ProtoStar Ltd is a private company incorporated in Bermuda , with U.S. operations based in San Francisco, California San Francisco , California and Asian operations based in Singapore . ProtoStar intended ... fleet.html title ProtoStar Fleet publisher ProtoStar ref Two satellites were acquired and launched. ProtoStar s anchor customer, Dish TV India Limited, is the largest direct to home television ... title Space Systems Loral Built ProtoStar I Satellite Successfully Performs Post Launch Maneuvers date ref Bankruptcy and auction ProtoStar Ltd filed for Chapter 11 Bankruptcy Protection in the United ... direct satellite tv provider protostar files for bankruptcy following defaults on loan agreements title Direct Satellite TV Provider, ProtoStar, Files for Bankruptcy Following Defaults on Loan Agreements ... ref ProtoStar sought and was made by the bankruptcy court to auction its two satellites off to pay its outstanding liabilities. The auction for ProtoStar I was set by the bankruptcy court for October ... title Bankruptcy Court Sets Protostar Auction Dates publisher SpaceNews.com date August 31, 2009 accessdate ... 89950 title Intelsat Wins ProtoStar 1 Satellite Auction publisher Tvtechnology.com date May 11 ... satellite telecom 091030 intelsat outbids eutelsat for protostar 1.html title Intelsat Outbids Eutelsat for Protostar 1 publisher SpaceNews.com date October 30, 2009 author Peter B. de Selding accessdate December 23, 2009 ref ProtoStar I The ProtoStar I satellite was built by Space Systems Loral SS ... ProtoStar s requirements. ref cite web url http www.ssloral.com html pressreleases pr20070105.html title Space Systems Loral Awarded Contract To Deliver Satellite To ProtoStar Ltd. publisher SS ... . ref name arianelaunch cite web url http www.arianespace.com site news releases 07 01 08 protostar release index.html title Arianespace to launch ProtoStar I publisher Arianespace ref On January 8, 2007 Arianespace announced that ProtoStar had contracted with Arianespace for the launch of ProtoStar ... more details
Star formation Image 123107main image feature 371 ys 4.jpg thumb righ 280px A protostar inside a Bok globule Artist s image . Image ESO IRS2.jpg thumb righ 280px The central part of the stellar cluster RCW Catalogue RCW 38 , around the young, massive star IRS2, taken with the NACO adaptive optics instrument attached to European Southern Observatory ESO s Very Large Telescope . Astronomers were able to discover that IRS2 is in fact a twin system composed of two almost equally massive stars. The astronomers also found a handful of protostars. A protostar is a large mass that forms by contraction out of the gas of a giant molecular cloud in the interstellar medium . The protostellar phase is an early stage in the process of star formation. For a one solar mass star it lasts about 100,000 years. It starts with a core of increased density in a molecular cloud and ends with the formation of a T Tauri star , which then develops into a main sequence star . This is heralded by the T Tauri wind , a type of super solar wind that marks the change from the star accreting mass into radiating energy. Observations have revealed that giant molecular clouds are approximately in a state of virial theorem virial equilibrium &mdash on the whole, the gravitational binding energy of the cloud is balanced by the thermal pressure of the cloud s constituent molecule s and dust particles. Although thermal pressure is likely the dominant effect in counteracting gravitational collapse of protostellar cores, magnetic pressure, turbulence and rotation can also play a role Larson, 2003 . Any disturbance to the cloud may upset its state of equilibrium. Examples of disturbances are shock waves from supernova ... onto the central condensation, it is considered to be in protostar stage. When the surrounding ... NGC 7538 , home of the largest discovered protostar which is about 300 times the size of our Solar System ... Protogwiazda pt Protoestrela ro Protostea ru simple Protostar sk Protohviezda fi Protot hti ... more details
