Observable universe
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Posted on March 22, 2011 by Ashley Corbion . Cosmology sometimes seems mysterious: you often hear about dark matter, dark energy , big bang , multiverse , extra dimensions … I think we can undoubtedly say that our Universe is weird… And fascinating. A problem with some of these yet to be explained mysteries is that the models created to describe them are mainly purely theoretical, without being testable. This is particularly true with theories involving extra dimensions (who said string theory?..). Other theories even explore the possibility of lower dimensionality, in which the Universe had a smaller number of spatial dimensions in the past. Recently, physicists Jonas Mureika from Loyola Marymount University in Los Angeles, California, and Dejan Stojkovic from SUNY at Buffalo in Buffalo, New York, have proposed an interesting way to investigate lower dimensions of the Universe.
The vanishing dimensions of the Universe
Laser Space Telescope Could Test for Vanishing Dimensions
<img class="alignnone size-full wp-image-54618" title="LISA-waves" src="http://www.wired.com/images_blogs/wiredscience/2011/03/LISA-waves.jpg" alt="" width="660" height="495" /> The universe may have started out with fewer dimensions than the three we live in, and could still collapse down to one dimension at extremely high energies. The idea could solve some of the thorniest problems in particle physics and, unlike more popular models like string theory, can be tested with the next generation of space telescopes , according to a new study March 11 in Physical Review Letters . The problems arise from the standard model of particle physics, which successfully explains most of the universe but breaks down as it reaches the high energies that existed shortly after the Big Bang. The standard model still can’t explain why the expansion of the universe is accelerating, for example, or how to knit together the physics of extremely large and extremely small objects.
Apr. 20, 2011 — Did the early universe have just one spatial dimension? That's the mind-boggling concept at the heart of a theory that University at Buffalo physicist Dejan Stojkovic and colleagues proposed in 2010. They suggested that the early universe -- which exploded from a single point and was very, very small at first -- was one-dimensional (like a straight line) before expanding to include two dimensions (like a plane) and then three (like the world in which we live today). The theory, if valid, would address important problems in particle physics. Now, in a new paper in Physical Review Letters , Stojkovic and Loyola Marymount University physicist Jonas Mureika describe a test that could prove or disprove the "vanishing dimensions" hypothesis.
Primordial weirdness: Did the early universe have one dimension? Scientists outline test for theory
A member of the Local Group of galaxies, irregular galaxy Sextans A is 4.3 million light-years distant. The bright Milky Way foreground stars appear yellowish in this view. Beyond them lie the stars of Sextans A with young blue star clusters clearly visible. Distribution of the iron content (in logarithmic scale) in four dwarf neighbouring galaxies of the Milky Way.
Local Group
Milky Way
The Milky Way is the galaxy that contains our Solar System . [ 11 ] [ 12 ] [ 13 ] [ nb 1 ] This name derives from its appearance as a dim "milky" glowing band arching across the night sky, in which the naked eye cannot distinguish individual stars. The term "Milky Way" is a translation of the Classical Latin via lactea , from the Hellenistic Greek γαλαξίας κύκλος (pr. galaxías kýklos , "milky circle"). [ 14 ] [ 15 ] [ 16 ] The Milky Way appears like a band because it is a disk-shaped structure being viewed from inside. The fact that this faint band of light is made up of stars was proven in 1610 when Galileo Galilei used his telescope to resolve it into individual stars. In the 1920s, observations by astronomer Edwin Hubble showed that the Milky Way is just one of many galaxies. The Milky Way is a barred spiral galaxy 100,000–120,000 light-years in diameter containing 200–400 billion stars .
The Canis Major Dwarf Galaxy is a supposed (see Dispute section below) small irregular galaxy in the Local Group , located in the same part of the sky as the constellation Canis Major . The galaxy contains a relatively high percentage of red giant stars , and is thought to contain an estimated one billion stars in all. The Canis Major Dwarf Galaxy is classified as an irregular galaxy and is now thought to be the closest neighbouring galaxy to our location in the Milky Way , being located about 25,000 light-years away from our Solar System [ 2 ] and 42,000 light-years from the Galactic Center . It has a roughly elliptical shape and is thought to contain as many stars as the Sagittarius Dwarf Elliptical Galaxy , the previous contender for closest galaxy to our location in the Milky Way. [ edit ] Discovery
Canis Major Dwarf Galaxy
Andromeda Galaxy
The Andromeda Galaxy ( / æ n ˈ d r ɒ m ɨ d ə / ) is a spiral galaxy approximately 2.5 million light-years (2.4 × 10 19 km) from Earth [ 4 ] in the Andromeda constellation . Also known as Messier 31, M31 , or NGC 224 , it is often referred to as the Great Andromeda Nebula in older texts. The Andromeda Galaxy is the nearest spiral galaxy to our Milky Way galaxy, but not the closest galaxy overall. It gets its name from the area of the sky in which it appears, the constellation of Andromeda , which was named after the mythological princess Andromeda .
