However, modern astronomy includes many elements of the motions and characteristics of these bodies, and the two terms are often used interchangeably today. Unlike most other fields of science, astronomers are unable to observe a system entirely from birth to death; the lifetime of worlds, stars, and galaxies span millions to billions of years. Instead, astronomers must rely on snapshots of bodies in various stages of evolution to determine how they formed, evolved and died. Thus, theoretical and observational astronomy tend to blend together, as theoretical scientists use the information actually collected to create simulations, while the observations serve to confirm the models — or to indicate the need for tweaking them.
Astronomy is broken down into a number of subfields, allowing scientists to specialize in particular objects and phenomena. Planetary astronomers also called planetary scientists focus on the growth, evolution, and death of planets. While most study the worlds inside the solar system , some use the growing body of evidence about planets around other stars to hypothesize what they might be like.
According to the University College London , planetary science "is a cross-discipline field including aspects of astronomy, atmospheric science, geology, space physics, biology and chemistry. Stellar astronomers turn their eyes to the stars, including the black holes, nebulae, white dwarfs and supernova that survive stellar deaths. The University of California, Los Angeles , says, "The focus of stellar astronomy is on the physical and chemical processes that occur in the universe.
Solar astronomers spend their time analyzing a single star — our sun. According to NASA , "The quantity and quality of light from the sun varies on time scales from milli-seconds to billions of years. The sun also helps us to understand how other stars work, as it is the only star close enough to reveal details about its surface. Galactic astronomers study our galaxy, the Milky Way, while extragalactic astronomers peer outside of it to determine how these collections of stars form, change, and die.
The University of Wisconsin-Madison says, "Establishing patterns in the distribution, composition, and physical conditions of stars and gas traces the history of our evolving home galaxy. Cosmologists focus on the universe in its entirety, from its violent birth in the Big Bang to its present evolution, all the way to its eventual death. Astronomy is often not always about very concrete, observable things, whereas cosmology typically involves large-scale properties of the universe and esoteric, invisible and sometimes purely theoretical things like string theory, dark matter and dark energy, and the notion of multiple universes.
Astronomical observers rely on different wavelengths of the electromagnetic spectrum from radio waves to visible light and on up to X-rays and gamma-rays to study the wide span of objects in the universe. The first telescopes focused on simple optical studies of what could be seen with the naked eye, and many telescopes continue that today.
But as light waves become more or less energetic, they move faster or slower. Different telescopes are necessary to study the various wavelengths. More energetic radiation, with shorter wavelengths, appears in the form of ultraviolet, X-ray, and gamma-ray wavelengths, while less energetic objects emit longer-wavelength infrared and radio waves.
The eyepiece is responsible for enlarging the image captured by the instrument. Eyepieces are available in different powers, yielding differing amounts of magnification. Faculae Bright patches that are visible on the Sun's surface, or photosphere. Filament A strand of cool gas suspended over the photosphere by magnetic fields , which appears dark as seen against the disk of the Sun.
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Finder A small, wide-field telescope attached to a larger telescope. The finder is used to help point the larger telescope to the desired viewing location. Fireball An extremely bright meteor. Also known as bolides , fireballs can be several times brighter than the full Moon.
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Some can even be accompanied by a sonic boom. Flare Star A faint red star that appears to change in brightness due to explosions on its surface. Galactic Halo The name given to the spherical region surrounding the center, or nucleus of a galaxy. Galactic Nucleus A tight concentration of stars and gas found at the innermost regions of a galaxy. Astronomers now believe that massive black holes may exist in the center of many galaxies. Galaxy A large grouping of stars. Galaxies are found in a variety of sizes and shapes. Our own Milky Way galaxy is spiral in shape and contains several billion stars.
Some galaxies are so distant the their light takes millions of years to reach the Earth. They were discovered independently by Galileo Galilei and Simon Marius. Gamma-ray The highest energy, shortest wavelength form of electromagnetic radiation. Geosynchronous Orbit An orbit in which a satellite's orbital velocity is matched to the rotational velocity of the planet. A spacecraft in geosynchronous orbit appears to hang motionless above one position of a planet's surface.
These clouds have enough mass to produce thousands of stars and are frequently the sites of new star formation. Globular Cluster A tight, spherical grouping of hundreds of thousands of stars.
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Globular clusters are composed of older stars, and are usually found around the central regions of a galaxy. Granulation A pattern of small cells that can be seen on the surface of the Sun. They are caused by the convective motions of the hot gases inside the Sun. Gravitational Lens A concentration of matter such as a galaxy or cluster of galaxies that bends light rays from a background object.