Unreferenced date November 2010 Infobox VG title Protostar War on the Frontier developer Tsunami Media publisher Tsunami Media distributor designer Joe Ybarra engine version released 1993 genre Role playing game modes Single player ratings platforms DOS media Floppy Disk requirements input Computer keyboard Keyboard , Joystick Protostar War on the Frontier is a 1993 science fiction space combat and role playing game that was produced by Tsunami Media . It is the unofficial sequel to Starflight and Starflight 2 Trade Routes of the Cloud Nebula . Pelit s reviewer considered the combat system unplayable and ruinous to the whole. Citation needed date November 2010 Premise A covert operative is called into a region of space where an antagonistic race of Aliens known as the Skeetch are gaining power. As the Skeetch are currently waging war against Earth, the Protostar Initiative is launched in an attempt to convince four races of Aliens to join an Alliance to resist the Skeetch s advancement in the galaxy. Gameplay The entire galaxy can be explored by the player at their own discretion, where they can scour planets for resources discover and name new planets and lifeforms meet, negotiate and barter with alien species build up their finances battle hostile alien races locate new crew members and upgrade their weapons and ship systems. Races Humans Work for a space organization called The Newfront which is losing a battle against the Skeetch. Skeetch The game s antagonists. They are never receptive, always hostile and never surrender. They are also building nearly invulnerable war ships, called Dreadnoughts, one of which represents the final boss. Deresta A race of Aliens that excel in science, but are cowardly during battle. They tend to surrender immediately to whoever is attacking them. They are one of the races that the player must convince into an alliance. Vantu A more spiritual ... if they ve surrendered during battle. DEFAULTSORT Protostar War On The Frontier Category 1993 ... more details
Infobox Spacecraft Name SES 7 Organisation SES WORLD SKIES Country Netherlands Mission Type Communications satellite Communication Orbit regime Geostationary orbit Geostationary Launch Site International Launch Services Carrier Rocket Proton M Briz M Launch May 16, 2009 Mission Duration 15 years Major Contractors Boeing 601 HP Longitude 108.2 East Transponders Ku band 22 , S band 10 Coverage Asia South Asia, North East Asia, South East Asia SES 7 known as ProtoStar II Indostar II is a Dutch commercial communication satellite operated by SES World Skies .Originally launched by Boeing for ProtoStar Ltd and later purchased through auction by SES for SES WORLD SKIES unit for 180 million. SES 7 operates geostationary orbit and intended to be located at a longitude of 108.2 East covering South Asia and Asia pacific region.SES7 is built for optimized HD DTH direct to home satellite television service and broadband Internet access across the Asia Pacific region. The spacecraft was originally built for PanAmSat now Intelsat to be used as Galaxy 8iR, but that contract was terminated on November 15, 2002 References cite web url http space.skyrocket.de doc sdat indostar 2 protostar 2.htm title Indostar 2 ProtoStar 2 SES 7 publisher Gunter s Space accessdate 2011 05 04 cite web url http www.boeing.com news releases 2008 q1 080114b nr.html title Boeing Contract ProtoStar II publisher Boeing accessdate 2011 05 04 cite web url http www.ses worldskies.com worldskies satellites fleet ses 7 index.php title SES 7 Home Page publisher SES WORLD SKIES accessdate 2011 05 04 SES World Skies Orbital launches in 2009 Category Communications satellites Category 2009 in spaceflight ... more details
The stellar birthline is a predicted line on the Hertzsprung Russell diagram that relates the B V colour colour and luminosity of protostar s at the end of the initial phase of accretion onto them. ref cite journal author Stahler, S.W. year 1983 journal ApJ volume 274 pages 822 title The birthline for low mass stars bibcode 1983ApJ...274..822S doi 10.1086 161495 ref Prior to this point, the protostar is deeply embedded in the cloud of cosmic dust dust and gas from which it formed, and so radiates only in the far infrared . Once Stellar evolution evolutionary effects rarefy and disperse this cloud, the star becomes visible as a pre main sequence star pre main sequence object. The set of locations on the Hertzsprung Russell diagram where these newly visible stars reside is called the birthline , and is found to the right of the main sequence . The location of the stellar birthline depends on the stellar structure, the Accretion astrophysics accretion rate onto the star and geometry of this accretion, i.e. whether or not it is occurring through an accretion disk . This means that the location of the birthline is not uniquely defined. See also Hayashi track T Tauri star References references External links http jila.colorado.edu pja stars02 lecture29.ps several low quality plots with the stellar birthline Category Stellar evolution Category Hertzsprung Russell classifications zh it Birthline stellare ... more details
