The observable universe is a sphere of the universe composed of all matter observable from the Earth at this time, because the electromagnetic radiation of these objects has time to reach Earth from the very beginning of cosmological expansion.. There are at least 2 trillion galaxies in the observed universe. Assuming the isotropic universe, the distance to the edge of the observable universe is roughly the same in every direction. That is, the observed universe is the volume of the ball (ball) centered on the observer. Every location in the universe has an observable universe, which may or may not overlap with that centered on Earth.
The word can be observed in this sense does not refer to the ability of modern technology to detect light or other information from an object, or whether something is detectable. This refers to the physical boundary created by the speed of light itself. Since no signal can travel faster than light, any object farther away from us than light can travel at the age of the universe (estimated by 2015 around 13,799 Â ± 0.010 billion 0.021 billion year) can not be detected, because they have not contacted us yet. Sometimes astrophysicists distinguish between visible visible universes, which only include signals emitted since recombination - and the observable universe, which includes signals from the beginning of cosmological expansion (Big Bang) in traditional physical cosmology, the end of an era of inflation in modern cosmology).
According to calculations, the current approximate distance - the exact distance, which takes into account that the universe has evolved since the light is emitted - to the particles from which cosmic microwave background radiation (CMBR) is emitted, representing radius visible nature, about 14.0 billion parsec (about 45.7 billion light-years), while the approximate distance to the observed universe edge is about 14.3 billion parsecs (about 46.6 billion light-years), about 2% more big. The observable radius of the universe is estimated to be about 46.5 billion light-years and its diameter is about 28.5 gigaparsecs (93 billion light-years, 8.8 ÃÆ'- 10 23 kilometers or 5.5 ÃÆ' - 10 23 miles). The total mass of ordinary matter in the universe can be calculated using the critical density and diameter of the universe that can be observed to be about 1.5 Æ' 10 53 kg.
Since the expansion of the universe is known to accelerate and will become exponential in the future, the light emitted from all objects far beyond time depends on the current red shift will never reach Earth. In the future all the objects that can currently be observed will slowly freeze in time as the light emits fainter and fainter. For example, objects with a current redshift of z from 5 to 10 will remain observable for no more than 4-6 billion years. In addition, the light emitted by objects that are beyond a certain distance (currently around 19 billion parsecs) will never reach Earth.
Video Observable universe
Universe versus observable universe
Some parts of the universe are too far away for the light emitted since the Big Bang has enough time to reach Earth, and so be outside the observed universe. In the future, light from distant galaxies will have more time to travel, so additional territory will become observable. However, due to Hubble's law, a region far enough away from Earth extends far beyond that faster than the speed of light (special relativity prevents nearby objects in the same local area moving faster than the speed of light against each other, but there is no limit like that for distant objects when the space between them extends, see the use of the right distance for discussion) and furthermore the expansion rate seems to be accelerated due to dark energy. Assuming that dark energy remains constant (unchanged cosmological constant), so that the rate of expansion of the universe continues to accelerate, there is a "future visibility limit" beyond the object that will never enter the observable universe at any time in the infinite future, because the light emitted by objects beyond that limit will never reach Earth. (A subtlety is that, since the Hubble parameter decreases with time, there can be cases where galaxies are receding from Earth just a little faster than the light does emit signals that reach the Earth eventually.) The future visibility limit is calculated at a distance of close to 19 billion parsecs (62 billion light years), assuming the universe will continue to grow forever, implying the number of galaxies we can observe theoretically in the infinite future (excluding the problem that some may be impossible to observe in practice because of the redshift, as discussed in the following paragraph) is only greater than the amount currently observable by a factor of 2.36.
Although in principle more galaxies will be observable in the future, in practice more and more galaxies will become very redshifted due to ongoing expansion, so much so that they will appear to disappear from view and become invisible. An additional subtlety is that the galaxy at a specified distance is defined as being in the "observable universe" if we can receive signals emitted by the galaxy at any age in its past history (say, the signal sent from the galaxy is only 500 million years after Big Bang), but because of the expansion of the universe, there may be some later ages in which signals sent from the same galaxy can never reach the Earth at any point in the infinite future (so, for example , we may never see what looks like a galaxy 10 billion years after the Big Bang), although it remains at the same distance (close distance is defined constant with time - unlike the exact distance, used to determine the speed of recession due to space expansion), which is less than the approaching fingers of the observable universe. This fact can be used to determine the kind of cosmic event horizon whose distance from Earth changes over time. For example, the current distance to this horizon is about 16 billion light-years away, meaning that signals from current events can eventually reach Earth in the future if the event is less than 16 billion light-years, but the signal does not will ever reach Earth if it is more than 16 billion light years away.
