Science fiction writers have long featured terraforming, the process of creating an Earth-like or habitable environment on another planet, in their stories. Scientists themselves have proposed terraforming to enable the long-term In an international collaboration between Japan and Sweden, scientists clarified how gravity affects the shape of matter near the black hole in binary system Cygnus X Their findings, which were published in Nature Astronomy Sep 13, in Astronomy Sep 17, in Astronomy 1. Sep 10, in Astronomy 2.
Aug 28, in Astronomy 3. Sep 04, in Astronomy 1. Aug 21, in Astronomy 0. Aug 27, in Space Exploration 0. Jul 30, in Astronomy 0. Jul 30, in Space Exploration During the s, the measurement of the stellar wobble of nearby stars was used to detect large extrasolar planets orbiting those stars.
Theoretical astronomers use several tools including analytical models and computational numerical simulations ; each has its particular advantages. Analytical models of a process are generally better for giving broader insight into the heart of what is going on. Numerical models reveal the existence of phenomena and effects otherwise unobserved. Theorists in astronomy endeavor to create theoretical models and from the results predict observational consequences of those models.
The observation of a phenomenon predicted by a model allows astronomers to select between several alternate or conflicting models as the one best able to describe the phenomena. Theorists also try to generate or modify models to take into account new data.
In the case of an inconsistency between the data and model's results, the general tendency is to try to make minimal modifications to the model so that it produces results that fit the data. In some cases, a large amount of inconsistent data over time may lead to total abandonment of a model. Phenomena modeled by theoretical astronomers include: Astrophysical relativity serves as a tool to gauge the properties of large scale structures for which gravitation plays a significant role in physical phenomena investigated and as the basis for black hole astro physics and the study of gravitational waves.
Some widely accepted and studied theories and models in astronomy, now included in the Lambda-CDM model are the Big Bang , Cosmic inflation , dark matter , and fundamental theories of physics. Dark matter and dark energy are the current leading topics in astronomy,  as their discovery and controversy originated during the study of the galaxies. At a distance of about eight light-minutes, the most frequently studied star is the Sun , a typical main-sequence dwarf star of stellar class G2 V, and about 4. The Sun is not considered a variable star , but it does undergo periodic changes in activity known as the sunspot cycle.
This is an year oscillation in sunspot number. Sunspots are regions of lower-than- average temperatures that are associated with intense magnetic activity. The Sun has also undergone periodic changes in luminosity that can have a significant impact on the Earth. 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, and finally 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. Above that is the convection zone where the gas material transports energy primarily through physical displacement of the gas known as convection. It is believed that the movement of mass within the convection zone creates the magnetic activity that generates sunspots. A solar wind of plasma particles constantly streams outward from the Sun until, at the outermost limit of the Solar System, it reaches the heliopause.
As the solar wind passes the Earth, it interacts with the Earth's magnetic field magnetosphere and deflects the solar wind, but traps some creating the Van Allen radiation belts that envelop the Earth. The aurora are created when solar wind particles are guided by the magnetic flux lines into the Earth's polar regions where the lines the descend into the atmosphere. Planetary science is the study of 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. The Solar System is subdivided into the inner planets, the asteroid belt , and the outer planets.
The inner terrestrial planets consist of Mercury , Venus , Earth , and Mars. The outer gas giant planets are Jupiter , Saturn , Uranus , and Neptune. The planets were formed 4. 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 and one such collision may have formed the Moon. Once a planet reaches sufficient mass, the materials of different densities segregate within, during planetary differentiation. This process can form a stony or metallic core, surrounded by a mantle and an outer crust. 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.
A planet or moon's interior heat is produced from the collisions that created the body, by the decay of radioactive materials e. 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. 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. 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. Almost all elements heavier than hydrogen and helium were created inside the cores of stars. 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 fuses its hydrogen fuel into helium 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. A star with a high enough core temperature will push its outer layers outward while increasing its core density. The resulting red giant formed by the expanding outer layers enjoys a brief life span, before the helium fuel in the core is in turn consumed. Very massive stars can also undergo a series of 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 blow off their outer layers and leave behind the inert core in the form of a white dwarf. The ejection of the outer layers forms a planetary nebula.
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 its 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 I stars. The disk is surrounded by a spheroid halo of older, population II stars, as well as relatively dense concentrations of stars known as globular clusters. 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 a compact pre-stellar core or dark nebulae , which concentrate and collapse in volumes determined by the Jeans length to form compact protostars. As the more massive stars appear, they transform the cloud into an H II region ionized atomic hydrogen of glowing gas and plasma. The stellar wind and supernova explosions from these stars eventually cause the cloud to disperse, 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. The study of objects outside our galaxy is a branch of astronomy concerned with the formation and evolution of Galaxies , their morphology description and classification , the observation of active galaxies , and at a larger scale, the groups and clusters of galaxies.