W33A is a protostar located approximately 12,000 light years away from Earth, in the constellation Sagittarius constellation Sagittarius . As a star in the early stages of formation, so has attracted the interest of astronomers, who observed that while the protostar is accumulating material from surrounding clouds of gas and dust, it is simultaneously ejecting fast moving jets of particles from its north and south poles. ref http sciencenow.sciencemag.org cgi content full 2010 127 3 A Master Blueprint for Making Stars , Science NOW Daily News, 27 January 2010 ref References reflist External links http adsabs.harvard.edu abs 2000ApJ...536..347G An Inventory of Interstellar Ices toward the Embedded Protostar W33A , by Gibb, E. L. Whittet, D. C. B. Schutte, W. A. Boogert, A. C. A. Chiar, J. E. Ehrenfreund, P. Gerakines, P. A. Keane, J. V. Tielens, A. G. G. M. van Dishoeck, E. F. and Kerkhof, O., The Astrophysical Journal, Volume 536, Issue 1, pp. 347 356, DOI 10.1086 308940, Harvard University http www.iop.org EJ abstract 1538 4357 671 2 L169 VLTI MIDI 10 m Interferometry of the Forming Massive Star W33A , by W. J. de Wit1, M. G. Hoare1, R. D. Oudmaijer1 and J. C. Mottram1, 2007 ApJ 671 L169 L172, doi 10.1086 525253, School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK Category Protostars Category Sagittarius constellation star stub ... more details
Photo erosion is the dispersion of the outer layers of a prestellar core by ionizing radiation of a nearby star , thus preventing these layers from accreting onto the protostar at the centre of the core, and thereby reducing the mass of the developing object so instead of forming a star, it may form a free floating brown dwarf or planetary mass object . ref http arxiv.org pdf astro ph 0408522 The formation of free floating brown dwarves and planetary mass objects by photo erosion of prestellar cores , A. P. Whitworth, H. Zinnecker, Astronomy & Astrophysics, Volume 427, Number 1, November III 2004, Page s 299 306, DOI 10.1051 0004 6361 20041131 ref References reflist astronomy stub Category Stellar evolution Category Brown dwarfs Category Planets ca Fotoerosi ... more details
Pre stellar cores are the nurseries of new stars, and are an early phase in the formation of low mass stars, before gravitational collapse produces a central protostar . The spatial distribution of pre stellar cores shows the history of their formation, and their sensitivity to the physics controlling their creation. Most of our Galaxy s star formation takes place in clusters and groups within large molecular clouds. These clouds are often turbulent, showing supersonic line widths and complex magnetic fields which play crucial roles in cloud physics. The properties of pre stellar cores within molecular clouds aid understanding of the large scale physical processes dictating star formation. ref http iopscience.iop.org 0004 637X 684 2 1240 fulltext The Mass Distribution and Lifetime of Prestellar Cores in Perseus, Serpens, and Ophiuchus ref References reflist Category Observational astronomy Category Pre stellar cores astronomy stub ca Nucli preestel lar ... more details
Starflight 2 Trade Routes of the Cloud Nebula is the 1989 sequel to the successful Starflight science fiction computer game . It was computer game developer developed by Binary Systems , and video game publisher published by Electronic Arts , for MS DOS DOS . Starflight 2 introduced many new features, including an interstellar trade based game economy , a new combat model, and dozens of Extraterrestrial life alien species , scattered across an even larger game map. Starflight 2 was ported to the Amiga and Apple Macintosh platforms by MicroMagic, Inc. in 1991. One unofficial sequel to the series, Protostar War on the Frontier Protostar , was created in 1993. Reception The