Physics
Astronomical Objects
Astronomical objects refer to any celestial body or structure that exists in space, such as stars, planets, galaxies, asteroids, and comets. These objects are studied by astronomers to understand their properties, behavior, and evolution, and to gain insights into the workings of the universe.
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5 Key excerpts on "Astronomical Objects"
eBook - PDF- Bradley W. Carroll, Dale A. Ostlie(Authors)
- 2017(Publication Date)
- Cambridge University Press(Publisher)
The application of physics to astronomy, astrophysics , has proved very successful in explaining a wide range of observations, including strange and exotic objects and events, such as pulsating stars, supernovae, variable X-ray sources, black holes, quasars, gamma-ray bursts, and the Big Bang. As a part of our investigation of the science of astronomy, it will be necessary to study the details of celestial motions, the nature of light, the structure of the atom, and the shape of space itself. Rapid advances in astronomy over the past several decades have occurred because of advances in our understanding of fundamental physics and because of improve-ments in the tools we use to study the heavens: telescopes and computers. Essentially every area of physics plays an important role in some aspect of astronomy. Particle physics and astrophysics merge in the study of the Big Bang; the basic question of the origin of the zoo of elementary particles, as well as the very nature of the fundamental forces, is intimately linked to how the universe was formed. Nuclear physics provides information about the types of reactions that are possible in the interiors of stars, and atomic physics describes how individual atoms interact with one another and with light, processes that are basic to a great many astrophysical phenomena. Condensed-matter physics plays a 20 Chapter 1 The Celestial Sphere role in the crusts of neutron stars and in the center of Jupiter. Thermodynamics is involved everywhere from the Big Bang to the interiors of stars. Even electronics plays an important role in the development of new detectors capable of giving a clearer view of the universe around us. With the advent of modern technology and the space age, telescopes have been built to study the heavens with ever-increasing sensitivity. No longer limited to detecting visible light, telescopes are now capable of “seeing” gamma rays, X-rays, ultraviolet light, infrared radiation, and radio signals.
eBook - PDFPossible Worlds in Humanities, Arts and Sciences
Proceedings of Nobel Symposium 65
- Allén Sture(Author)
- 2010(Publication Date)
- De Gruyter(Publisher)
In this way, both theoretical work and observa-tional developments can jointly refine, modify and test the physical consistency of the scenario. Astrophysicists and cosmologists are working on ambitious problems where we are still groping for glimmerings of understanding and data are fragmentary. Satisfaction must come from continuing debate and influencing a growing consensus rather than from achieving any quick finality. Astrophysicists spend much of their time applying everyday physics, such as Newtonian gravity, atomic physics, and electromagnetism. They use physics as a tool: their mode of thinking is like that of an engineer, trying to construct a working model from known components to meet given specifications. They must always be mindful, though, that some essential component could be missing: conceivably there are physical processes that are crucial in some cosmic phenomena (quasars, for instance) which have no discernible influence on any local phenomena. The most substantial and secure progress has been in understanding the structure and life-cycle of ordinary stars: their birth from an interstellar cloud, their prolonged stable life powered by nuclear fusion, and their eventual deaths -a quiet demise as a white dwarf, or (for heavier stars) final explosion as a supernova Physicists have an extra motive for exploring phenomena where conditions are specially exotic or extreme, and we may not (from experiment) have confident knowledge of the appropriate physics. The Universe offers a cosmic laboratory for studying how material behaves under conditions that cannot be simulated terrestrially. 2. Gravitation and general relativity One branch of basic physics dependent on astronomical data is, of course, gravitation. For planets, stars ana all large astronomical systems, gravity is the controlling force. On the Earth, and throughout the Solar System, Newtonian 398 M.J.Rees theory (the inverse square law) is an excellent approximation.
