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Astronomers identify very distant (but not the most distant) galaxy by ferujkll sdff
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Astronomers identify very distant (but not the most distant) galaxy |
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The universe is a big place, and by peering across it astronomers get to look back in time . A galaxy or supernova so far away that it takes two billion yearsfor its light to reach us will be seen here as it appeared twobillion years ago. Remarkably, today s best telescopes can lookacross the majority of cosmic time, spying on galaxies as theylooked just hundreds of millions of years after the big bang. That s just what a team of Japanese researchers has now done withthe 8.2-meter Subaru Telescope in Hawaii. The group, led byTakatoshi Shibuya of the Graduate University for Advanced Studiesin Tokyo and the National Astronomical Observatory of Japan, foundwhat appears to be a galaxy 750 million years or so after the bigbang.
The study is now available online and has been accepted for publication in the Astrophysical Journal . Distant galaxies are hard to find, but they re exceedinglynumerous, so they do not get names as snappy as those assigned tonearby galaxies such as Andromeda or Fornax. The newfound galaxy is known as SXDF-NB1006-2, afterthe area of sky in which it was found (the Subaru/XMM-Newton DeepField, or SXDF) and the infrared filter at Subaru with which it wasidentified (NB1006). Light from objects so distant has been stretched toward longerwavelengths as it travels across the expanding universe, andastronomers and cosmologists use the degree of stretching, orredshift, as a measure of distance traveled.
In the case ofSXDF-NB1006-2, the redshift implies that the object existed nearly13 billion years ago. Such objects are incredibly useful markers of the universe soverall state during an early, transitional phase. Around the timethat SXDF-NB1006-2 emitted the light now reaching telescopes onEarth, the neutral hydrogen atoms of intergalactic space were beingionized by newly formed stars and galaxies. Shibuya and hiscolleagues looked for objects in the sky emitting a specificwavelength of light from hydrogen atoms known as the Lyman alphaline. Lyman alpha photons can pass through ionized hydrogen but areblocked by neutral hydrogen.
Measuring the number of galaxiesvisible as Lyman alpha emitters at various redshifts, then, canhelp pinpoint when the universe switched from neutral to ionized. To calculate the redshift of SXDF-NB1006-2, the researchers tookspectra of the object with the 10-meter Keck II telescope inHawaii, breaking down the galaxy s light into its componentwavelengths. They identified a spectral line that seems to be Lymanalpha emission from a redshift of 7.215. A few other candidategalaxies at similar redshifts were discarded due to inconclusivespectra or variations in brightness that indicated that the objectin question was a flaring black hole rather than an ordinary,distant galaxy. It s a very impressive piece of work, but it s too bad that itwas accompanied by a misleading press release proclaimingSXDF-NB1006-2 the most distant galaxy ever found.
The researchers make no such claim in their study, and inrecent years astronomers have located dozens and dozens of galaxies at redshifts of approximately 8 and one probable galaxy at a redshiftof about 10 , corresponding to a time 500 million years after the big bang.Those exceedingly faint objects have not generally been followed upwith spectral observations, in the way that Shibuya and his teamhave done, limiting the precision of the cosmic distance estimates.But there is at least one galaxy more distant than SXDF-NB1006-2that received spectral follow-up. In a 2010 study, astronomersfound a spectral line, albeit a faint one, that placed a galaxy at a redshift of 8.55 , using the Hubble Space Telescope and the European SouthernObservatory's Very Large Telescope in Chile. That object,UDFy-38135539, existed just 600 million years after the big bang. I am a professional writer from Special Purpose Bags & Cases, which contains a great deal of information about foldable mini keyboard , ntp time servers, welcome to visit!
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