game was reviewed in 1991 in Dragon magazine Dragon 165 by Hartley, Patricia, and Kirk Lesser in The Role of Computers column. The reviewers gave the game 3 out of 5 stars. ref name Dragon165 cite journal title The Role of Computers author Lesser, Hartley, Patricia, and Kirk journal Dragon issue 165 date January 1991 pages 47 55 ref See also Star Control II References reflist External links moby game id starflight 2 trade routes of the cloud nebula MSDOS game stub ElectronicArts stub strategy videogame stub rpg videogame stub Category 1989 video games Category Amiga games Category Mac OS games Category DOS games Category Electronic Arts games Category Science fiction video games Category Space simulation narrative based game Category Space trading and combat simulators Category Video game sequels de Starflight Starflight 2 ... more details
Starbox begin name IRAS 18162 2048 Starbox observe epoch J2000.0 International Celestial Reference System ICRS constell Sagittarius constellation Sagittarius ra RA 18 19 12 ref name simbad dec DEC 20 47 35 ref name simbad Starbox astrometry dist pc 1700 Starbox detail mass 10 radius ? luminosity 17,000 temperature ? metal ? rotation ? age 0 Starbox catalog names HH 80 81 IRS Starbox end IRAS 18162 2048 is a far infrared source discovered by IRAS spacecraft in 1983. It is associated with a massive 10 solar masses protostar , which accretes gas from a disk that surrounds it. IRAS 18162 2048 emits two collimated radio Polar jet jet s along its axis of rotation. The jets are made of chains of radio sources aligned in a southwest northeast direction. The northern jet terminates in Herbig Haro object HH 81N, while the southern one terminates in Herbig Haro objects HH 80 and HH 81. The total luminosity of IRAS 18162 2048 is about 17,000 solar luminosities. The total extent of this system of jets and radio sources is about 5 pc. ref name Carrasco Gonz lez2010 In 2010 HH 80 81 jet of IRAS 18162 2048 were found to emit polarized radio waves, which indicated that they were produced by relativistic electron s moving along the magnetic field estimated at 20 nT. This observation was the first of kind demonstrating that a protostar can have a magnetized jet. ref name Carrasco Gonz lez2010 References reflist refs ref name simbad cite web title SIMBAD Astronomical Database work Results for IRAS 18162 2048 url http simbad.u strasbg.fr Simbad accessdate 2011 05 03 ref ref name Carrasco Gonz lez2010 cite doi 10.1126 science.1195589 ref Category Sagittarius constellation Category Emission nebulae Category Protostars Category IRAS objects star stub nebula stub ... more details
envelope takes longer to collapse accrete collapse onto the protostar time millions of years or so ... the cloud. Even though it takes several millions of years for the cloud to accrete onto the protostar ... starhood. For the most part, the cloud has a chance to accrete onto the protostar before the violent ... more details
A The candidate protostar VLA 1623 and prestellar clumps , The Astrophysical Journal, vol. 406, pp. 122 141 See also Portal Star Bok globule Herbig Haro object Pre main sequence star Protostar ... more details
agglomerated into the protostar . A protostar is the denser parts of a cloud core, typically with a mass ... weight gravity, and continues to attract matter. The protostar, at first, only has about 1 of its final ... stops the infall of new mass. The protostar is now considered a young star since its mass is fixed ... more details
Orphan date October 2008 The CHondritic Unfractionated Reservoir or CHUR is a scientific model in astrophysics and geochemistry for the mean chemical composition of the part of the Solar Nebula from which, during the formation of the Solar System, chondrite s formed. This hypothetic chemical reservoir is thought to have been similar in composition to the current photosphere of the Sun . When the Sun formed from its protostar , around 4.56 billion years ago, the solar wind blew all gas wiktionary Particle particle s from the central part of the Solar Nebula. In this way most lighter volatiles volatile elements e.g. hydrogen , helium , oxygen , carbon , that had not yet condensed in the inner, warmer regions of the nebula, were lost. This fractionation process is the reason why the terrestrial planet s and asteroid belt are relatively