ستورپوهنه

د Wikipedia لخوا

A giant Hubble mosaic of the Crab Nebula, a supernova remnant

ستورپوهنه (چې اکثراً د آسټروفيزيکس په نامه هم يادېږي) د اسماني شيانو لکه ستوري، سيارې، لکۍ داره ستوري او د کهکشانونو په هکله د څېړنې يوه ساينسي زده کړه ده. په دې زده کړه کې د اسماني شيانو او د هغه شيانو چې د ځمکې د اتموسفير نه دباندې دي، د هغو د پېدايښت او اصل په هکله څېړنې او پېژندنې ترسره کېږي.دا زده کړه د تدريجي تکامل، فيزيک، کيميا، او د اسماني شيانو د حرکت او په همدې توګه د کايناتو د جوړښت او ودې په اړوند بحثونه کوي.
ستورپوهنه يوه داسې پوهنه ده چې د پخوانيو زمانو نه دود ده او د زړو علمونو نه يو علم ګڼل کېږي. که څه هم چې د ټيليسکوپ د پنځولو اړتيا ددې لامل وګرځېد چې ستورپوهنه په يو نوي ساينس بدل کړي خو د پخوانيو تمدنونو ستورپوهانو په مېتوديک ډول د شپې لخوا د اسمان کتنه ، او په همدې توګه ستورپوهنيز آرډيفکټونه هم د ډېرو پخوانيو پړاونو راپدېخوا موندل شوي دي.

د شلمې پېړۍ نه راپدېخوا د ستورپوهنې کارپوهنيز ډګرونه په دوه څانګو وېشل شوي. يو يې ليدنيزه ستورپوهنه او بل يې د نظري ستورپوهنې څانګې دي. ليدنيزه ستورپوهنه د ډاټا په شننو او ترلاسه کولو ځيره ده چې په لويه کچه دا د فيزيک د بنسټيزو اصولو د کارولو په مرسته ترسره کېږي. نظري ستورپوهنه د کمپيوټري پرمختګ يا شننيزو مخبېلګو په مرسته د ستورپوهنيزو ځليزو او شيانو لورې رڼا اچوي. دا دوه ډګرونه يو بل سره بشپړوي، د نظري ستورپوهنې په مرسته د ليدنو پايلې او هغه ليدنې چې د نظري پايلو پخلی پرې کېږي ښه سره پېژندل کېږي.

د تاريخ له مخې، شوقي ستورپوهانو په اهمو ستورپوهنيزو لاسته راوړنو کې ډېره ونډه درلوده، او په همدې توګه ستورپوهنه يو د هغو لږو ساينسونو څخه دی په کوم کې چې لېواله ستورپوهان يو کوانده رول د ستورپوهنيزو توکو په پېژندنه کې لوبولی شي، په ځانګړې توګه د ټرانسينټ ځليزې (transient phenomena) په ليدنې او موندنې کې.

بايده چې د نوې ستورپوهنې او ستورپېژندنې تر مېنځ ټکني نه شو او د دغو ببېلابېلو ډګرونو تر مېنځ توپير وکړو. وروستی نومېدلی نوم، ستورپېژندنه د ګروهو (عقيدو) يو غونډال دی کوم چې د انساني چارو د پېژندلو ادعا او وړاندوینې د اسماني شيانو د موقعيت او د هغو د خپلمنځي اړيکو له ليدنو وروسته رامېنځ ته کېږي. که څه هم چې دا دوه پوهنې يو ګډ آر (اصل) لري، خو د دغو دواړو علمونو پوه اندي په دې باور دي چې دا دوه بېلابېلې پوهنې دي.^[1]

[سمادول] د كائناتو پېداېښت (لويه چاودنه) (بګ بېنګ)

د كائناتو د پېداېښت په اړه چې د ستورپېژندونكيو پوهانو كومه نظريه وړاندې كړې كومه چې نن د ټولو په نزد د منلو وړ ده، او هغه نظريه چې دا كائنات د يوې لوې چاودنې (بګ بېنګ) په نتيجه كې منځته راغلي. ددې نظريې تائيد تر څو پېړيو پورې د ستورپېژندونكيو پوهانو د تجربو او لرليدو څخه د لاسته راوړنو له پاېلو څخه هم ؤ. د لوى چاودنې نظريې سره سم دا كاېنات په لومړي سر كې د ناټاكلې شكل په لرلو سره د يوه ستر كاڼي (Primary Nebula) په څېر وه.