Both popular and professional research articles in cosmology often use the term "universe" which means "observable universe". This can be justified on the grounds that we can never know anything by direct experimentation of any part of the universe indirectly cut off from Earth, although many credible theories require a universe far greater than the observed universe. There is no evidence to suggest that the observed boundary of the universe forms a boundary in the universe as a whole, nor is there a mainstream cosmological model that suggests that the universe has a physical boundary in the first place, although some models propose it. limited but unlimited, such as high-dimensional analogs of 2D surface balls that are finite in regions but have no edge. It is plausible that the galaxies in our observed universe represent only a small part of the galaxy in the universe. According to the cosmic inflation theory originally introduced by its founder, Alan Guth (and by D. Kazanas), if it is assumed that inflation starts about 10 -37 seconds after the Big Bang, then with reasonable assumption that the size of nature the universe before inflation occurs approximately equal to the speed of light times his age, which would indicate that at present the size of the entire universe is at least 3 Æ' â € "10 23 times the observable radius of the universe. There is also a lower estimate which claims that the entire universe is more than 250 times larger than the observed universe and also a higher estimate which implies that the universe is at least 10 10 10 122 times greater than the observed universe.
If the universe is finite but infinite, it is also possible that the universe is smaller than the observable universe. In this case, what we take to be a very distant galaxy may actually be a duplicate image of the nearest galaxy, formed by the light that surrounds the universe. It is difficult to test this hypothesis experimentally because different images of the galaxy will show a different era in its history, and the result may seem very different. Bielewicz et al. claims to set a lower limit of 27.9 gigaparsecs (91 billion light-years) on the last scattering surface diameter (since this is only the lower limit, the paper opens up the possibility that the entire universe is much larger, even infinitely). This value is based on a matching circle analysis of a 7-year WMAP data. This approach has been disputed.
Maps Observable universe
Size
The mileage from Earth to the edge of the observed universe is about 14.26 gigaparsecs (46.5 billion light-years or 4.40 ÃÆ' - 10 26 meters) in all directions. The observed universe thus is a sphere with a diameter of about 28.5 gigaparsecs (93Ã, Gly or 8.8 ÃÆ' - 10 26 m). Assuming the space is approximately flat (in Euclidean space sense), this size corresponds to the volume that follows it around 1.22 ÃÆ' - 10 4 G 3 ( 4,22 ÃÆ' - 10 5 Gly 3 or < span> 3.57 ÃÆ' - 10 80 m 3 ).
The numbers quoted above are the distance now (in cosmological time), not the distance when the light is emitted . For example, the cosmic microwave background radiation we see today is emitted at the time of photon release, estimated to have occurred around 380,000 years after the Big Bang, which occurred about 13.8 billion years ago. This radiation is emitted by matter which, at intervening time, is largely condensed into galaxies, and the galaxy is now calculated to be about 46 billion light-years away from us. To estimate the distance to that at which the light is emitted, we may first note that according to the Friedmann-LemaÃÆ'®tre-Robertson-Walker metric, used to model the expanding universe, if at present we receive light with a redshift z , then the scale factor at which the light was originally emitted was given by
.
The nine year WMAP results combined with other measurements provide redshift photon decoupling as z Ã, = Ã, 1 091 .64 Â ± 0 , 47 , which implies that the scale factor at the time of photon release is 1 / 1092.64 . So if the material emitting the oldest CMBR photon has a distance now of 46 billion light years, then at the time of separation when the photon is initially transmitted, the distance is only about 42 million euros > light years.
Misconception on its size
Many secondary sources have reported a variety of false numbers for the size of the visible universe. Some of these numbers are listed below, with brief descriptions of possible reasons for misunderstanding about them.