enriched in heavy elements in respect to the Sun or the gas planet s. A certain type of meteorites, carbonaceous chondrite C1 chondrites , have a chemical composition that is almost identical to the solar atmosphere the photosphere , except for the abundances of light volatile elements. They are considered to have the same composition as the solar nebula after the solar wind fractionated the lighter elements and therefore are representative for the material from which the terrestrial planets, including the Earth, were formed. See also chondrite nebular hypothesis Category Astrophysics Category Geochemistry nl Chondritic unfractionated reservoir ... more details
The Hayashi track is a path taken by protostar s in the Hertzsprung Russell diagram after the protostellar cloud has reached approximate hydrostatic equilibrium . In 1961 Ch shir Hayashi showed that there is a minimum effective temperature equivalently, a boundary on the right hand side of the H R diagram cooler than which hydrostatic equilibrium cannot be maintained this boundary corresponds to a temperature around 4000 kelvin K . Protostellar clouds cooler than this will contract and heat up until they reach the Hayashi boundary. Once at the boundary, a protostar will continue to contract on the Kelvin Helmholtz mechanism Kelvin Helmholtz timescale , but its effective temperature will no longer increase, as it will remain at the Hayashi boundary. Thus the Hayashi track is close to a vertical line on the H R diagram. Stars at the Hayashi boundary are fully convective this is because they are cool and highly Opacity optics opaque , so that radiative energy transport is not efficient, and consequently have large internal temperature gradients. Stars with masses 0.5 Sun Solar mass remain on the Hayashi track i.e. are fully convective throughout their pre main sequence star pre main sequence stage, joining the main sequence at the bottom of the Hayashi track. For stars with masses 0.5 Sun Solar mass the Hayashi track ends, and the Henyey track begins, when the internal temperature of the star rises high enough that its central opacity drops and radiative energy transport becomes more efficient than convective transport the lowest luminosity on the Hayashi track for a star of a given mass is thus the lowest luminosity at which it is still fully convective. The convection on the Hayashi track means that stars will reach the main sequence with a fairly homogeneous composition. See also Hayashi limit References Cite journal last Hayashi first C. title Stellar evolution in early phases of gravitational contraction journal Publ. Astron. Soc. Jap. volume 13 pages 450 452 ... more details
Unreferenced auto yes date December 2009 A pre main sequence star also known as a PMS star and PMS object is a star in the stage when it has not yet reached the main sequence . It can be a T Tauri star or FU Orionis star 2 Sun solar mass or an Herbig Ae Be stars 2 8 Sun solar mass . The energy source of these objects is gravitational contraction as opposed to Proton proton chain reaction hydrogen burning in main sequence stars . On the Hertzsprung Russell diagram , the pre main sequence stage of stars with masses 0.5 Sun Solar mass translates into a move along Hayashi track s almost vertically down and later along Henyey track s almost horizontally to the left, towards the main sequence . PMS stars can be differentiated from main sequence dwarf stars by using stellar spectra to measure the correlation between gravity and temperature. A PMS star will have a larger radius than a main sequence star, and thus be less dense and have lower surface gravity. While the surrounding matter is falling onto the central condensation, it is considered to be a protostar . When the surrounding gas dust envelope disperses and accretion process stops, the star is considered as pre main sequence star. Pre main sequence stars become optically visible after stellar birthline . Pre main sequence stage will last less than 1 of a star s life in contrast, the star will spend about 80 of its life on the main sequence . It is believed that during this stage all stars have dense circumstellar disk s, probable sites of planet formation. See also Portal Star Protoplanetary disk Protostar Young stellar object Star DEFAULTSORT Pre Main Sequence Star Category Star types Category Star formation Category Hertzsprung Russell classifications Astronomy stub ca Estrella pre seq ncia principal es Estrella presecuencia principal eu Sekuentzia nagusiaren aurreko izar fr toile de la pr s quence principale ko hi it Stella pre sequenza principale ja pt Estrela pr sequ nci ... more details
