What is Star: Definition and 1000 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. Moon Shine

    B Are supernovas more likely to produce neutron stars or black holes?

    I read that after explosions supernovas can ”transform” into a neutron start or into a black hole? And now I’m curious of therer any factors which can predict what thing we’re going to get after the supernova’s explosion.
  2. S

    I Neutron Star Core: Empty Obloid Cavity & Exotic Content?

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  3. HydrogenBurns

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  4. G

    A Measuring Deflection of Star Light During Eclipse: Separating Space-Time Effects

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  5. M

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  6. M

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  7. K

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  8. K

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  9. Cerenkov

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  10. L

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  12. K

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  13. M

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  14. G

    I Hubble's Law and Star Velocity

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  15. B

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  16. J

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  20. I

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  21. P

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  22. P

    I Can a White Dwarf Collapse into a Neutron Star Without a Supernova?

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  23. N

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  24. H

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  25. Z

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  26. D

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  27. C

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  29. Physics Dad

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  30. F

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  31. B

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  32. C

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  33. shk

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  34. M

    B When a star exhausted it's nuclear fuel

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  35. M

    I Redshift of Star Light: Proportionality to Distance & Other Theories

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  36. S

    I How to differentiate Doppler shift from star emission

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  37. Grinkle

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  38. K

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  39. Samantha Martin

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  40. L

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  41. F

    I Variations in the speed of sound in a star

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  42. A

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    So, let me preface by saying I’m neither a scientist nor a mathematician, so am requesting some talented help here checking the accuracy of my source information and math. Regarding star formation, I got curious about how much volume of space in the interstellar medium is actually required to...
  43. J

    I If we teleport 1mm^3 of a neutron star outside it what hapens?

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  44. E

    China Develops Laser Gun Like Star Wars: Burns Through Skin

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  45. T

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  46. donielix

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  47. BillTre

    I Image of a Newly Formed Planet in a Disk Around a Star

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  48. I

    I What does L star mean in the Schechter function?

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  49. T

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  50. J

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