- 13.8 billion light years
- The age of the universe is estimated at 13.8 billion years. Although it is generally understood that nothing can speed up the same or greater speed than light, it is a common misconception that the observable radius of the universe should amount to only 13.8 billion light years. This reason would only make sense if the conception of Minkowski's flat and static spacetime under special relativity is true. In the real universe, the spacetime curves in a manner consistent with the expansion of space, as evidenced by Hubble's law. The distance obtained as the speed of light multiplied by the cosmological time interval has no direct physical significance.
- 15.8 billion light years
- This is obtained in the same way as the 13.8 billion light years, but from the age of the untrue universe reported in the popular press in mid 2006. For the analysis of this claim and the paper that triggered it, see the following references in the end of this article.
- 27.6 billion light years
- This is the diameter obtained from a (false) radius of 13.8 billion light years.
- 78 billion light-years
- In 2003, Cornish et al. find this lower limit for the diameter of the entire universe (not just the observable parts), postulate that the universe has a finite size because it has a nontrivial topology, with this lower limit based on the approximate range of current between the points we can see on the opposite side of cosmic microwave cosmic background (CMBR). If the entire universe is smaller than this sphere, then light has time to surround it since the Big Bang, generating many distant point shots in the CMBR, which will appear as a repeating circle pattern. Cornish et al. look for such effects on a scale of up to 24 gigaparsecs (78Ã, Gly or 7,4 ÃÆ' - 10 26 m) and fail to find it, and suggest that if they could expand their search for all possible orientations, they will then "be able to exclude the possibility that we are living in a universe smaller than 24 Gpc in diameter". The authors also estimate that with "low noise and high resolution CMB maps (from WMAP extended missions and from Planck), we will be able to look for smaller circles and extend the boundary to ~ 28 Gpc." The approximate maximum lower limit that can be determined by future observations corresponds to a radius of 14 gigaparsecs, or about 46 billion light-years, almost the same as the number for the visible universe radius (whose radius is determined by the CMBR sphere) is given in the opening section. Printed 2012 by most of the same authors as Cornish et al. paper has extended the current lower limit to a diameter of 98.5% CMBR ball diameter, or about 26 Gpc.
- 156 billion light years
- This figure is obtained by doubling 78 billion light-years on the assumption that it is a radius. Since 78 billion light years have become diameter (the original paper by Cornish et al.) Says, "By extending the search to all possible orientations, we will be able to exclude the possibility that we live in a universe smaller than 24 Gpc in diameter," and 24 Gpc is 78 billion light years), the number is doubly wrong. This number is very much reported. A press release from Montana State University-Bozeman, where Cornish works as an astrophysicist, noted a mistake when discussing a story that appeared in Discover magazine, saying " Discover it is mistakenly reported that the universe is 156 billion light-years away, thinking that 78 billion is the radius of the universe and not its diameter. "As mentioned above, 78 billion is also wrong.
- 180 billion light years
- This estimate combines the wrong 156 billion light years with evidence that the Galaxy M33 is actually fifteen percent farther than previously thought and that, therefore, the Hubble constant is fifteen percent smaller. The 180 billion figure is obtained by adding 15% to 156 billion light years.
Large-scale structure
Surveying the sky and mapping of various wavelengths of electromagnetic radiation (especially 21 cm emissions) has yielded much information about the contents and characters of the structure of the universe. Organization structures seem to follow as hierarchical models with organizations up to the scale of superclusters and filaments. Greater than this (on a scale between 30 and 200 megaparsecs), there seems to be no advanced structure, a phenomenon that has been referred to as the End of Greatness .