Finally, the latter is important for the understanding of the large-scale structure of the cosmos. Most galaxies are organized into distinct shapes that allow for classification schemes. They are commonly divided into spiral , elliptical and Irregular galaxies. 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 have been 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 within which massive young stars produce a blue tint. Spiral galaxies are typically surrounded by a halo of older stars. Both the Milky Way and one of our nearest galaxy neighbors, 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 emits a significant amount of its energy from a source other than its stars, dust and gas.
Nature Astronomy publishes research, reviews and commentary of the global efforts to introduce and develop astronomy and space science in areas. Astronomy and astrophysics are the study of objects and phenomena that are . awarded 50 years after the discovery — on increasing diversity in science.
It is powered by a compact region at the core, 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 shorter frequency, high-energy radiation include Seyfert galaxies , Quasars , and Blazars. Quasars are believed to be the most consistently luminous objects in the known universe. The large-scale structure of the cosmos is represented by groups and clusters of galaxies. This structure is organized into a hierarchy of groupings, with the largest being the superclusters. The collective matter is formed into filaments and walls, leaving large voids between.
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 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 neutral atoms formed from a sea of primordial ions, 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. A hierarchical structure of matter began to form from minute variations in the mass density of space.
Matter accumulated in the densest regions, forming clouds of gas and the earliest stars, the Population III stars. These massive stars triggered the reionization process and are believed to have created many of the heavy elements in the early Universe, which, through nuclear decay, create lighter elements, allowing the cycle of nucleosynthesis to continue longer.
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. Fundamental to the structure of the Universe is the existence of dark matter and dark energy. For this reason, much effort is expended in trying to understand the physics of these components.
Astronomy and astrophysics have developed significant interdisciplinary links with other major scientific fields. Archaeoastronomy is the study of ancient or traditional astronomies in their cultural context, utilizing archaeological and anthropological evidence. Astrobiology is the study of the advent and evolution of biological systems in the Universe, with particular emphasis on the possibility of non-terrestrial life.
Astrostatistics is the application of statistics to astrophysics to the analysis of vast amount of observational astrophysical data. The study of chemicals found in space, including their formation, interaction and destruction, is called astrochemistry. These substances are usually found in molecular clouds , although they may also appear in low temperature stars, brown dwarfs and planets.
Cosmochemistry is the study of the chemicals found within the Solar System, including the origins of the elements and variations in the isotope ratios. Both of these fields represent an overlap of the disciplines of astronomy and chemistry. As " forensic astronomy ", finally, methods from astronomy have been used to solve problems of law and history. Astronomy is one of the sciences to which amateurs can contribute the most. 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 Sun, the Moon, planets, stars, comets, meteor showers , and a variety of deep-sky objects such as star clusters, galaxies, and nebulae.
Astronomy clubs are located throughout the world and many have programs to help their members set up and complete observational programs including those to observe all the objects in the Messier objects or Herschel catalogues of points of interest in the night sky. 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.
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 s. 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. Amateur astronomers continue to make scientific contributions to the field of astronomy and 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. 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. From Wikipedia, the free encyclopedia. This article is about the scientific study of celestial objects. For other uses, see Astronomy disambiguation. Not to be confused with astrology , the pseudoscience. Archaeoastronomy and List of astronomers.
Astrometry and Celestial mechanics.
Planetary science and Planetary geology. Human timeline and Life timeline. List of unsolved problems in astronomy. Outline of astronomy and Glossary of astronomy. The Infinite Frontier television series. Classical Astronomy and the Solar System — Introduction. Classical Astronomy and the Solar System. An Introduction to Astronomy and Astrophysics.
Translated by Brewer, W. What is the difference between astronomy and astrophysics? Archived from the original on 9 June Retrieved 17 November Archived from the original on 8 July Retrieved 20 June Archived from the original on 1 November Archived from the original on 17 June An Introduction to the History and Philosophy of Science. Philosophical Transactions of the Royal Society. Archived from the original on 30 October Retrieved 28 October In Cancik, Hubert; Schneider, Helmuth.
Greek and Arabic Texts". Archive for History of Exact Sciences. Archived from the original on 23 October Encyclopedia of the History of Arabic Science. The Night Sky Observer's Guide. The Cambridge Concise History of Astronomy. The royal kingdoms of Ghana, Mali, and Songhay: Retrieved 3 February Archived from the original on 3 December Thebe; Urama, Johnson O.