(understanding astronomical phenomena in terms of the laws of physics)

Physical composition of the stars

  • Astrophysics is devoted to the understanding of astronomical phenomena in terms of the laws of physics.
  • The first book on the physical sciences, Newton's Principia, laid the foundations both of physics and of astronomy.
  • Besides common atoms; such as, carbon dioxide, carbon monoxide, and water vapor; large molecules with atomic weights exceeding one hundred have been identified.
  • The study of these interstellar lines has played central roles for the delineation of the spiral arms in the milky way and in the location of the seats of the formation of the stars.
  • There have been recent advances in "relativistic astrophysics" in which one has applied the principles of general relativity to deduce the last stages in the evolution of stars, the structure of pulsars, and the formation of black holes.
  • Researchers have uncovered how giant magnetic fields up to a billion, billion miles across; such as, the one that envelopes our galaxy, are able to take shape despite a mystery that suggested they should collapse almost before they'd begun to form.
  • Astrophysicists have long believed that as these large magnetic fields grow, opposing small-scale fields should grow more quickly, thwarting the evolution of any giant magnetic field.
  • Astrophysicists discovered instead that the simple motion of gas can fight against those small-scale fields long enough for the large fields to form.
  • The mechanism, called a dynamo, that creates the large-scale field twists up the magnetic field lines as if they were elastic ribbons embedded in the sun, galaxy or other celestial object.
  • Turbulence kicked up by shifting gas, supernovae, or nearly any kind of random movement of matter, combined with the fact that the star or galaxy is spinning carries these ribbons outward toward the edges.
  • As they expand outward they slow and the resulting speed difference causes the ribbons to twist up into a large helix, creating the overall orderly structure of the field.
  • Modern Astrophysical Research

  • Modern astrophysics encompasses an enormous range of research activities and many branches of physical science; observations from telescopes on Earth and in space, analysis and measurements in the laboratory, and theoretical studies using pen, paper; as well as, supercomputers.
  • Astrophysicists use gravitational physics to understand how stars form, nuclear physics to understand how stars make the chemical elements, and atomic and molecular physics to identify those elements and to understand their behavior wherever they appear in the universe.
  • The first use of the term was in the 1860s when major advances were taking place in stellar spectroscopy.
  • Stellar spectroscopy is the analysis of the light of the stars by dispersing starlight into its component colors or wavelengths using a prism.
  • Spectroscopy in the laboratory was one of the foundations of atomic physics and applying these principles to the stars was the origin of astrophysics.
  • In the 20th century, astrophysics has taken on a much wider meaning than just stellar spectroscopy.
  • In the second half of the 20th century, astrophysics expanded to include the study of other types of objects, including the interstellar medium, galaxies, black holes, pulsars, quasars, and even the universe as a whole.
I wish, my dear Kepler, that we could have a good laugh together at the extraordinary stupidity of the mob. What do you think of the foremost philosophers of this University? In spite of my oft-repeated efforts and invitations, they have refused, with the obstinacy of a glutted adder, to look at the planets or Moon or my telescope.
—Galileo Galilei

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