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Astronomers Identify Very Distant (But Not the Most Distant) Galaxy

The views expressed are those of the author and are not necessarily those of Scientific American.


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distant galaxy 13 billion years ago

Credit: NAOJ

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 years for its light to reach us will be seen here as it appeared two billion years ago. Remarkably, today’s best telescopes can look across the majority of cosmic time, spying on galaxies as they looked just hundreds of millions of years after the big bang.

That’s just what a team of Japanese researchers has now done with the 8.2-meter Subaru Telescope in Hawaii. The group, led by Takatoshi Shibuya of the Graduate University for Advanced Studies in Tokyo and the National Astronomical Observatory of Japan, found what appears to be a galaxy 750 million years or so after the big bang. 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 exceedingly numerous, so they do not get names as snappy as those assigned to nearby galaxies such as Andromeda or Fornax. The newfound galaxy is known as SXDF-NB1006-2, after the area of sky in which it was found (the Subaru/XMM-Newton Deep Field, or SXDF) and the infrared filter at Subaru with which it was identified (NB1006).

Light from objects so distant has been stretched toward longer wavelengths as it travels across the expanding universe, and astronomers and cosmologists use the degree of stretching, or redshift, as a measure of distance traveled. In the case of SXDF-NB1006-2, the redshift implies that the object existed nearly 13 billion years ago.

Such objects are incredibly useful markers of the universe’s overall state during an early, transitional phase. Around the time that SXDF-NB1006-2 emitted the light now reaching telescopes on Earth, the neutral hydrogen atoms of intergalactic space were being ionized by newly formed stars and galaxies. Shibuya and his colleagues looked for objects in the sky emitting a specific wavelength of light from hydrogen atoms known as the Lyman alpha line. Lyman alpha photons can pass through ionized hydrogen but are blocked by neutral hydrogen. Measuring the number of galaxies visible as Lyman alpha emitters at various redshifts, then, can help pinpoint when the universe switched from neutral to ionized.

To calculate the redshift of SXDF-NB1006-2, the researchers took spectra of the object with the 10-meter Keck II telescope in Hawaii, breaking down the galaxy’s light into its component wavelengths. They identified a spectral line that seems to be Lyman alpha emission from a redshift of 7.215. A few other candidate galaxies at similar redshifts were discarded due to inconclusive spectra or variations in brightness that indicated that the object in 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 it was accompanied by a misleading press release proclaiming SXDF-NB1006-2 “the most distant galaxy ever found.” The researchers make no such claim in their study, and in recent years astronomers have located dozens and dozens of galaxies at redshifts of approximately 8 and one probable galaxy at a redshift of about 10, corresponding to a time 500 million years after the big bang. Those exceedingly faint objects have not generally been followed up with spectral observations, in the way that Shibuya and his team have done, limiting the precision of the cosmic distance estimates. But there is at least one galaxy more distant than SXDF-NB1006-2 that received spectral follow-up. In a 2010 study, astronomers found 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 Southern Observatory’s Very Large Telescope in Chile. That object, UDFy-38135539, existed just 600 million years after the big bang.

About the Author: John Matson is an associate editor at Scientific American focusing on space, physics and mathematics. Follow on Twitter @jmtsn.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. VIP 2:55 pm 06/7/2012

    “… as they looked just hundreds of millions of years after the big bang”.
    I am getting very tired of supposedly intelligent people referring to the ‘big bang’ as a beginning of everything. Has it never occurred to them that there is no beginning and there is no end, not in time or in space? There is ample proof for that reality, there is no proof for anything else.

    Link to this
  2. 2. geojellyroll 7:32 pm 06/7/2012

    VIP

    Yes, we do have a beginning to time and space as we know them…the Big Bang. It is the beginning of ‘everything’ we are ware of.

    Of course it occurs to cosmologists, physicists, etc. that there may be multiverses, etc. You need to google and you will find all types of papers, books, etc. on these theories. And no, there is not ‘ample proof’ that there is no end to time or space. We only have ‘proof’ of what we can measure in this Universe. One can ‘speculate’ on other existences but no evidence for them other than educated speculation.