بيا د يوې سترې چاودنې (secondaray separation) په نتيجه كې كهكشانونه راپېدا شول. او دا كهكشانونه نور زيات ووېشل شول، چې لدې وېش څخه بيا ستورې، سيارې، لمر او سپوږمۍ راپېدا شول. د كاېناتو [[پېدېښت] په يوه ځانګړي او له [[عقل] څخه وتلي ډول سره شوې. ددې كاېناتو پېداېښت په خپلسرې ډول له شونياوو څخه وتلې. قرآن كريم د كاېناتو د پېداښت راز په داسې راښكاره كوي:

• • ژباړه: آيا كاپرانو پدې خبره غور او فكر ندې كړې چې (لومړې مو) اسمان او زمكه (سره) يو ځاى (نښتي) ول، بيا موږ سره جلا جلا كړل.( القرآن، ۳۰-۲۱)

د قرآن كريم ددې آيت او د لوې چاودنې د نظريې ترمنځ چې كوم همغږي او يوشانته والې ليدل كېږي د هغې رد په هېڅ ډول ناشونې دى. دا څرنګه كېداى شي چې ۱۴ پېړۍ مخكې د عربو په صحرا كې داسې يو كتاب بياموندل شي چې داسې يوه رېښتوني ساېنسي حقيقت پكې موجود وي.

[سمادول] د ګېس ستر غونډارې

د كهكشانو له پېداېښت څخه مخكې د ګېس يو ستر غونډارې: ستورپېژندونكي پدې ګروهه دي چې په كون د كهكشانونو منځته راتلو څخه مخكې دا كون ټول له سره د ګېس په څېر ول، يانې له كهكشانونو څخه مخكې دا كون د يوه ستر ګېسي غونډارو يا ورېځو په څېر ؤ. او يا ددې مادې لپاره د ګېس څخه د دوړو كلېمه استعمالول لږ څه ښه راځي، (يانې يوه غېر متشكله دوړو په څېر). د كون دې شكل ته قرآن كريم په لاندې آيت كې داسې اشاره كوي او د (دخان) كلېمه يې راوړې چې د دوړې يا دود په مانا راځي:

• • ژباړه: بيا هه د اسمان اړخ ته پام وړ، كوم چې په هغه وخت كې يوه دوړه وه. هغه اسمان او زمكې ته وويل: (موجود شئ، كه چېرې ستاسو غواړئ او يا نه غواړئ. دواړو وويل: موږ راغلو امر منونكيو په څېر). (القرآن، ۱۱-۴۱)

وګورئ قرآن كريم يو بل بيان د (بګ بېنګ) له نظريې سره يوشانوالې. آيا دا رېښتيا د محمد صلى الله عليه وسلم له پېداېښت څخه مخكې چاته مالوم ول؟ نو بيا ددې ستر ساېنسي حقيقت كومه بله ذريعه كېدا شي؟ (د بګ بېنګ نظريه د تېر نږدې وخت ده، خو قرآن كريم دا حقيقت ۱۴ پېړۍ مخكې بيان كړې دى.

[سمادول] د ستورو ترمنځ څه دي؟

په لومړي سر كې داسې ګومان كېده چې د منظمو فلكي نظامونو څخه اخوا خلا بېخي تشه ده، مګر نن سبا ساېنسي ستورپېژندونكي دې پاېلې ته ورسېدل چې د ستور ترمنځ داسې يوه ماده شته چې د پل (bridge) په څېر دى او دې مادې ته يې د پلازما نوم وركړ. دا ماده په بشپړ ډول سره اوسپنه كړاى شوې (ionized) ګېس لرونكې ده. پدې ماده كې په مساوي ډول منفي چارچ لرونكي خپلواك الكترونونه او مثبت چارچ لرونكي برقي پاڼې (Ions) موجودې دي. پلامزما ته كله كله د مادې څلورم حالت هم وايي. ( د مادې درې مشهور حالتونه دي: جامد، ماېع او ګېس). څښتن تعالى د قرآن كريم په لاندې آيت كې د ستورو ترمنځ تشه كې د موجودې مادې په اړه داسې فرمايي:

• • ژباړه: (هغه چا چې په ۶ ورځو كې زمكه او اسمان او هرهغه څه پېدا كړل، چې د اسمان او زمكې ترمنځ وي. القرآن، ۵۹-۲۵).

[سمادول] زمكه ګرده ده

له لومړيو وختو كې خلكو دا ګومان كاوه چې زمكه هوار ده، او ددې لپاره به يې د لرې واټن له سفر كولو څخه ځانونه ژغورل، چې نه چېرې د زمكې په ختمېدو سره د هغې له لمنو څخه لاندې ونه لوېږي. فرانسس ډرېك لومړنې كس ؤ چې په ۱۵۹۷زېږيز كال كې يې په بحري بېړۍ كې د زمكې ګردچاپېره سفر وكړ، او دا يې په زبات ورسوله چې زمكه په اصل كې ګرده ( كروي) ده.

[سمادول] وييپوهنه

ستورپوهنې ته په انګرېزي ژبه astronomy وايي او دا د ستورو قانون په مانا ده. همدا ويي په اصل کې د يوناني ژبې د وييکې αστρονομία, آسټرونوميا، نه راوتلې چې άστρον (آسټرون، يعنی "ستوری") او νόμος (نوموس، يعنی "د نومونو قانون") مانا لري.