- Britannica Educational Publishing, Erik Gregersen(Authors)
- 2009(Publication Date)
- Britannica Educational Publishing(Publisher)
STRONOMICAL OBJECTS AND THEIR MOTIONSO rdinary classical mechanics can describe the motion of a car on a highway, a baseball clearing the outfield fence, or an apple falling from a tree. The same equations that describe the motion of the car, the baseball, and the apple can be applied to the motion of celestial bodies acted on by any of several types of forces. By far the most important force experienced by these bodies, and much of the time the only important force, is that of their mutual gravitational attraction. But other forces can be important as well, such as atmospheric drag on artificial satellites, the pressure of radiation on dust particles, and even electromagnetic forces on dust particles if they are electrically charged and moving in a magnetic field.CELESTIAL MECHANICS
The term celestial mechanics is sometimes assumed to refer only to the analysis developed for the motion of point mass particles moving under their mutual gravitational attractions, with emphasis on the general orbital motions of solar system bodies. This science has evolved from an ad hoc collection of rules of thumb to describe the planetary motions to a finely tuned description of astronomical motion based on Newton’s laws and their fullest description in Einstein’s theory of general relativity.The term astrodynamics is often used to refer to the celestial mechanics of artificial satellite motion. Dynamic astronomy is a much broader term, which, in addition to celestial mechanics and astrodynamics, is usually interpreted to include all aspects of celestial body motion (e.g., rotation, tidal evolution, mass and mass distribution determinations for stars and galaxies, fluid motions in nebulas, and so forth).EARLY THEORIESCelestial mechanics has its beginnings in early astronomy, in which the motions of the Sun, the Moon, and the five planets visible to the unaided eye—Mercury, Venus, Mars, Jupiter, and Saturn—were observed and analyzed. The word planet
eBook - PDF- Cynthia Phillips, Shana Priwer(Authors)
- 2024(Publication Date)
- For Dummies(Publisher)
Astronomy is essentially a science of observation, whereas astrophysics is more concerned with under- standing those observations. Gear up and let’s dive in! The start of astronomy The first few thousand years of astronomy can be seen as largely descriptive. Humans around the world documented the sky, observed changes, and made up stories to explain what they saw. These stories were recorded into the names of the constellations, and they were created by cultures all around the world. People observed that although most stars had fixed patterns in the sky, there were also repeating patterns. The Sun rose and set predictably, for example. Early observers noted a few interlopers: Stars that changed position over the course of the year were later shown to be planets, and flashy visitors such as the occasional comet and meteor made their own appearances. As time went on, astronomical observations became more rigorous as telescopes were invented and used to observe the sky in more detail. Astronomers soon dis- covered that there was more to the sky than sparking points of light. Although most of these objects were stars, 19th-century telescopes and the discovery of photography revealed the larger, fainter, and fuzzier objects as nebulae and CHAPTER 1 Welcome to the Universe 11 galaxies. With this expanded cast, the stage was set, and interest in the cosmos was sufficiently piqued to incite an entirely new field of study, one that stretched both imaginations and creativity to the maximum. A beautiful connection: Physics, astronomy, and astrophysics Physics, as you might recall from high school, is the study of how the natural world works. If you drop a can of beans on your toe, that’s gravity at work. Astronomy, on the other hand, is the study of everything in the sky, from planets to stars to galaxies. Astrophysics joins the party as a more quantitative study that combines the observations of astronomy (“what”) with the underlying theories of physics (“how”).
eBook - PDF- Mendel Sachs(Author)
- 2010(Publication Date)
- ICP(Publisher)
1 Physics of the Universe Introduction Physics is the science of inanimate matter. Cosmology is the part of this science that deals with the universe as a whole. It is the oldest and the youngest branch of physics. It is the oldest because the heavens were studied in ancient times, in Greece and in Asia, and other parts of the world. It is the youngest because it has been re-invigorated in recent times due to observations with new, high-resolution astronomical instrumentation (such as the Hubble telescope) and theoretical analyses in the context of current thinking in particle physics and relativistic dynamics. Voluminous works have been written on the order of the night sky. ( The Greek word , ‘ Cosmology ’, means ‘ order ’ ( logos ) of the cosmos .) 1 Astronomical laboratories have been constructed since the ancient times to study this order. Examples include the Stonehenge monument, built by the ancient Britons thousands of years ago, and similar ancient astronomical viewing sites in India, China, Australia, Peru, Mexico and from other cultures in the different corners of the world, designed by the ancient and aboriginal peoples to see the star formations and their locations, the locations of the sun and the moon, at the different times of the year. In these ancient viewings, there was no magnification. Galileo, in the 16th century, was the first astronomer to use magnification, utilizing the telescope — a series of lenses that he 1 2 Physics of the Universe contrived to view the heavens. 2 Focusing mainly on our solar system, he saw the moons of Jupiter, the sun spots, the landscape of the moon, and he verified the conclusion of Copernicus that the earth moves ! However, Galileo went further than Copernicus, who theorized that the sun is at the absolute center of the universe, and that the earth orbits about it, along with the other planets of the solar system.
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