Tsunami Games or Tsunami Media, Inc. was an United States American video game developer and video game publisher publisher founded in 1991 by former employees of Sierra Entertainment then known as Sierra On Line . ref name moby cite web last first title Tsunami Media, Inc. publisher MobyGames date url http www.mobygames.com company tsunami media inc accessdate 2010 01 13 ref The company was based in Oakhurst, California , which at the time was also the home of Sierra. Between 1992 and 1996 Tsunami published several games, most notably adventure game s and interactive movie s, before becoming defunct. History Tsunami Games was formed in 1991 by Edmond Heinbockel, former chief financial officer of Sierra On Line. Its early games were point and click adventure game s including Ringworld Revenge of The Patriarch , which was based on the Ringworld novels by Larry Niven . Blue Force , a police procedural adventure game, was designed by Jim Walls , the former designer of the Police Quest series at Sierra. Also notable was Protostar War on the Frontier 1993 , a space exploration and adventure game in the style of Starflight . Interactive movies Tsunami made three interactive movies. Flash Traffic City of Angels 1994 and Silent Steel 1995 are full motion video based game s in which the player watches video clips and is asked to choose one of three options approximately every 15 seconds. These choices generally affect the game s story. Silent Steel was reportedly honored by PC Entertainment Magazine for Best Use of Live Action Footage in a CD ROM game. ref name moby The third interactive movie is Man Enough , a dating sim which includes ostensibly sexy live action video sequences. ref cite web last first title Man Enough publisher MobyGames date url http www.mobygames.com game man enough accessdate 2010 01 13 ref List of games Ringworld Revenge of The Patriarch 1992 Wacky Funsters 1992 Geekwad Games of The Galaxy 1992 Blue Force 1993 Protostar War on the Frontier 1993 Return ... more details
Diffuse nebula image caption NGC 7538 br SII Red, H alpha H Green, OIII Blue name NGC 7538 epoch J2000.0 type Emission nebula Emission or Reflection constellation Cepheus constellation Cepheus ra RA 23 13 45.7 ref name simbad cite web title SIMBAD Astronomical Database work Results for NGC 7538 url http simbad.u strasbg.fr Simbad accessdate 2006 10 20 ref dec DEC 61 28 21 ref name simbad dist ly 1 E19 m 9,100 light year ly 2,800 parsec pc ref name Balogetal2004 cite journal author Balog, Z. Kenyon, S. J. Lada, E. A. Barsony, M. Vink , J. G spar , A. title A Near Infrared JHK Survey of the Vicinity of the H II Region NGC 7538 Evidence for a Young Embedded Cluster journal The Astronomical Journal year 2004 volume 128 issue 6 pages Issue 6, pp. 2942 2953. bibcode 2004AJ....128.2942B doi 10.1086 425548 arxiv astro ph 0409115 ref appmag v size v 9 .00 6 .0 radius ly absmag v notes Contains largest known protostar names Bubble Nebula, John Louis Emil Dreyer Dreyer s Object, Sharpless catalog Sharpless 158 NGC 7538 , near the more famous Bubble Nebula , is located in the constellation Cepheus constellation Cepheus . It is located about 9,100 light years away from earth. It is home to the biggest yet discovered protostar which is about 300 times the size of our Solar System . It is located in the Perseus Spiral Arm of the Milky Way and is probably part of the Cassiopeia OB2 complex . ref name Balogetal2004 It is a region of active star formation including several luminous Infrared near IR and far IR sources. ref name Balogetal2004 References reflist Sh2 objects Category NGC objects 7538 Category Cepheus constellation Category H II regions Category Sharpless objects 158 az NGC 7538 eo NGC 7538 fa hr NGC 7538 it NGC 7538 ru NGC 7538 sk NGC 7538 sr NGC 7538 tr NGC 7538 uk NGC 7538 ... more details