[سمادول] د "ستورپوهنې" او "آسټروفيزيکس" د وييونو کارونه

په ټولګړي توګه، دواړه نومونه، هم د "آسټرونومي" او يا هم د "آسټروفيزيکس" اصطلاحګانې د ستورپوهنې د مضمون لور ته اشاره کوي.^[2][3][4] د يو کره سيند (قاموس) د پېژند له مخې، "ستورپوهنه" يا "آسټرونومي هغې پوهې ته وايي چې د زمکې د اتموسفير نه دباندې د مادې او نورو اسماني شيانو د کتنو او پېژندلو سره سره د هغوی د فيزيکي او کيميايي ځانګړتياو په هکله څېړنې او بحثونه کوي."^[5]او د "آسټروفيزيکس" کلمه "د ستورپوهنې هغې څانګې ته وايي کوم چې د فلکي شيانو او ځليزو (فېنامېنا) د فيزيکي ځانګړنو، خاصيتونه او د هغوی خوځنده کړنو په هکله څېړنې کوي او همدغو ځانګړنو پورې اړونده پوښتنو ته ځواب وايي."^[6] په ځينو ځاينو کې، لکه د فرانک شو د کتاب فيزيکي کاينات په پېژندګلوي کې راغلي چې، "ستورپوهنه" د يو موضوع د کيفيتي زده کړو په راپېژندلو کې کارېږي خو "آسټروفيزيکس" بيا پر فيزيک مبنا د يو موضوع د بڼې په پېژندنه کې کارېږي.^[7] However, since most modern astronomical research deals with subjects related to physics, modern astronomy could actually be called astrophysics.^[2] Various departments that research this subject may use "astronomy" and "astrophysics", partly depending on whether the department is historically affiliated with a physics department,^[3] and many professional astronomers actually have physics degrees.^[4] Even the name of the scientific journal Astronomy & Astrophysics reveals the ambiguity of the use of the term.

[سمادول] تاريخ

Main article: د ستورپوهنې تاريخ

کينډۍ:See

A celestial map from the 17th century, by the Dutch cartographer Frederik de Wit.

In early times, astronomy only comprised the observation and predictions of the motions of objects visible to the naked eye. In some locations, such as Stonehenge, early cultures assembled massive artifacts that likely had some astronomical purpose. In addition to their ceremonial uses, these observatories could be employed to determine the seasons, an important factor in knowing when to plant crops, as well as in understanding the length of the year.^[8]

Before tools such as the telescope were invented early study of the stars had to be conducted from the only vantage points available, namely tall buildings, trees and high ground using the bare eye.

As civilizations developed, most notably Mesopotamia, Egypt, Persia, Maya, Greece, India, and China, astronomical observatories were assembled, and ideas on the nature of the universe began to be explored. Early ideas about the motions of the planets were formed, and the nature of the Sun, Moon and the Earth in the universe were explored philosophically. The Earth was believed to be the center of the universe with the Sun, the Moon and the stars rotating around it. This is known as the geocentric model of the universe.

A few notable astronomical discoveries were made prior to the application of the telescope. For example, the obliquity of the ecliptic was estimated as early as 1,000 B.C by the Chinese. The Chaldeans discovered that eclipses recurred in a repeating cycle known as a saros.^{[citation needed]} In the second century B.C., the size and distance of the Moon were estimated by Hipparchus.

During the Middle Ages, observational astronomy was mostly stagnant in medieval Europe, at least until the 13th century. However, observational astronomy flourished in the Persian Empire and other parts of the world. Astronomers during that time introduced many names that are now used for individual stars.^[9][10]

[سمادول] پوهنيز بدلون

Galileo's sketches and observations of the Moon revealed that the surface was mountainous

During the Renaissance, Nicolaus Copernicus proposed a heliocentric model of the solar system. His work was defended, expanded upon, and corrected by Galileo Galilei and Johannes Kepler. Galileo innovated by using telescopes to enhance his observations.

Kepler was the first to devise a system that described correctly the details of the motion of the planets with the Sun at the center. However, Kepler did not succeed in formulating a theory behind the laws he wrote down. It was left to Newton's invention of celestial dynamics and his law of gravitation to finally explain the motions of the planets. Newton also developed the reflecting telescope.

Further discoveries paralleled the improvements in the size and quality of the telescope. More extensive star catalogues were produced by Lacaille. The astronomer William Herschel made a detailed catalog of nebulosity and clusters, and in 1781 discovered the planet Uranus, the first new planet found. The distance to a star was first announced in 1838 when the parallax of 61 Cygni was measured by Friedrich Bessel.

During the nineteenth century, attention to the three body problem by Euler, Clairaut, and D'Alembert led to more accurate predictions about the motions of the Moon and planets. This work was further refined by Lagrange and Laplace, allowing the masses of the planets and moons to be estimated from their perturbations.

Significant advances in astronomy came about with the introduction of new technology, including the spectroscope and photography. Fraunhofer discovered about 600 bands in the spectrum of the Sun in 1814-15, which, in 1859, Kirchhoff ascribed to the presence of different elements. Stars were proven to be similar to the Earth's own Sun, but with a wide range of temperatures, masses, and sizes.^[9]

The existence of the Earth's galaxy, the Milky Way, as a separate group of stars, was only proved in the 20th century, along with the existence of "external" galaxies, and soon after, the expansion of the universe, seen in the recession of most galaxies from us. Modern astronomy has also discovered many exotic objects such as quasars, pulsars, blazars, and radio galaxies, and has used these observations to develop physical theories which describe some of these objects in terms of equally exotic objects such as black holes and neutron stars. Physical cosmology made huge advances during the 20th century, with the model of the Big Bang heavily supported by the evidence provided by astronomy and physics, such as the cosmic microwave background radiation, Hubble's law, and cosmological abundances of elements.

