Concept
Star
Overview
A star is a luminous spheroid of plasma held together by self-gravity. 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 stars and provide standardized stellar designations. The observable universe contains an estimated 1022 to 1024 stars. Only about 4,000 of these stars are visible to the naked eye—all within the Milky Way galaxy.
A star's life begins with the gravitational collapse of a gaseous nebula of material largely comprising hydrogen, helium, and traces of heavier elements. Its total mass mainly determines its evolution and eventual fate. A star shines for most of its active life due to the thermonuclear fusion of hydrogen into helium in its core. This process releases energy that traverses the star's interior and radiates into outer space. At the end of a star's lifetime, fusion ceases and its core becomes a stellar remnant: a white dwarf, a neutron star, or—if it is sufficiently massive—a black hole.
Stellar nucleosynthesis in stars or their remnants creates almost all naturally occurring chemical elements heavier than lithium. Stellar mass loss or supernova explosions return chemically enriched material to the interstellar medium. These elements are 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 in the sky over time.
Stars can form orbital systems with other astronomical objects, as in planetary systems and star systems with two or more stars. When two such stars orbit closely, their gravitational interaction can significantly impact their evolution. Stars often form part of much larger gravitationally bound structures, such as star clusters and galaxies.
Overview adapted from Wikipedia (CC BY-SA 4.0; see the article history for authors).
In the original texts
Passages from public-domain books where Star is discussed.
9. The ninth aspect is called vespertine setting; when the star, together with the Sun, is on the occidental horizon. One form of this aspect is the vespertine, succedent and visible setting; when the star, at the commencement of its occultation, sets immediately after the Sun: another is the precise vespertine setting; when the star sets at the same moment with the Sun: another is the precedent, invisible setting…
Ptolemy, Ptolemy's Tetrabiblos
names the idea; states what it is; the book is about it; opens on it
Aristotle, that the heavenly bodies require no nutriment, for they being eternal cannot be obnoxious to corruption. Plato and the Stoics, that the whole world and the stars are fed by the same things. CHAPTER XVIII. WHAT ARE THOSE STARS WHICH ARE CALLED THE DIOSCURI, THE TWINS, OR CASTOR AND POLLUX? Xenophanes says that those which appear as stars in the tops of ships are little clouds brilliant by their peculiar…
Plutarch, Complete Works of Plutarch — Volume 3
names the idea; a chapter is titled for it; states what it is; opens on it
Thus water is set in motion by the moon-sphere, fire by the sun-sphere, air by the other planets, which move in many and different courses with retrogressions, progressions, and stations, and therefore produce the various forms of the air with its frequent changes, contractions, and expansions; the sphere of the other stars, namely, the fixed stars, sets earth in motion; and it may be that on this account, viz., on…
Moses Maimonides, The guide for the perplexed
names the idea; opens on it
Hipparchus, who can never be sufficiently commended, as one who more especially proved the relation of the stars to man, and that our souls are a portion of heaven, discovered a new star that was produced in his own age, and, by observing its motions on the day in which it shone, he was led to doubt whether this does not often happen, that those stars have motion which we suppose to be fixed. And the same individual…
the Elder Pliny, The Boys' and Girls' Pliny
names the idea; a chapter is titled for it; opens on it
A dark veil or coloured glass has the same effect, for, upon placing them before the eye between it and the stars, all the blaze that surrounds them leaves them at once. A telescope also accomplishes the same result, for it removes from the stars their adventitious and accidental splendours before it enlarges their true discs (if indeed they are of that shape), and so they seem less magnified than other objects, for…
Galileo Galilei, The sidereal messenger of Galileo Galilei
names the idea; a chapter is titled for it; opens on it
Philosophers who discussed Star
Related ideas
- Epicurus
- Giordano Bruno
- Isaac Newton
- Planck (spacecraft)
- Ancient Greek philosophy
- Latin
- Richard Bentley
- Library of Congress
- Neptune
- Mass
- Moon
- Mercury (planet)
- Atomic nucleus
- Mesopotamia
- Babylon
- Astrology
- Oxygen
- Planet
- Greek mythology
- Photon
- Ptolemy
- Myth
- Polymath
- Observable universe
Place in the tradition
Part of Ionian school (philosophy).