A quasi star also called black hole star is a hypothetical type of extremely massive star that may have existed very early in the history of the Universe. Unlike modern stars, which are powered by nuclear fusion in their cores, a quasistar s energy would come from material falling into a central black hole. ref name newsci cite news url http space.newscientist.com article dn12982 biggest black holes may grow inside quasistars.html title Biggest black holes may grow inside quasistars date 29 November 2007 publisher NewScientist.com news service first Stephen last Battersby ref A quasi star is predicted to form when the core of a large protostar collapses into a black hole during its formation and the outer layers of the star are massive enough to absorb the resulting burst of energy without being blown away as they are with modern supernova e . Such a star would have to be at least one thousand times the mass of the Sun . ref name newsci Stars this large could only form early in the history of the Universe before the hydrogen and helium were contaminated by heavier elements see Population III stars. Once the black hole had formed at the core of the protostar, it would continue generating a large amount of radiant energy from the infall of additional stellar material. This energy would counteract the force of the black hole s gravity, creating an equilibrium similar to the one that supports modern fusion based stars. ref name bra08 cite journal last Begelman first Mitch coauthors Rossi, Elena Armitage, Philip title Quasi stars accreting black holes inside massive envelopes journal MNRAS year 2008 volume 387 issue 4 pages 1649 1659 doi 10.1111 j.1365 2966.2008.13344.x bibcode 2008MNRAS.387.1649B ref A quasi star is predicted to have had a maximum lifespan of about one million years, after which the core black hole would have grown to about ten thousand solar masses. These intermediate mass black hole s have been suggested as the origin of the modern era s supermassive ... more details
distinguish2 relativistic jet , a polar jet emitted at relativistic particle relativistic speed distinguish2 Jet stream polar jet stream in meteorology A polar jet is a phenomenon often seen in astronomy , where streams of matter are emitted along the rotation axis of rotation of a compact object. It is usually caused by the dynamic interactions within an accretion disc . When matter is emitted at speeds approaching the speed of light , these jets are called relativistic jet s. The largest polar jets are those seen in Active galactic nucleus active galaxies such as quasar s. Other systems which often contain polar jets include cataclysmic variable star s, X ray binary X ray binaries and T Tauri star s. Herbig Haro object s are caused by the interaction of polar jets with the interstellar medium . Bipolar outflow s or jets may also be associated with protostar s young, forming stars , ref http www.astronomy.com asy default.aspx?c a&id 6432 ref or with evolved Protoplanetary nebula post AGB stars often in the form of bipolar nebula e unsolved physics Why do the discs surrounding certain objects, such as the centers of active galaxy galaxies , emit radiation jets along their polar axes? While it is still mostly a mystery to physicists how polar jets are formed and powered, the two most often proposed origins of this power are the central object such as a black hole , and the accretion disc . Accretion disc s around many stellar objects are able to produce jets, although those around a black hole are the fastest and most active. This is because the speed of the jet is around the same speed as the escape velocity of the central object. This makes the speed of a jet from an accreting black hole near the speed of light, while protostar jets are much slower. While it is not known exactly how accretion disc s manage to produce jets, they are thought to generate tangled magnetic field s that cause the jets to Collimated light collimate . The Fluid dynamics hydrodynamics of a ... more details