[سمادول] ستورپوهنيزې کتنې

Radio telescopes are among the many different tools used by astronomers

In Babylon and ancient Greece, astronomy consisted largely of astrometry, measuring the positions of stars and planets in the sky. Later, the work of astronomers Kepler and Newton led to the development of celestial mechanics, and astronomy focused on mathematically predicting the motions of gravitationally interacting celestial bodies. This was applied to solar system objects in particular. Today, the motions and positions of objects are more easily determined, and modern astronomy concentrates on observing and understanding the physical nature of celestial objects.

[سمادول] د مالوماتو د راغونډولو چلندلار

Main article: Observational astronomy

In astronomy, information is mainly received from the detection and analysis of light and other forms of electromagnetic radiation.^[11] However, useful information has also been acquired using neutrino detectors. These have been used to observe solar neutrinos, and neutrino emissions from supernovae have also been detected. There are also instruments to observe the effects of cosmic rays, and, in the near future, several experiments are designed to detect gravitational waves.^[12]

A traditional division among astronomy fields is based on the region of the electromagnetic spectrum observed. At the low frequency end of the spectrum, radio astronomy detects radiation in wavelengths measuring between a millimeter and a dekameter. The radio telescope receivers are similar to those used in radio broadcast transmissions, but are much more sensitive. Microwaves form the millimeter end of the radio spectrum, and are important for studies of the cosmic microwave background radiation.

Infrared astronomy and far infrared astronomy deal with the detection and analysis of infrared radiation (wavelengths longer than red light). The most common instrument used to isolate this band is a telescope that uses a detector which is sensitive to the infrared. Infrared radiation is heavily absorbed by atmospheric water vapor, so infrared observatories have to be located in high, dry places or in outer space. Space telescopes in particular avoid atmospheric thermal emissions, atmospheric opacity, and the negative effects of astronomical seeing at infrared and other wavelengths. Infrared is particularly useful for observation of galactic regions cloaked by dust, and for studies of molecular gases.

Because of the altitude and isolation, the Mauna Kea Observatory has some of the best observing conditions on Earth

Historically, most astronomical data has been collected through optical astronomy. This is the portion of the spectrum that uses optical components (mirrors, lenses, CCD detectors and photographic films) to observe light from near infrared to near ultraviolet wavelengths. Visible light astronomy (using wavelengths that can be detected with the eyes, about 400–700 nm) falls in the middle of this range. The most common instrument is the telescope, with electronic imagers and spectrographs.

More energetic sources are observed and studied in high-energy astronomy, which includes X-ray astronomy, gamma ray astronomy, and extreme UV (ultraviolet) astronomy, as well as the studies of neutrinos and cosmic rays.

Optical and radio astronomy can be performed with ground-based observatories, because the Earth's atmosphere is transparent at the wavelengths being detected. The atmosphere is opaque at the wavelengths of X-ray astronomy, gamma-ray astronomy, UV astronomy, and (except for a few wavelength "windows") far infrared astronomy, so observations must be carried out mostly from balloons or space observatories. Powerful gamma rays can, however, be detected by the large air showers that they produce; and the study of cosmic rays can also be regarded as a branch of astronomy.^[13]

Planetary astronomy has benefited from direct observation in the form of spacecraft and sample return missions. These include fly-by missions with remote sensors; landing vehicles that can perform experiments on the surface materials; impactors that allow remote sensing of buried material, and sample return missions that allow direct, laboratory examination.

[سمادول] ستورپوهنه او اسماني تخنيکونه

Main article: Astrometry

One of the oldest fields in astronomy, and in all of science, is the measurement of the positions of celestial objects. Historically, accurate knowledge of the positions of the Sun, Moon, planets and stars has been essential in celestial navigation.

Careful measurement of the positions of the planets has led to a solid understanding of gravitational perturbations, and an ability to determine past and future positions of the planets with great accuracy, a field known as celestial mechanics. More recently the tracking of near-Earth objects will allow for predictions of close encounters, and potential collisions, with the Earth.^[14]

The measurement of stellar parallax of nearby stars provides a fundamental baseline in the cosmic distance ladder that is used to measure the scale of the universe. Parallax measurements of nearby stars provide an absolute baseline for the properties of more distant stars, because their properties can be compared. Measurements of radial velocity and proper motion show the kinematics of these systems through the Milky Way galaxy. Astrometric results are also used to measure the distribution of dark matter in the galaxy.^[15]

During the 1990s, the astrometric technique of measuring the stellar wobble was used to detect large extrasolar planets orbiting nearby stars.^[16]

[سمادول] د ستورپوهنې څانګې

Astronomy may be divided into several subfields depending on the approach used in research, the part of the electromagnetic spectrum used for for study, or the types of astronomical objects being studied.