Wall, filament, vertex, and void
Organizational structures may start at the star level, although most cosmologists rarely discuss astrophysics on that scale. The stars are organized into galaxies, which in turn form clusters of galaxies, galaxy clusters, superclusters, sheets, walls and filaments, separated by large voids, creating large foam-like structures sometimes called "cosmic webs". Prior to 1989, it was generally assumed that virialized galactic clusters were the largest structures that existed, and that they were distributed more or less uniformly throughout the universe in every direction. However, since the early 1980s, more and more structures have been discovered. In 1983, Adrian Webster identified Webster LQG, a large quasar group consisting of five quasars. This discovery is the first identification of a large-scale structure, and has expanded information on the grouping of known matter in the universe. In 1987, Robert Brent Tully identified the Pisces-Cetus Supercluster Complex, the galactic filament where Milky Way was located. About 1 billion light years. That same year, an enormous area without a galaxy was discovered, the Giant Void, which measures 1.3 billion light-years. Based on red shift survey data, in 1989 Margaret Geller and John Huchra discovered the "Great Wall", a galaxy of over 500 million light years and 200 million light years, but only 15 million light-years thick. The existence of this structure escaped notice for so long because it requires placement of galaxy positions in three dimensions, involving the incorporation of location information about galaxies with distance information from redshifts. Two years later, astronomers Roger G. Clowes and Luis E. Campusano discovered Clowes-Campusano LQG, a large quasar group measuring two billion light-years at its widest point, the largest structure known in the universe at the time of its announcement.. In April 2003, another large-scale structure was discovered, the Great Wall of Sloan. In August 2007, a possible supervoid was detected in the Eridanus constellation. This coincides with the 'cold spot CMB', a cold region in the microwaved sky that is highly unlikely under the current preferred cosmological model. This supervoid can cause cold spots, but to do so must be very large, maybe a billion light years, almost as big as the Giant Giant mentioned above.
Another major structure is the Newfound Blob, a collection of galaxies and large gas bubbles that measure about 200 million light-years away.
In 2011, a large group of quasars was discovered, U1.11, measuring about 2.5 billion light-years away. On January 11, 2013, another large quasar group, Huge-LQG, was discovered, measured to four billion light-years, the largest structure known to the universe at that time. In November 2013, astronomers discovered the Great Wall of Hercules-Corona Borealis, a larger structure two times larger than before. It is defined by mapping gamma ray bursts.
End of Greatness
The End of Greatness is an observational scale found in about 100 Mpc (about 300 million light-years away) where the lumpiness seen in large-scale structures of the universe is homogenized and isotropized according to Cosmological Principles. On this scale, no apparent arbitrary fractality is apparent. Superclusters and filaments are seen in smaller surveys randomly to the extent that the subtle distribution of the universe is visually apparent. It was not until the 1990s redshift survey was completed that this scale could be accurately observed.
Observation
Another indicator of large-scale structures is 'Lyman-alpha forest'. It is a collection of absorption lines that appear in the light spectrum of quasars, which is interpreted as indicating the presence of large thin sheets of intergalactic gases (mostly hydrogen). These sheets seem to be related to the formation of new galaxies.
Care is needed in describing structures on a cosmic scale because things are often different from how they appear. Gravitational lensing (the curvature of light by gravity) can make the image appear to be coming from different directions from its original source. This is because when a foreground object (such as a galaxy) curves the surrounding space-time (as predicted by general relativity), and deflects light passes by. Instead of useful, powerful gravitational lensing can sometimes enlarge distant galaxies, making them easier to detect. Weak lensing (gravity shear) by the intervening universe in general also subtly alters the large-scale structures observed.
The large-scale structure of the universe also looks different if one only uses a redshift to measure the distance to the galaxy. For example, the galaxies behind the galaxy cluster are attracted to it, and so fall in its direction, and so are slightly blueshifted (compared to how they are if there is no cluster) On the near side, things are slightly redshifted. Thus, cluster environments look slightly oppressed if using redshifts to measure distances. The opposite effect works on existing galaxies in clusters: galaxies have random movements around the center of the cluster, and when this random movement is converted into redshift, the clusters appear elongated. This creates " the finger of God " - the illusion of a long chain of galaxies pointing to Earth.
Cosmography of Earth's cosmic environment
At the center of the Hydra-Centaurus Supercluster, a gravitational anomaly called Great Attractor affects the movement of galaxies over hundreds of millions of light-years. These galaxies are all redshift, in accordance with Hubble's law. It shows that they recede from us and from each other, but the variations in their red shift are sufficient to reveal the presence of mass concentrations equal to tens of thousands of galaxies.
The Great Attractor, discovered in 1986, lies at a distance between 150 million and 250 million light-years (250 million is the latest estimate), toward the constellations Hydra and Centaurus. In the vicinity there are many great old galaxies, many of whom collide with their neighbors, or emit radio waves in large numbers.
