True.
Yes, stars are born when gravity pulls gas and dust together from a nebula.
No, a planet does not collapse because gravity isn't strong enough to provide enough pressure to crush a planet. You might make a planet heavier and heavier as to increase its gravity but at some point the pressure in the planet's core will be high enough to support nuclear fusion and the planet will have changed into a star. At that point radiative pressure also begins to fight gravity.
Because of gravity. Only gravity can pull large clouds together with enough force to overcome gas pressure.
If enough matter comes together close enough, the collapse itself will generate enough heat (and pressure) for nuclear fusion. In other words, a star is created.
Gravity and pressure both do lots of things. In the center of a star (such as our sun, Sol) it is the gravitational force of the star's mass which holds it together as a star, rather than an expanding cloud of gas which it otherwise would be, and which also causes the high pressure that exists in the center of the star. Stars are composed of a substance known as plasma, which is a super heated gas in which all the electrons are ionized rather than being bound to atomic nuclei. It is the weight of all this plasma which presses down on the center of the star causing the extremely high pressure and temperature which allows nuclear reactions to take place. Only when atomic nuclei are under enormous pressure will they ever get close enough to undergo nuclear reactions, and that is because they are all positively charged, and therefore repel each other. So gravity and pressure, working together, make it possible for the sun and stars to shine. Without gravity and pressure the universe would be a dark, cold place.
Yes, stars are born when gravity pulls gas and dust together from a nebula.
Having some trouble seeing your list of choices from here.But stars do.
No, a planet does not collapse because gravity isn't strong enough to provide enough pressure to crush a planet. You might make a planet heavier and heavier as to increase its gravity but at some point the pressure in the planet's core will be high enough to support nuclear fusion and the planet will have changed into a star. At that point radiative pressure also begins to fight gravity.
Because of gravity. Only gravity can pull large clouds together with enough force to overcome gas pressure.
The list of choices posted with the question doesn't include anything that fits that description. It sounds something like a "star", but in a star, it would be "fusion", not "fission".
A star 'turns on' when it becomes large enough that there is enough pressure squeezing its insides to start a nuclear reaction. The pressure comes from gravity of the mass of the star. the planet Jupiter could become a star if it got significantly larger.
Gravity basically makes things come together, and keep together. For example, due to gravity: * Galaxies form and keep together * Stars form and keep together * Stars get hot enough for nuclear fusion to start * Planets form and keep together * Planets keep around their stars, instead of wandering off into space
Nuclear fusion occurs in stars due to the shear density of a star. They are so dense that the pressure in the core ionizes hydrogen, stripping them into bare atoms. The inward gravitational pull of the dense core causes the atoms to be smashed together, fusing into helium. The energy from the fusion provides enough outward pressure to counteract the core's own gravity.
Enough pressure to make the atoms (hydrogen atoms) in the gas (hydrogen - don't know about dust) to push so hard against one another that the atoms literally fuse together (which believe me requires an immense amount of power). This causes the nuclear fusion reaction that we see (and feel) in stars. It produces an immense amount of heat and light.
Gravity compresses gases at the center of a solar nebula until temperatures are high enough for nuclear fusion to occur.
If enough matter comes together close enough, the collapse itself will generate enough heat (and pressure) for nuclear fusion. In other words, a star is created.
Gravity and pressure both do lots of things. In the center of a star (such as our sun, Sol) it is the gravitational force of the star's mass which holds it together as a star, rather than an expanding cloud of gas which it otherwise would be, and which also causes the high pressure that exists in the center of the star. Stars are composed of a substance known as plasma, which is a super heated gas in which all the electrons are ionized rather than being bound to atomic nuclei. It is the weight of all this plasma which presses down on the center of the star causing the extremely high pressure and temperature which allows nuclear reactions to take place. Only when atomic nuclei are under enormous pressure will they ever get close enough to undergo nuclear reactions, and that is because they are all positively charged, and therefore repel each other. So gravity and pressure, working together, make it possible for the sun and stars to shine. Without gravity and pressure the universe would be a dark, cold place.