[سمادول] Subfields for specific parts of the electromagnetic spectrum

[سمادول] راډيو ستورپوهنه

Radio astronomy studies radiation with wavelengths greater than approximately one millimeter.^[17] Radio astronomy is different from most other forms of observational astronomy in that the observed radio waves can be treated as waves rather than as discrete photons. Hence, it is relatively easier to measure both the amplitude and phase of radio waves, whereas this is not as easily done at shorter wavelengths.^[17]

Although some radio waves are produced by astronomical objects in the form of thermal emission, most of the radio emission that is observed from Earth is seem in the form of synchrotron radiation, which is produced when electrons oscillate around magnetic fields.^[17] Additionally, a number of spectral lines produced by interstellar gas, particularly the hydrogen spectral line at 21 cm, are observable at radio wavelengths.^[7][17]

A wide variety of objects are observable at radio wavelengths, including supernovae, interstellar gas, pulsars, and active galactic nuclei.^[7][17]

[سمادول] Infrared astronomy

Infrared astronomy studies radiation with a wavelength that is too long to be visible but shorter than radio waves. Infrared observations are usually made with telescopes similar to the usual optical telescopes. Objects colder than stars (such as planets) are normally studied at infrared frequencies.

[سمادول] Optical astronomy

Optical astronomy is the oldest kind of astronomy. Telescopes paired with a charge-coupled device or spectroscopes are the most common instruments used. The Earth's atmosphere interferes somewhat with optical observations, so adaptive optics and space telescopes are used to obtain the highest possible image quality. In this range, stars are highly visible, and many chemical spectra can be observed to study the chemical composition of stars, galaxies and nebulae.

[سمادول] Ultraviolet astronomy

Ultraviolet astronomy is generally used to refer to observations at ultraviolet wavelengths between approximately 100 and 3200 Å.^[17] Light at these wavelengths is absorbed by the Earth's atmosphere, so observations at these wavelengths must be performed from the upper atmosphere or from space. Ultraviolet astronomy is best suited to the study of thermal radiation and spectral emission lines from hot blue stars (O stars and B stars) that are very bright in this wave band. This includes the blue stars in other galaxies, which have been the targets of several ultraviolet surveys. Other objects commonly observed in ultraviolet light include planetary nebulae, supernova remnants, and active galactic nuclei.^[17] However, ultraviolet light is easily absorbed by interstellar dust, and measurement of the ultraviolet light from objects need to be corrected for extinction.^[17]

[سمادول] د اکس وړانګې ستورپوهنه

X-ray astronomy is the study of astronomical objects at X-ray wavelengths. Typically, objects emit X-ray radiation as synchrotron emission (produced by electrons oscillating around magnetic field lines), thermal emission from thin gases (called bremsstrahlung radiation) that is above 10⁷ (10 million) Kelvin, and thermal emission from thick gases (called blackbody radiation) that are above 10⁷ Kelvin.^[17] Since X-rays are absorbed by the Earth's atmosphere, all X-ray observations must be done from high-altitude balloons, rockets, or spacecraft.^{[citation needed]} Notable X-ray sources include X-ray binaries, pulsars, supernova remnants, elliptical galaxies, clusters of galaxies, and active galactic nuclei.^[17]

[سمادول] د ګاما وړانګې ستورپوهنه

Gamma ray astronomy is the study of astronomical objects at the shortest wavelengths of the electromagnetic spectrum. Gamma rays may be observed directly by satellites such as the Compton Gamma Ray Observatory or by specialized telescopes called atmospheric Cherenkov telescopes.^[17] The Cherenkov telescopes do not actually detect the gamma rays directly but instead detect the flashes of visible light produced when gamma rays are absorbed by the Earth's atmosphere.^{[citation needed]}

Most gamma-ray emitting sources are actually gamma-ray bursts, objects which only produce gamma radiation for a few milliseconds to thousands of seconds before fading away. Only 10% of gamma-ray sources are non-transient sources. These steady gamma-ray emitters include pulsars, neutron stars, and black hole candidates such as active galactic nuclei.^[17]

[سمادول] Fields of observational astronomy not based on the electromagnetic spectrum

Other than electromagnetic radiation, few things may be observed from the Earth that originate from great distances.

In neutrino astronomy, astronomers use special underground facilities such as SAGE, GALLEX, and Kamioka II/III for detecting neutrinos. These neutrinos originate primarily from the Sun but also from supernovae.^[17]

Cosmic rays consisting of very high energy particles can be observed hitting the Earth's atmosphere.کينډۍ:Citation needed Additionally, some future neutrino detectors will also be sensitive to the neutrinos produced when cosmic rays hit the Earth's atmosphere.^[17]

A few gravitational wave observatories have been constructed, but gravitational waves are extremely difficult to detect.

