What is Stars: Definition and 890 Discussions

A star is an astronomical object consisting of a luminous spheroid of plasma held together by its own gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night, but due to their immense distance from Earth they appear as fixed points of light in the sky. The most prominent stars are grouped into constellations and asterisms, and many of the brightest stars have proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. The observable universe contains an estimated 1022 to 1024 stars, but most are invisible to the naked eye from Earth, including all individual stars outside our galaxy, the Milky Way.
A star's life begins with the gravitational collapse of a gaseous nebula of material composed primarily of hydrogen, along with helium and trace amounts of heavier elements. The total mass of a star is the main factor that determines its evolution and eventual fate. For most of its active life, a star shines due to thermonuclear fusion of hydrogen into helium in its core, releasing energy that traverses the star's interior and then radiates into outer space. At the end of a star's lifetime, its core becomes a stellar remnant: a white dwarf, a neutron star, or, if it is sufficiently massive, a black hole.
Almost all naturally occurring elements heavier than lithium are created by stellar nucleosynthesis in stars or their remnants. Chemically enriched material is returned to the interstellar medium by stellar mass loss or supernova explosions and then recycled into new stars. Astronomers can determine stellar properties including mass, age, metallicity (chemical composition), variability, distance, and motion through space by carrying out observations of a star's apparent brightness, spectrum, and changes in its position on the sky over time.
Stars can form orbital systems with other astronomical objects, as in the case of planetary systems and star systems with two or more stars. When two such stars have a relatively close orbit, their gravitational interaction can have a significant impact on their evolution. Stars can form part of a much larger gravitationally bound structure, such as a star cluster or a galaxy.

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  1. A

    How Do Binary Dwarf/Neutron Stars get so close?

    I am a little puzzled with how there is a White Dwarf Binary of Five Minutes. How do they get so close?
  2. tfr000

    Why do we stigmatize unusual fears and differences?

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  3. J

    Stargazing Basics of Using a Telescope - Locating Stars (RA)

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  4. H

    Galaxy and Stars: Questions Answered

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  5. J

    Calculating Jean's length for neutral hydrogen cloud

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  6. wolram

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  7. T

    Calculating forces between stars?

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  8. S

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  9. Low-Q

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  10. Jimbob999

    Absolute Visual Magnitude of Stars

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  11. J

    How Do Scientists Determine the Composition of a Star's Core?

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  12. A

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  13. D

    Why don't all neutron stars collapse into black holes?

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  14. S

    Planck Stars & FRBs: Rovelli's Hypothesis

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  15. K

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  16. B

    Gravitational Influence of Stars in a Galaxy

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  17. R

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  18. Mustang11

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  19. J

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  20. J

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  21. Alex299792458

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  22. Ookke

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  23. diogenesNY

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  24. james gander

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  25. V

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  26. E

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  27. Daoyang

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  28. M

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  29. AtomicPunk

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  30. F

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  32. B

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  33. R

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  34. TheTuringTester

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  35. Chronos

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  36. J

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  37. B

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  38. 2

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  39. 2

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  40. wabbit

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  41. 2

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  42. Calpalned

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  43. I

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  44. thegirl

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  45. J

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  46. T

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  47. Futurestar33

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  48. T

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  49. L

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  50. O

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