Astronomy is the science that deals with the observation and the study of all phenomena outside the Earth’s atmosphere. The word astronomy comes from the Greek word αστρονομία (astronomia), a composition of άστρον (astron, star or constellation) and νόμος (nomos, law): the granting of patterns to stars.
The astronomy studies not only stars and galaxies in the universe, but also the planets of our own solar system. Part of the astronomy Astrophysics, is a branch of physics that the processes that take place in the cosmos is trying to explain with laws of physics. Many astronomers have a solid background in physics and mathematics.
Amateur Telescope (Maksutov-Cassegrain type)
On the other hand, is one of the few Sciences where also the astronomy hobbyists or ‘ amateur astronomers ‘ can play an active role in, especially when discovering and observing transient astronomical events, such as comets and meteors. The names of many (one-time) comets, for example, are usually taken from amateur astronomers who first observed this Comet.Astrophysics and Cosmology
Astrophysics is a later development of astronomy, which became possible by the understanding that:
the Earth and all celestial bodies from the same chemical elements exist;
on Earth the same laws of physics apply as in the rest of the universe.
Cosmology is a branch of astronomy that deals with the structure, the origin, General history and future of the universe.Antiquity
Astronomy is a very old science that already existed in ancient Egypt, Sumerië, India and China. In the very beginning loved astronomy is only concerned with the movements of objects across the sky, such as Sun, Moon and planets. One could gradually spectacular phenomena, such as predict solar and lunar eclipses. Also the appearance of comets spoke very suggestive. This to the sky by Babylonian astronomers were observed phenomena associated with events on Earth, what also marked the beginning of astrology. the astronomy was in that start time limited to the objects that are visible with the naked eye. The ancient Greeks brought astronomy a piece, for example by the further definition of the Zodiac, a band of 12 constellations through which the bright sun, Moon and planets move.
Middle ages and renaissance
Astronomy and geometry in the middle ages. Objects used include an armillary sphere and a compass.
During the middle ages the development of astronomy virtually silent, with the exception of the work of some Arab astronomers. Many names of stars therefore from the Arabic tribes. During the renaissance, Copernicus proposed an astronomical model on which the Sun in the middle state of the solar system (assuming heliocentrism to be true). His work was defended and further developed by Galileo Galilei and Johannes Kepler. The latter described as first in a correct way the movements of the planets around the Sun. Kepler, however, had no insight into the underlying cause of the laws of Kepler that he intentionally employed imagery culled from his observations.
New time and date
Understanding of gravity and Heavenly dynamics were discoveries of Isaac Newton, that the movements of the planets fully stated.
It was discovered that stars very far removed from us. With the invention of spectroscopy was proven that stars are similar objects as our own Sun, but with a wide variety of temperatures, masses and sizes. That our Galaxy consists of a separate group of stars was only proven in the 20th century. When were also discovered other galaxies and nebulae and gas clouds. Shortly after the expansion of the universe was shown on the basis of the redshift that arises by the doppler effect. This shows that most of these other galaxies moving away from us.
Initially we believed that the solar system ceased in the orbit of Pluto. A problem, however, remained the origin of comets with hyperbolic orbits, which indicate that they are often very large distance. The astronomer Jan Oort in 1950 proposed the Oort Cloud for: a reservoir of billions of comet-like bodies that are left after the formation of the solar system and extends up to one or two light years around the solar system. In 1951 the existence of the Kuiper belt was suggested by the Dutch-American Gerard Kuiper. The kortperiodieke comets would come here; i.e. the comets with a period of between 50 and a few thousand years and with the largest concentration of Comet bodies just beyond the orbit of Neptune. Meanwhile, there are already several dimensions of objects between the comets and Pluto in found in these belts that most likely the existence is proven.
The field of cosmology was with huge leaps forward in the 20th century by the model of the big bang. A theory that by evidence from astronomy and physics is supported, such as the cosmic microwave background radiation, Hubble’s law and the relative prevention of the various elements in the universe.
The star 51 Pegasi In 1995 was the first planet outside the solar system discovered by using better telescopes. In the ensuing years, there are still many more of these extrasolar planets discovered.
With the advent of the space are astronomical discoveries in a big gear. From general relativity follows the possibility of the existence of black holes, which are indirectly observed.Observations
The domes of the Keck Observatory in Hawaii
Information about astronomical objects can only be obtained by observations. Most observations will be done by means of detection and analysis of electromagnetic radiation, so photons. Another source of information is the cosmic radiation, such as neutrinos. It is expected that in the future also gravity waves information about cosmic events could convey to us.
The optical astronomy uses visible light. The most commonly used instrument is the telescope, supplemented with electronic image processing techniques and spectrograms.
The infrared astronomy observations from performs at longer wavelengths than those of visible light. Also this is done by using telescopes, which are specially designed for observing infrared. Because infrared light is strongly absorbed by water vapor, infrared observations are usually performed at high locations, such as on a mountain. Known locations are the observatories on the high Andes in Chile, Hawaii, and the Canary Islands. Formerly also used balloons that were often instruments at high altitude observations did. The space telescope has even greater benefits, because it still more noise from the atmosphere can be eliminated.
Radio Astronomy uses entirely different instruments, namely radio telescopes to radio radiation with a wavelength of millimeters or centimeters. The recipients seem on the receivers for normal radio reception. Currently builds ASTRON (Netherlands foundation for research in astronomy) the largest radio telescope in the world, LOFAR.
For x-rays, gamma rays and ultraviolet radiation is the atmosphere almost opaque, with the exception of a few wavelengths, where the atmosphere is transparent. These observations are so often also done from space, or from balloons. The x-ray astronomy using satellites in particular led to many new insights.
Since some years the SETI Project searches for signals from the universe that on different life.