[سمادول] Subfield for specific astronomical objects

[سمادول] لمريزه ستورپوهنه

Main article: لمر

The most frequently studied star is the Sun, a typical main-sequence dwarf star of stellar class G2 V, and about 4.6 Gyr in age. The Sun is not considered a variable star, but it does undergo periodic changes in activity known as the sunspot cycle. This is an 11-year fluctuation in sunspot numbers. Sunspots are regions of lower-than- average temperatures that are associated with intense magnetic activity.^[18]

An ultraviolet image of the Sun's active photosphere as viewed by the TRACE space telescope. NASA photo.

The Sun has steadily increased in luminosity over the course of its life, increasing by 40% since it first became a main-sequence star. The Sun has also undergone periodic changes in luminosity that can have a significant impact on the Earth.^[19] The Maunder minimum, for example, is believed to have caused the Little Ice Age phenomenon during the Middle Ages.^[20]

The visible outer surface of the Sun is called the photosphere. Above this layer is a thin region known as the chromosphere. This is surrounded by a transition region of rapidly increasing temperatures, then by the super-heated corona.

At the center of the Sun is the core region, a volume of sufficient temperature and pressure for nuclear fusion to occur. Above the core is the radiation zone, where the plasma conveys the energy flux by means of radiation. The outer layers form a convection zone where the gas material transports energy primarily through physical displacement of the gas. It is believed that this convection zone creates the magnetic activity that generates sun spots.^[18]

A solar wind of plasma particles constantly streams outward from the Sun until it reaches the heliopause. This solar wind interacts with the magnetosphere of the Earth to create the Van Allen radiation belts, as well as the aurora where the lines of the Earth's magnetic field descend into the atmosphere.^[21]

[سمادول] Planetary science

Main article: Planetary science

This astronomical field examines the assemblage of planets, moons, dwarf planets, comets, asteroids, and other bodies orbiting the Sun, as well as extrasolar planets. The solar system has been relatively well-studied, initially through telescopes and then later by spacecraft. This has provided a good overall understanding of the formation and evolution of this planetary system, although many new discoveries are still being made.^[22]

The black spot at the top is a dust devil climbing a crater wall on Mars. This moving, swirling column of Martian atmosphere (comparable to a terrestrial tornado) created the long, dark streak. NASA image.

The solar system is subdivided into the inner planets, the asteroid belt, and the outer planets. The inner terrestrial planets consist of Mercury, Venus, the Earth, and Mars. The outer gas giant planets are Jupiter, Saturn, Uranus and Neptune.^[23] Beyond Neptune lie the Kuiper Belt, and finally the Oort Cloud, which may extend as far as a light-year.

The planets were formed by a protoplanetary disk that surrounded the early Sun. Through a process that included gravitational attraction, collision, and accretion, the disk formed clumps of matter that, with time, became protoplanets. The radiation pressure of the solar wind then expelled most of the unaccreted matter, and only those planets with sufficient mass retained their gaseous atmosphere. The planets continued to sweep up, or eject, the remaining matter during a period of intense bombardment, evidenced by the many impact craters on the Moon. During this period, some of the protoplanets may have collided, the leading hypothesis for how the Moon was formed.^[24]

Once a planet reaches sufficient mass, the materials with different densities segregate within, during planetary differentiation. This process can form a stony or metallic core, surrounded by a mantle and an outer surface. The core may include solid and liquid regions, and some planetary cores generate their own magnetic field, which can protect their atmospheres from solar wind stripping.^[25]

A planet or moon's interior heat is produced from the collisions that created the body, radioactive materials (e.g. uranium, thorium, and ²⁶Al), or tidal heating. Some planets and moons accumulate enough heat to drive geologic processes such as volcanism and tectonics. Those that accumulate or retain an atmosphere can also undergo surface erosion from wind or water. Smaller bodies, without tidal heating, cool more quickly; and their geological activity ceases with the exception of impact cratering.^[26]

[سمادول] Stellar astronomy

Main article: Star

The study of stars and stellar evolution is fundamental to our understanding of the universe. The astrophysics of stars has been determined through observation and theoretical understanding; and from computer simulations of the interior.

Star formation occurs in dense regions of dust and gas, known as giant molecular clouds. When destabilized, cloud fragments can collapse under the influence of gravity, to form a protostar. A sufficiently dense, and hot, core region will trigger nuclear fusion, thus creating a main-sequence star.^[27]

The characteristics of the resulting star depend primarily upon its starting mass. The more massive the star, the greater its luminosity, and the more rapidly it expends the hydrogen fuel in its core. Over time, this hydrogen fuel is completely converted into helium, and the star begins to evolve. The fusion of helium requires a higher core temperature, so that the star both expands in size, and increases in core density. The resulting red giant enjoys a brief life span, before the helium fuel is in turn consumed. Very massive stars can also undergo a series of decreasing evolutionary phases, as they fuse increasingly heavier elements.

The final fate of the star depends on its mass, with stars of mass greater than about eight times the Sun becoming core collapse supernovae; while smaller stars form planetary nebulae, and evolve into white dwarfs. The remnant of a supernova is a dense neutron star, or, if the stellar mass was at least three times that of the Sun, a black hole.^[28] Close binary stars can follow more complex evolutionary paths, such as mass transfer onto a white dwarf companion that can potentially cause a supernova.