Refimprove date December 2009 In astronomy or planetary science , the frost line , also known as the snow line or ice line , refers to a particular distance in the solar nebula from the central protostar protosun where it is cool enough for hydrogen compounds such as water , ammonia , and methane to condense into solid ice grains. Depending on density, that temperature is estimated to be about 150 kelvin K . The frost line of our solar system is around 2.7 AU, near the middle of the asteroid belt . The term is borrowed from the notion of frost line in soil science . The lower temperature in the nebula beyond the frost line makes many more solid grains available for accretion astrophysics accretion into planetesimals and eventually planets . The frost line therefore separates terrestrial planets from gas giant jovian planets in the Solar system . ref cite book title Discovering the Universe last Kaufmann first William J. year 1987 publisher W.H. Freeman and Company isbn 0 7167 1784 0 page 94 ref However, gas giant planets have been found inside the frost line around several other stars so called hot Jupiter s . They are thought to have formed outside the frost line, and later migrated inwards to their current positions. Notes and references Reflist See also Solar nebula Nebular hypothesis DEFAULTSORT Frost Line Astrophysics Category Planetary science Astronomy stub cs Sn n ra astrofyzika es L nea de congelamiento eo Frostiga linio astronomio it Frost line lt erk no riba ja pl Linia niegu pt Linha do gelo ru zh ... more details
Cluster name Snowflake Cluster image epoch J2000.0 class open cluster constellation Monoceros ra dec dist ly 2.4 lightyear kly dist pc appmag v size v mass kg mass msol radius ly v hb age notes names NGC 2264 The Snowflake Cluster is a cluster in Monoceros and is included in NGC 2264 . Name The star s appear to have formed in regularly spaced intervals along linear structures in a configuration that resembles the spokes of a wheel or the pattern of a snowflake . Hence, astronomers have nicknamed their new discovery the Snowflake Cluster. Information Scientists believe that these are very young protostar s, or newborn stars. At a mere 100,000 years old, these infant structures have yet to crawl away from their location of birth. Over time, the natural drifting motions of each star will break this order, and the snowflake design will be no more. The Spitzer Space Telescope Spitzer observations show that just as theory predicts, the density and temperature of the initial star forming cloud dictates the spacing between the protostars. External links http www.spitzer.caltech.edu Media happenings 20051222 index.shtml Spitzer Spots Stellar Snowflake on the Christmas Tree Cluster http www.physorg.com news9311.html Spitzer Unveils Infant Stars in the Christmas Tree Cluster http www.spitzer.caltech.edu Media mediaimages sig sig05 028.shtml Stellar Snowflake Cluster http tomsastroblog.com ?p 530 The Christmas Tree Cluster NGC2264 star cluster stub Category Monoceros constellation Category Open clusters tr Kar tanesi y ld z k mesi zh ... more details
Infobox Book See Wikipedia WikiProject Novels or Wikipedia WikiProject Books name Protostars title orig translator image Image Protostars.jpg 200px image caption Cover of Protostars author edited by David Gerrold and Stephen Goldin cover artist Gene Szafran country United States language English language English series genre Science fiction short stories publisher Ballantine Books release date 1971 english release date media type Print Paperback pages x, 271 pp. isbn 0 345 02393 5 preceded by followed by about a science fiction anthology the astronomical objects Protostar Protostars is an anthology of science fiction short stories edited by David Gerrold and Stephen Goldin . It was first published in paperback by Ballantine Books in October 1971, and has been reprinted a number of times since. The book collects sixteen novelettes and short stories by various science fiction authors, including a few by the editors, with an introduction by Gerrold. Contents A Sort of Introduction David Gerrold What Makes a Cage, Jamie Knows Scott Bradfield I ll Be Waiting for You When the Swimming Pool is Empty James Tiptree, Jr. In a Sky of Daemons Laurence Yep L. Yep The Last Ghost Stephen Goldin Afternoon with a Dead Bus David Gerrold Eyes of Onyx Edward Bryant The World Where Wishes Worked Stephen Goldin Cold, the Fire of the Phoenix Leo P. Kelley Oasis Pamela Sargent Holdholtzer s Box David R. Bunch The Five Dimensional Sugar Cube Roger Deeley And Watch the Smog Roll In... Barry Weissman Chances Are Alice Laurance The Naked and the Unashamed Robert E. Margroff My Country, Right or Wrong Andrew J. Offutt Side Effect Pg Wyal Category 1971 books Category Science fiction anthologies sf book stub ... more details
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