A star is a massive, luminous sphere of plasma held together by gravity . At the end of its lifetime, a star can also contain a proportion of degenerate matter . The nearest star to Earth is the Sun , which is the source of most of the energy on Earth. Other stars are visible from Earth during the night, when they are not obscured by atmospheric phenomena, appearing as a multitude of fixed luminous points because of their immense distance. Historically, the most prominent stars on the celestial sphere were grouped together into constellations and asterisms , and the brightest stars gained proper names. Extensive catalogues of stars have been assembled by astronomers, which provide standardized star designations .
Portal: Star
Educational video on supernovae explosions from NASA SN 2007ck and SN 2007co in the same galaxy A supernova (abbreviated SN , plural SN e after "supernovae") is a stellar explosion that is more energetic than a nova . It is pronounced / ˌ s uː p ər ˈ n oʊ v ə / with the plural supernovae / ˌ s uː p ər ˈ n oʊ v iː / or supernovas . Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy , before fading from view over several weeks or months. During this short interval a supernova can radiate as much energy as the Sun is expected to emit over its entire life span. [ 1 ] The explosion expels much or all of a star's material [ 2 ] at a velocity of up to 30,000 km/s (10% of the speed of light ), driving a shock wave [ 3 ] into the surrounding interstellar medium .
Supernova
Eta Carinae , in the constellation of Carina, one of the nearer candidates for a future hypernova A hypernova (pl. hypernovae ) is a type of supernova explosion with an energy substantially higher than standard supernovae . Such explosions are believed to be the origin of long-duration gamma-ray bursts . [ 1 ] Just like more normal supernovae, hypernovae are produced by several different types of stellar explosion, some well modelled and observed in recent years, some still tentatively suggested for observed hypernovae, and some entirely theoretical. Numerous hypernovae have been observed corresponding to supernovae type Ic and type IIn, and possibly also at least one of type IIb. [ 2 ]
Hypernova
Magnetar
Artist's conception of a magnetar, with magnetic field lines A magnetar is a type of neutron star with an extremely powerful magnetic field , the decay of which powers the emission of high-energy electromagnetic radiation , particularly X-rays and gamma rays . [ 1 ] The theory regarding these objects was proposed by Robert Duncan and Christopher Thompson in 1992, but the first recorded burst of gamma rays thought to have been from a magnetar was detected on March 5, 1979. [ 2 ] During the following decade, the magnetar hypothesis has become widely accepted as a likely explanation for soft gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs). [ edit ] Description Like other neutron stars , magnetars are around 20 kilometres (12 mi) in diameter and have a greater mass than the Sun .Observable universe
Visualization of the 93 billion light year – or 28 billion parsec – three-dimensional observable universe. The scale is such that the fine grains represent collections of large numbers of superclusters . The Virgo Supercluster – home of Milky Way – is marked at the center, but is too small to be seen in the image. In Big Bang cosmology , the observable universe consists of the galaxies and other matter that can, in principle, be observed from Earth in the present day—because light (or other signals) from those objects has had time to reach the Earth since the beginning of the cosmological expansion. Assuming the universe is isotropic , the distance to the edge of the observable universe is roughly the same in every direction.The Universe is commonly defined as the totality of existence, [ 1 ] [ 2 ] [ 3 ] [ 4 ] including planets , stars , galaxies , the contents of intergalactic space , and all matter and energy . [ 5 ] [ 6 ] The broadest definition of universe is that it is simply everything, while a narrower definition is that the universe is limited to what can be observed. [ dubious ] Similar terms include the cosmos , the world and nature . Scientific observation of the Universe, the observable part of which is about 93 billion light years in diameter, [ 7 ] has led to inferences of its earlier stages. These observations suggest that the Universe has been governed by the same physical laws and constants throughout most of its extent and history. The Big Bang theory is the prevailing cosmological model that describes the early development of the Universe, which in physical cosmology is calculated to have occurred 13.798 ± 0.037 billion years ago. [ 8 ]