[سمادول] کهکشاني ستورپوهنه

Main article: Galactic astronomy

Observed structure of the Milky Way's spiral arms

Our solar system orbits within the Milky Way, a barred spiral galaxy that is a prominent member of the Local Group of galaxies. It is a rotating mass of gas, dust, stars and other objects, held together by mutual gravitational attraction. As the Earth is located within the dusty outer arms, there are large portions of the Milky Way that are obscured from view.

In the center of the Milky Way is the core, a bar-shaped bulge with what is believed to be a supermassive black hole at the center. This is surrounded by four primary arms that spiral from the core. This is a region of active star formation that contains many younger, population II stars. The disk is surrounded by a spheroid halo of older, population I stars, as well as relatively dense concentrations of stars known as globular clusters.^[29][30]

Between the stars lies the interstellar medium, a region of sparse matter. In the densest regions, molecular clouds of molecular hydrogen and other elements create star-forming regions. These begin as irregular dark nebulae, which concentrate and collapse (in volumes determined by the Jeans length) to form compact protostars.^[31]

As the more massive stars appear, they transform the cloud into an H II region of glowing gas and plasma. The stellar wind and supernova explosions from these stars eventually serve to disperse the cloud, often leaving behind one or more young open clusters of stars. These clusters gradually disperse, and the stars join the population of the Milky Way.

Kinematic studies of matter in the Milky Way and other galaxies have demonstrated that there is more mass than can be accounted for by visible matter. A dark matter halo appears to dominate the mass, although the nature of this dark matter remains undetermined.^[32]

[سمادول] Extragalactic astronomy

Main article: Extragalactic astronomy

The study of objects outside of our galaxy is a branch of astronomy concerned with the formation and evolution of Galaxies; their morphology and classification; and the examination of active galaxies, and the groups and clusters of galaxies. The latter is important for the understanding of the large-scale structure of the cosmos.

This image shows several blue, loop-shaped objects that are multiple images of the same galaxy, duplicated by the gravitational lens effect of the cluster of yellow galaxies near the middle of the photograph. The lens is produced by the cluster's gravitational field that bends light to magnify and distort the image of a more distant object.

Most galaxies are organized into distinct shapes that allow for classification schemes. They are commonly divided into spiral, elliptical and Irregular galaxies.^[33]

As the name suggests, an elliptical galaxy has the cross-sectional shape of an ellipse. The stars move along random orbits with no preferred direction. These galaxies contain little or no interstellar dust; few star-forming regions; and generally older stars. Elliptical galaxies are more commonly found at the core of galactic clusters, and may be formed through mergers of large galaxies.

A spiral galaxy is organized into a flat, rotating disk, usually with a prominent bulge or bar at the center, and trailing bright arms that spiral outward. The arms are dusty regions of star formation where massive young stars produce a blue tint. Spiral galaxies are typically surrounded by a halo of older stars. Both the Milky Way and the Andromeda Galaxy are spiral galaxies.

Irregular galaxies are chaotic in appearance, and are neither spiral nor elliptical. About a quarter of all galaxies are irregular, and the peculiar shapes of such galaxies may be the result of gravitational interaction.

An active galaxy is a formation that is emitting a significant amount of its energy from a source other than stars, dust and gas; and is powered by a compact region at the core, usually thought to be a super-massive black hole that is emitting radiation from in-falling material.

A radio galaxy is an active galaxy that is very luminous in the radio portion of the spectrum, and is emitting immense plumes or lobes of gas. Active galaxies that emit high-energy radiation include Seyfert galaxies, Quasars, and Blazars. Quasars are believed to be the most consistently luminous objects in the known universe.^[34]

The large-scale structure of the cosmos is represented by groups and clusters of galaxies. This structure is organized in a hierarchy of groupings, with the largest being the superclusters. The collective matter is formed into filaments and walls, leaving large voids in between.^[35]

[سمادول] Cosmology

Main article: Physical cosmology

Cosmology could be considered the study of the universe as a whole.

Observations of the large-scale structure of the universe, a branch known as physical cosmology, have provided a deep understanding of the formation and evolution of the cosmos. Fundamental to modern cosmology is the well-accepted theory of the big bang, wherein our universe began at a single point in time, and thereafter expanded over the course of 13.7 Gyr to its present condition. The concept of the big bang can be traced back to the discovery of the microwave background radiation in 1965.

In the course of this expansion, the universe underwent several evolutionary stages. In the very early moments, it is theorized that the universe experienced a very rapid cosmic inflation, which homogenized the starting conditions. Thereafter, nucleosynthesis produced the elemental abundance of the early universe.

When the first atoms formed, space became transparent to radiation, releasing the energy viewed today as the microwave background radiation. The expanding universe then underwent a dark age due to the lack of stellar energy sources.^[36]

A hierarchical structure of matter began to form from minute variations in the mass density. Matter accumulated in the densest regions, forming clouds of gas and the earliest stars. These massive stars triggered the reionization process and are believed to have created many of the heavy elements in the early universe.