In 1987, astronomer R. Brent Tully of the Institute of Astronomy University of Hawaii identified what he called Pisces-Cetus Supercluster Complex, a billion light-years long and 150 million light-years in which, he said, The Local Supercluster is embedded.
Plain material mass
The observable mass of the universe is often quoted as 10 50 ton or 10 53 kg. In this context, mass refers to ordinary matter and includes interstellar medium (ISM) and intergalactic media (IGM). However, it does not include dark matter and dark energy. This quoted value for the ordinary matter mass in the universe can be estimated based on the critical density. The calculation is for the observed universe only because the whole volume is unknown and may be unlimited.
Estimates based on critical density
Critical density is the density of energy in which the universe is flat. If there is no dark energy, this is also the density in which the expansion of the universe lies between the continuing expansion and collapse. From the Friedmann equation, the value for Critical density, is:
where G is the gravitational constant and H 0 is the current value of the Hubble constant. The current value for H 0 , since the European Space Agency's Planck Telescope, is H 0 = 67.15 kilometers per second per mega parsec. This gives the critical density 0.85 ÃÆ' - 10 -26 kg/m 3 (usually quoted as about 5 hydrogen atoms per cubic meter). This density includes four significant types of energy/mass: ordinary matter (4.8%), neutrino (0.1%), dark dark matter (26.8%), and dark energy (68.3%). Note that although neutrinos are defined as particles such as electrons, they are listed separately because they are difficult to detect and very different from ordinary matter. The usual material density, as measured by Planck, is 4.8% of the total critical density or 4.08 ÃÆ' - 10 -28 kg/m 3 . To convert this density into mass, we must multiply the volume, the value based on the radius of the observable "universe". Since the universe has expanded over 13.8 billion years, the approximate distance (radius) is now about 46.6 billion light years away. So, the volume of <3 soup>) equals 3.58 ÃÆ' - 10 80 m 3 and the ordinary matter mass is equal to the density ( 4.08 ÃÆ' - 10 -28 Ã, kg/m 3 ) times the volume ( 3.58 ÃÆ' - 10 80 m 3 ) or 1,46 ÃÆ' - 10 < soup> 53 Ã, kg .
Material content - number of atoms
Assuming the ordinary matter mass is about 1.45 ÃÆ' - 10 53 Ã, kg (see previous section) and assuming all atoms are hydrogen atoms (which in fact constitute about 74% of all the atoms in our galaxy with mass, see Abundance of chemical elements), calculating the approximate total number of atoms in the observable universe is easy. Divide the mass of ordinary matter with the mass of the hydrogen atom ( 1,45 ÃÆ' - 10 53 Ã,kg divided by 1,67 ÃÆ' - 10 -27 Ã, kg ). The result is approximately 10 80 hydrogen atoms.
Most distant object
The most distant astronomical object that has not been announced in January 2011 is a galaxy candidate belonging to UDFj-39546284. In 2009, the gamma-ray burst, GRB 090423, was found to have redshift 8.2, indicating that the collapsed star caused it to explode when the universe was only 630 million years old. The explosion occurred about 13 billion years ago, so a distance of about 13 billion light-years is widely cited in the media (or sometimes a more precise figure of 13.035 billion light-years), although this would be "the distance of light travel" ( see Distance measurement (cosmology)) rather than "the exact distance" used in Hubble's law and in defining the observable size of the universe (cosmologist Ned Wright argues against the common use of light travel distance in astronomical press releases on this page, and at the bottom of the page offers an online calculator that can be used to calculate the exact current distance to distant objects in a flat universe based on either redshift z or travel time of light). The exact distance to redshift 8.2 will be about 9.2 Gpc, or about 30 billion light-years away. Another record holder for the most distant object is a galaxy that is observed through and located outside Abell 2218, also with a light travel distance about 13 billion light-years from Earth, with observations from the Hubble telescope showing a redshift between 6.6 and 7.1 , and observations from the Keck telescope showing a redshift toward the upper end of this range, about 7. The galaxy light that is now observable on Earth will begin to originate from its source about 750 million years after the Big Bang.
Horizons
Source of the article : Wikipedia
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