    Bottom line. Big Bang theory accounts for time and space. It accounts for matter and energy in the states that we observe them.

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  3. 3. Dr. Strangelove 12:02 am 06/8/2012

    The amazing thing about very distant galaxies is not only you can look into the past, they are also moving faster than light. That is if they still exist at the present time, which we don’t know since we can only see their past. If their redshift > 3, their recessional velocity is > speed of light.

    It doesn’t violate special relativity since it is due to the expansion of spacetime itself, which is faster than light.

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  4. 4. newman 8:11 am 06/8/2012

    Increasingly, we will find new galaxies.
    The universe is huge.
    Over time we’ll have new discoveries because the universe is expanding rapidly and our technology is more advanced, would have more news in the cosmos!
    The big bang theory is just the beginning, she gave the first clues about our past and with these findings we can observe our future.

    Link to this
  5. 5. JacobSilver 9:54 am 06/8/2012

    If these galaxies are moving faster than the speed of light, presumably relative to us, then how could we see them? The light would constantly recede and never reach us.

    It is true that the galaxies, and stars, we see in the telescope are images from the past. But that is true of all images which reach our eyes.

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  6. 6. lahatton 5:58 pm 06/8/2012

    The article while not addressing the concept directly, is about time. More specifically, linear time – that being event after event after event in sequence. I, for one, am glad of linear time as it makes my life easy to comprehend as opposed to non-linear time – that which the events come in any sequence and can be relived at will. This also begs the question of liner non-linear time … But let’s not go there.

    There is a beginning, a middle and an end to our time with numerous examples to support this concept. There are species on earth that only live one day, others that live 70-100 years, etc. That is they are born, mature, procreate, and die. This can be said for planets and other heavenly bodies as well, although the time frames here are very large, usually measured in terms of billions of years. We have evidence to show that stars are born, mature, and die.

    The best Human kind can do is to observe and report on what it sees using the context that it has as objectively as possible. We can ponder the infinite as needed, discuss the ideas of alternative universes at will, and even consider the concept of a higher power that started all of this. The other side says that the universe has always been here and will continue that way forever. This in itself is interesting, but does not account for the birth/mature/death cycle that is all around us everywhere. Time is only measured by those that care, at this time human kind. The flora and fauna of the world have different concepts of time as they relate to the world at large.

    So let us rejoice in what we can observe and try to keep it in context at all times. Who knows, one of these days we may find that we are just a nightmare in the dreams of some cosmic creature that is incomprehensible to humankind.

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  7. 7. Chris2 5:54 am 06/9/2012

    Black hole: The Schwarzschild radius, i.e. the radius of the corresponding black hole, is simply defined for any arbitrary mass. If the density is such that the mass fits inside the S. radius, you have a black hole. The conventional picture is that the mass of the black hole is concentrated in a singularity at its centre. Please fault my argument against this picture, which might be an extreme special case: The finite mass of our universe defines a S. radius. Since the expanding universe was much smaller in previous times, it must have been a black hole (it might still be!), but its mass is nicely distributed and expanding – definitely no singularity. Total mass, not density is the criterion. And the definition of the S. radius obviously allows black holes within black holes – as we observe signs of numerous black holes within the universe.

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  8. 8. vinodsehgal1957@yahoo.com 10:11 am 06/9/2012

    During the period of Hubble in 1929-30, only one galaxy MW was known and beyond that light was classified as nabula. During the past of about 80 years, with the advancement of technology, million and billion of galaxies have been identified some as remote as 13 billion years past in time i.e. merely 500-700 million years after BB. A natural question which comes to mind : During this period of about 500-700 million years, had stars been born, matured enough and evolved into a gravitational stable galaxy system ? Even our solar system, which is a very very miniscule of the entire universe, could not mature into a stable system in this span.

