What is a star?

Question

Well of course they twinkle at night and we see them like every night. First I wanna say what's the difference between a star and a planet? How are stars different than planets? Are stars always bigger than the sun or earth?

Are stars hot or cold?

Isn't Jupiter, Saturn, Neptune, Uranus Gaseous, they're not solid?

Answer 1

Stars are lumps of matter massive enough to sustain fusion reactions in their cores and produce light and heat. If planets were big enough they would ignite too and become stars: Jupiter would be a star if it were just ten times more massive than it is - lucky for us it isn't.

Stars spend most of their lives with hydrogen as fuel. When that runs out they turn to heavier elements, until finally there is nothing left and something has to give. Depending on the mass of the star, it could collapse into a white dwarf, planet-sized but super dense and still shining for a very long time. Heavier ones become neutron stars after exploding into novas or supernovas, so dense a teaspoonful might be as massive as a mountain. Still heavier ones can collapse into black holes (which like global warming were once theoretical but now no one doubts their reality).

If a star is extremely massive it will burn its nuclear fuel quickly - these are the blue giants, which may last only a million years or so. Our sun is right in the middle with a lifetime of about ten billion years, enough time for humans to evolve and wonder what it's all about. The sun is now halfway through its lifespan, but more than halfway through its life-sustaining period; it will eventually expand into a red giant out to the orbit of Mars, vaporizing all the inner planets.

Answer 2

(m)

A star is a massive, compact body of plasma in outer space that is held together by its own gravity and is sufficiently massive to sustain nuclear fusion in a very dense, hot core region. This fusion of atomic nuclei generates the energy that is continuously radiated from the outer layers of the star during much of its life span.

Astronomers can determine many of the properties of a star by observing its spectrum, luminosity and motion through space. Individual stars differ in their total mass, chemical composition, and age. The total mass of a star is the principal determinant in its evolution and eventual fate. Other characteristics of a star that are determined by its evolutionary history include the diameter, rotation, movement and temperature. A plot of the star's temperature against luminosity, known as a Hertzsprung-Russell diagram (HR-diagram), allows the current age and evolutionary state of the star to be determined.

A star begins as a collapsing cloud of material that is primarily composed of hydrogen, with some helium and heavier trace elements. Once the stellar core is sufficiently dense, a portion of the hydrogen is then steadily converted into helium through the process of nuclear fusion. The remainder of the star's interior carries energy away from the core through a combination of radiation and convective processes. At the surface this energy generates a stellar wind and is radiated out into space.

Once the hydrogen fuel at the core is exhausted, a star of at least 0.4 times the mass of the Sun expands to become a red giant, fusing heavier elements at the core, or in shells around the core. It then evolves into a degenerate form, recycling a portion of the matter into the interstellar environment where it will form a new generation of stars with a higher proportion of heavy elements.

Binary and multi-star systems consist of two or more stars that are gravitationally bound, and generally move around each other in stable orbits. When two such stars have a relatively close orbit, their gravitational interaction can have a significant impact on their evolution

Answer 3

As others have said, stars are huge nuclear furnaces that convert hydrogen to helium through nuclear "fusion."

Stars are a balancing act between the gravitational pressure of their massive size wanting to collapse in and the heat/energy of fusion pushing out. When this equilibrium is disrupted stars can give off huge clouds of gas, or even explode (ie. Supernova).

Jupiter is what we call a protostar. It is made up largely of hydrogen and helium, its just not large enough for its core to collapse into nuclear fusion. Some stars are the size of our sun, some are larger, and some are smaller. Stars burn at different temperatures and have different lifetimes (some millions of years, some billions.)

Answer 4

Stars are H U G E gaseous bodies, made up mostly of hydrogen.
Stars are like the sun, they're not solid like planets. They emit light because the burn steadily due to a nuclear reaction we call "fusion".

Answer 5

Star is a huge ball of burning gas while planets are celestial bodies that surround such star and our sun is a star.They are very different..........Maybe somes star are do bigger than our sun and they are classified as dwarfs intact and very small compared to other star, Medium star like our sun they are huge and has a life span of around 11 million years,giant and super giants huge ball of extremely heated gas approximately reaching about some 90k degrees C but they have only have shorter life compared to medium stars. Deinitely stars can't be as the size of a planet....

Answer 6

Our sun is a star. Other stars are the suns of other galaxies. It is my understanding that they are constantly undergoing chemical reactions that cause them to give off heat and light energy.

Suns are always larger than the planets that orbit them, or the planets in their galaxy. The reason planets orbit the sun is gravity. The law of gravity states that smaller bodies are attracted to larger bodies.

Answer 7

Stars are on fire and emit light. Planets are lumps of rock which usually rotate around stars as the stars are somewhat bigger.