Results for “what is a star” · retrieved September 22, 2026
A star is a massive, luminous sphere of plasma held together by its own gravity, powered by sustained nuclear fusion in its core.
Answer details
Formation and Composition
Stars are primarily composed of hydrogen and helium. They form when high-density clumps within large molecular clouds of gas and dust collapse under their own gravitational force.
Energy Production
The core of a star reaches temperatures and pressures high enough to trigger nuclear fusion, which converts hydrogen into helium. This process releases energy that creates outward pressure, balancing the inward pull of gravity.
Life Cycle
Most stars spend the majority of their lives on the main sequence, a stable phase where they fuse hydrogen into helium. As they age and exhaust their fuel, they evolve into other forms, such as red giants.
Stellar Remnants
When fusion ceases, a star leaves behind a remnant, such as a white dwarf, neutron star, or black hole, depending on its original mass.
Sources 8
About this answerStar Basics
Stars are giant balls of hot gas – mostly hydrogen, with some helium and small amounts of other elements. Every star has its own life cycle, ranging from a few million to trillions of years, and its properties change as it ages....Stars form in large clouds of gas and dust called molecular clouds. Molecular clouds range from 1,000 to 10 million times the mass of the Sun and can span as much as hundreds of light-years. Molecular clouds are cold wh
August 12, 2026
Star | Definition, Light, Names, & Facts | Britannica
areas in which...have extensive knowledge, whether from years of experience gained by working...study for an advanced degree...Britannica Editors May 15, 2026 • History Table of Contents What is a star?...A star is any massive self-luminous celestial body of gas that shines by radiation derived from its internal energy sources. Of the tens of billions of trillions of stars in the observable universe, only a very small percentage are visible to th
August 23, 1998
Star
A star is a luminous spheroid of plasma held together by self-gravity. [1] The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night; their immense distances from Earth make them appear as fixed points of light. The most prominent stars have been categorised into constellations and asterisms, and many of the brightest stars have proper names. Astronomers have assembled star catalogues that identify the known sta
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What Defines a Star?
In a very broad sense, a star is simply one of those twinkling points of light you can see in the night sky. But that’s not terribly satisfying in either lexicological or physical terms. After all, we also know the sun is a star—but, by definition, we never see it in Earth’s night sky, and it’s certainly not a dot (unless you’re viewing it from well past Pluto, that is)....If such a basic definition leaves us a bit dry, then perhaps we can do bet
April 11, 2025
Imagine the Universe!
A star is a sphere of gas held together by its own gravity. The closest star to Earth is our very own Sun, so we have an example nearby that astronomers can study in detail. The lessons we learn about the Sun can be applied to other stars....A star's life is a constant struggle against the force of gravity. Gravity constantly works to try and cause the star to collapse. The star's core, however is very hot which creates pressure within the gas. T
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What is a Star? (article) | Stars
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Stars—facts and information | National Geographic
. A correct...be: Emit, emit,...Stars are huge celestial bodies made mostly of hydrogen and helium that produce light and heat from the churning nuclear forges inside their cores. Aside from our sun, the dots of light we see in the sky are all light-years from Earth. They are the building blocks of galaxies, of which there are billions in the universe. It’s impossible to know how many stars exist, but astronomers estimate that in our Milky Way ga
March 20, 2019
What is a star? | Space
The definition of a star is as rich and colorful as, well, the stars themselves. Our sun, imaged here in May 2020 by NASA's Solar Dynamics Observatory, is a medium-mass main sequence star. (Image credit: NASA/Solar Dynamics Observatory/Joy Ng)...It's easy enough to say what a star is. It's one of those bright pointy things that twinkle in the night sky. But beyond that, the actual definition of a star is as rich and colorful as, well, the stars t
January 4, 2021
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