnetic fields are used here.

Fact: Radioactive materials such as uranium are used as fuel in nuclear reactors to produce nuclear energy through a process called nuclear fission, where atoms are split to release energy.

Fib: Radioactive materials used in nuclear energy production can explode like a nuclear bomb.

All I know is that it's either the core, chromosphere, convection layer, or the corona. Which one is it?

Nuclear fusion requires extremely high temperatures and pressures, which are typically found in stars like the Sun. The cores of planets do not have the same conditions necessary for sustained fusion reactions to occur, so the fusion process is not able to take place there.

Because when a fusion reaction occurs a hydrogen atom collides with another proton, releasing energy and creating a helium nuclei. This will then collide with another proton, releasing more energy and the next atoms in the periodic table. This continues to happen as a chain-reaction similar to dominoes.

Neither, a CAT scan is one where computers are used to synthesise an image, but the radiation used is usually X-rays, though positron emission can be used, in this case it will be using appropriate radiation sources. Fusion and fission don't come into it.

In order for nuclear fusion to occur, the core of the Sun must be hot enough to overcome the electrostatic repulsion of the nuclei. This repulsion arises from the positive charges of protons in the atomic nuclei, which repel each other. The extreme temperatures in the Sun's core, reaching around 15 million degrees Celsius, provide the necessary energy for particles to collide with sufficient force to allow fusion to take place, releasing vast amounts of energy in the process.

The dominant nuclear reaction in the Sun is the proton-proton chain reaction, with the net reaction being four hydrogen atoms turning into a helium atom (actually, it's too hot for atoms to exist in the core of the Sun where this happens, and really what happens is that four hydrogen nuclei turn into a helium nucleus plus two positrons, two electron neutrinos, and some gamma radiation).

Star

The positive charges of hydrogen nuclei cause repulsion, it is very difficult to bring two hydrogen nuclei close enough for them to fuse into helium. However, if they can be forced to fuse, a huge amount of energy is released.

Ever since the earth formed and the sun burst into light, the sun's light, which is created from nuclear fusion on our local star, has warmed the earth from the outside. Sunlight is directly responsible for the continuation of life on earth. If the sun suddenly went dark, most life on earth would die, and the rest would freeze solid in a ball of ice.