Gravitational aggregations clustered into filaments, leaving voids in the gaps. Gradually, organizations of gas and dust merged to form the first primitive galaxies. Over time, these pulled in more matter, and were often organized into groups and clusters of galaxies, then into larger-scale superclusters.^[37]

Fundamental to the structure of the universe is the existence of dark matter and dark energy. These are now thought to be the dominant components, forming 96% of the density of the universe. For this reason, much effort is expended in trying to understand the physics of these components.^[38]

[سمادول] Interdisciplinary studies

کينډۍ:Seealso Astronomy and astrophysics have developed significant interdisciplinary links with other major scientific fields. These include:

• Astrobiology: the study of the advent and evolution of biological systems in the universe.
• Archaeoastronomy: the study of ancient or traditional astronomies in their cultural context, utilizing archaeological and anthropological evidence.
• Astrochemistry: the study of the chemicals found in outer space, usually in molecular gas clouds, and their formation, interaction and destruction. As such, it represents an overlap of the disciplines of astronomy and chemistry.

[سمادول] Amateur astronomy

Main article: Amateur astronomy

Collectively, amateur astronomers observe a variety of celestial objects and phenomena sometimes with equipment that they build themselves. Common targets of amateur astronomers include the Moon, planets, stars, comets, meteor showers, and a variety of deep-sky objects such as star clusters, galaxies, and nebulae. One branch of amateur astronomy, amateur astrophotography, involves the taking of photos of the night sky. Many amateurs like to specialize in the observation of particular objects, types of objects, or types of events which interest them.^[39][40]

Most amateurs work at visible wavelengths, but a small minority experiment with wavelengths outside the visible spectrum. This includes the use of infrared filters on conventional telescopes, and also the use of radio telescopes. The pioneer of amateur radio astronomy was Karl Jansky who started observing the sky at radio wavelengths in the 1930s. A number of amateur astronomers use either homemade telescopes or use radio telescopes which were originally built for astronomy research but which are now available to amateurs (e.g. the One-Mile Telescope).^[41][42]

Amateur astronomers continue to make scientific contributions to the field of astronomy. Indeed, it is one of the few scientific disciplines where amateurs can still make significant contributions. Amateurs can make occultation measurements that are used to refine the orbits of minor planets. They can also discover comets, and perform regular observations of variable stars. Improvements in digital technology have allowed amateurs to make impressive advances in the field of astrophotography. ^[43][44][45]

[سمادول] په ستورپوهنه کې لويې پوښتنې

کينډۍ:Seealso Although the scientific discipline of astronomy has made tremendous strides in understanding the nature of the universe and its contents, there remain some important unanswered questions. Answers to these may require the construction of new ground- and space-based instruments, and possibly new developments in theoretical and experimental physics.

• What is the origin of the stellar mass spectrum? That is, why do astronomers observe the same distribution of stellar masses—the initial mass function—apparently regardless of the initial conditions?^[46] A deeper understanding of the formation of stars and planets is needed.
• Is there other life in the Universe? Especially, is there other intelligent life? If so, what is the explanation for the Fermi paradox? The existence of life elsewhere has important scientific and philosophical implications.^[47][48]
• What is the nature of dark matter and dark energy? These dominate the evolution and fate of the cosmos, yet we are still uncertain about their true natures.^[49]
• Why did the universe come to be? Why, for example, are the physical constants so finely tuned that they permit the existence of life? Could they be the result of cosmological natural selection? What caused the cosmic inflation that produced our homogeneous universe?^[50]
• What will be the ultimate fate of the universe?^[51]

[سمادول] دا هم وګورۍ

کينډۍ:Wikiversity

[سمادول] لړليکونه

• List of basic astronomy topics
• List of astronomy topics
• List of ancient astronomy topics
• List of astronomical observatories
• List of astronomy organisations
• Astronomy timelines

[سمادول] اړونده ليکنې

• Astrology and astronomy
• Astronomer
• Cosmogony
• International Year of Astronomy
• Space exploration
• Space science

[سمادول] اخځليكونه

1. اردو وېكيپېډيا
2. طبعي جغرافيه، پروفېسر رياست علي عباسي، پاكستان بك سنټر- اردو بازار لاهور.
3. the Quran & Modern Science (compatible or Incompatible), by Dr. Zakir Naik, beacon books Qazafi market Urdu Bazar, Lahore, Ph: 0427351662

[سمادول] سرچينې

[سمادول] باندنۍ تړنې

کينډۍ:Sisterlinks

• International Year of Astronomy 2009 IYA2009 Main website
• Cosmic Journey: A History of Scientific Cosmology from the American Institute of Physics
• Astronomy Picture of the Day
• Southern Hemisphere Astronomy
• Sky & Telescope publishers
• Astronomy Magazine
• Latest astronomy news in 11 languages
• Universe Today for astronomy and space-related news
• Search Engine for Astronomy
• Hubblesite.org - home of NASA's Hubble Space Telescope
• The New Student's Reference Work/Astronomy (historical)
• Cosmic Journey: A History of Scientific Cosmology from the American Institute of Physics
• Prof. Sir Harry Kroto, NL, Astrophysical Chemistry Lecture Series. 8 Freeview Lectures provided by the Vega Science Trust.

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