    So far Astronomers have identified remotest galaxy having red shift of 10.5, corresponding to time scale of 13.2 billion years in past. This trend of searching galaxies at increasing distances corresponding to decreasing time scales after Big Bang is on continuous rise. If after some time, with the present technology or improved technology namely launch of James Webb telescope, a galaxy or some other heavenly body, having higher red shift corresponding to past period beyond 13.72 billion years i.e. age of the observable universe, is identified, this may leave a question mark on the entire BB cosmology. In that circumstance, astronomers may provide some novel explanation or extend the age of observable universe but never question the validity of BB cosmology since negation of expansion of space, which forms the very basis of BB cosmology, will require the revision of cosmological sciences of past 80 years

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  9. 9. ajinich 1:50 pm 06/9/2012

    Can someone answer this (apparent?) paradox?: if we observe a galaxy 750 million years after Big Bang, its position was much closer to us, so it should look enormous. Why isn’t it so?

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  10. 10. vinodsehgal1957@yahoo.com 2:02 am 06/10/2012

    To Ajinich

    I think astronomers describe that in remote past when universe was small, galaxies were closer. However, due to continuous expansion of space between them, galaxies dispersed away from each other. Therefore, in past at the the time of emission of light, though light emitting galaxy, which emitted light after about 750 million years from BB, and MW might be much closer running into a billion or few hundred million light years, but due to expansion of space, that light is being detected now in MW after 13 billion years. Since light traveled distance is 13 billion light years, therefore, light emitting galaxy will not appear enormous. There is also the possibility that at the time of emission, MW might not have existed but light propagated towards that part of sky in which MW came into existence subsequently

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  11. 11. Dr. Strangelove 11:16 pm 06/10/2012

    “If these galaxies are moving faster than the speed of light, presumably relative to us, then how could we see them? The light would constantly recede and never reach us.”

    When the light photons reach your eyes, you will see the galaxy. The galaxy is receding not the light photons.

    “if we observe a galaxy 750 million years after Big Bang, its position was much closer to us, so it should look enormous. Why isn’t it so?”

    The light photons spread out due to the expansion of spacetime so the galaxy appears to be far away and it is really far away at present time. When the light photons were emitted 750 million years ago, it was closer to our galaxy if it existed at that time.

    Link to this
  12. 12. Carlyle 9:05 am 06/11/2012

    11. Dr. Strangelove: ‘The light photons spread out due to the expansion of spacetime so the galaxy appears to be far away and it is really far away at present time. When the light photons were emitted 750 million years ago, it was closer to our galaxy if it existed at that time.’

    I am sure you meant to say, 750 million years after the big bang.

    Link to this
  13. 13. Postman1 11:42 am 06/11/2012

    I thought redshift indicated the speed at which an object was moving away from us at the time the light was emitted. This article states that “cosmologists use the degree of stretching, or redshift, as a measure of distance traveled.” Distance does not indicate speed, nor is the opposite true. This sounds like a fundamental change, but I am not a physicist, so I am certain to be missing something. Geo?

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  14. 14. vinodsehgal1957@yahoo.com 9:49 am 06/12/2012

    To Dr Strangelove(11) and Cariyle (12)

    In past, after 750 million years from BB, a galaxy had emitted some light which we are detecting now on earth. At that time neither MW nor earth were existing. MW came into existence some 12 billion years ago and earth was born some 4.5 billion years ago. Light emitted by galaxy entered some part of sky, where earth came into existence subsequently. At the time of emission either that galaxy was not receding faster than light Or light after some propagation entered that part of space which was receding slower than speed of light. That is the reason we are detecting its image now on earth. This detected signal, if not distorted substantially by gas/dust concentration or gravitational field on en-route journey, should indicate the than image of galaxy as existing 750 million years after BB.

    How we assume that that galaxy was enormous in size after 750 million years after BB?. Galaxies merge with other galaxies and grow in size with the passage of cosmological time scales. At present, that galaxy might have become enormous and located billion of years ( definitely more than 30 billion light years away) from MW. May be that galaxy might have become extinct. There is no way to find the present status of that galaxy

    But what we are detecting now is the image of galaxy as it existed 750 million years after BB

    Yes, since light has traversed a distance of 13 billion light years, therefore, galaxy appears farther. But it carries the same image of galaxy as it existed 750 million years after BB.

    Cosmology speaks of past reality which existed billion years ago. Irony is that there is no way to find the present day reality of universe. we are blind to present reality.

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