Gravitational lensing results in duplicate images of distant objects. Gravity A mutual physical force of nature that causes two bodies to attract each other. Greenhouse Effect An increase in temperature caused when incoming solar radiation is passed but outgoing thermal radiation is blocked by the atmosphere. Carbon dioxide and water vapor are two of the major gases responsible for this effect. Heliopause The point in space at which the solar wind meets the interstellar medium or solar wind from other stars.
Heliosphere The space within the boundary of the heliopause containing the Sun and the Solar System. Hydrogen An element consisting of one electron and one proton. Hydrogen is the lightest of the elements and is the building block of the universe. Stars form from massive clouds of hydrogen gas.https://trecgegacadep.tk
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Hubble's Law The law of physics that states that the farther a galaxy is from us, the faster it is moving away from us. Hydrostatic equilibrium A state that occurs when compression due to gravity is balanced by a pressure gradient which creates a pressure gradient force in the opposite direction. Hydrostatic equilibrium is responsible for keeping stars from imploding and for giving planets their spherical shape.
Hypergalaxy A system consisting of a spiral galaxy surrounded by several dwarf white galaxies, often ellipticals. Our galaxy and the Andromeda galaxy are examples of hypergalaxies. Ice A term used to describe water or a number of gases such as methane or ammonia when in a solid state. Inclination A measure of the tilt of a planet's orbital plane in relation to that of the Earth.
Inferior Conjunction A conjunction of an inferior planet that occurs when the planet is lined up directly between the Earth and the Sun. Inferior Planet A planet that orbits between the Earth and the Sun.
Mercury and Venus are the only two inferior planets in our solar system. International Astronomical Union IAU An international organization that unites national astronomical societies from around the world and acts as the internationally recognized authority for assigning designations to celestial bodies and their surface features.
Interplanetary Magnetic Field The magnetic field carried along with the solar wind. Interstellar Medium The gas and dust that exists in open space between the stars. Ionosphere A region of charged particles in a planet's upper atmosphere. In Earth's atmosphere, the ionosphere begins at an altitude of about 25 miles and extends outward about Iron Meteorite A meteorite that is composed mainly of iron mixed with smaller amounts of nickel.
Irregular Galaxy A galaxy with no spiral structure and no symmetric shape. Irregular galaxies are usually filamentary or very clumpy in shape. Irregular Satellite A satellite that orbits a planet far away with an orbit that is eccentric and inclined. They also tend to have retrograde orbits. Irregular satellites are believed to have been captured by the planet's gravity rather than being formed along with the planet.
Jansky A unit used in radio astronomy to indicate the flux density the rate of flow of radio waves of electromagnetic radiation received from outer space.
A typical radio source has a spectral flux density of roughly 1 Jy. The jansky was named to honor Karl Gothe Jansky who developed radio astronomy in Jet A narrow stream of gas or particles ejected from an accretion disk surrounding a star or black hole. Kelvin A temperature scale used in sciences such as astronomy to measure extremely cold temperatures. The Kelvin temperature scale is just like the Celsius scale except that the freezing point of water, zero degrees Celsius, is equal to degrees Kelvin.
Absolute zero , the coldest known temperature, is reached at 0 degrees Kelvin or Kepler's Second Law A ray directed from the Sun to a planet sweeps out equal areas in equal times. Kepler's Third Law The square of the period of a planet's orbit is proportional to the cube of that planet's semi major axis ; the constant of proportionality is the same for all planets.
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Kiloparsec A distance equal to parsecs. Kirkwood Gaps Regions in the main belt of asteroids where few or no asteroids are found.
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They were named after the scientist who first noticed them. Kuiper Belt A large ring of icy, primitive objects beyond the orbit of Neptune. Kuiper Belt objects are believed to be remnants of the original material that formed the Solar System. Some astronomers believe Pluto and Charon are Kuiper Belt objects. Lagrange Point French mathematician and astronomer Joseph Louis Lagrange showed that three bodies could lie at the apexes of an equilateral triangle which rotates in its plane. If one of the bodies is sufficiently massive compared with the other two, then the triangular configuration is apparently stable.
Such bodies are sometimes referred to as Trojans. The leading apex of the triangle is known as the leading Lagrange point or L4; the trailing apex is the trailing Lagrange point or L5. Lenticular Galaxy A disk-shaped galaxy that contains no conspicuous structure within the disk.