Tag: Epoch of Reionization

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astronomy Cosmology Creation/evolution Physics

A long time ago, in a galaxy far far away…so the story goes

This time the story is about a galaxy of a billion stars that is allegedly seen from a time only 402 million years after the big bang. The galaxy is called GN-z11 because it supposedly has a redshift of 11.1,1 measured with the Hubble Space Telescope (HST). That is the highest redshift assigned to any galaxy to date, and according to big bang cosmology it corresponds to a distance of about 13.4 billion light-years. It allegedly extends the time of observation of the universe back a further 150 million years than previously known. It also places the epoch of this galaxy in the period of predicted formation of a huge number of stars and galaxy formation built from these first stars formed after the alleged big bang.2

GNz11
Figure 1: That blurry image is of a galaxy so far away it dates closer to the Big Bang, from a time when the universe was a mere toddler of about 400 million years old (so reads the caption from Ref. 6) . Credit: Space Telescope Science Institute via AP.

In a new analysis of the publicly available CANDELS data3 over the GOODS fields,4 a team of astronomers, with lead author Oesch,1 identified six relatively bright galaxies with best-fit photometric redshifts z = 9.2—10.2.  But photometric redshift determinations are very model dependent and not so conclusive, so they chose the intrinsically brightest of them for 12 orbit passes of the HST, to collect grism5 spectroscopic data and more accurately measure its redshift. This galaxy (now called GN-z11) was previously labelled GN-z10-1. It was previously given a photometric redshift zphot = 10.2. It has strong emission in the infrared consistent with a very bright ultra-violet galaxy after taking in to account stretching of the source optical wavelengths down to the infrared. See Fig. 1.

The authors in their paper write:1

GN-z11 is remarkably and unexpectedly luminous for a galaxy at such an early time:

It is about three times brighter than expected for the time of its alleged existence only 400 million years after the big bang. Early in the alleged big bang history, the first stars were supposed to have formed into small nondescript galaxies. They are meant to have many ‘young’ stars but since the galaxies are not meant to be very large it also follows that they should not be very bright. They’re expected to have grown large later by mergers with other galaxies, where galaxy size is correlated with its intrinsic brightness. In this case the GN-z11 galaxy has the intrinsic brightness of a galaxy observed at a redshift near z = 7, at a time when the big bang universe is three times larger. Thus it follows that the only galaxy they have identified at the epoch of 400 million years after the big bang is three times brighter than galaxies when the universe is allegedly much older and when galaxies should be much larger and hence brighter. This means “galaxy evolution” has worked too fast on this newly discovered galaxy. It is the opposite of what is expected.

Is the measurement solid?

Continue reading “A long time ago, in a galaxy far far away…so the story goes”
Categories
astronomy Cosmology Creation/evolution

Is there definitive evidence for an expanding universe?

Evolution out of the ‘Dark Ages’

Expansion of the universe is fundamental to the big bang cosmology. No expansion means no big bang. By projecting cosmological expansion backwards in time, they assert, one will, hypothetically, come to a time where all points are the same. Since these points are all there is, then it logically follows that there is no space or time ‘before’ this moment. It is the singularity, and we cannot use language couched in concepts of time when no time (or space) exists.

Yet there are Christians who use this presumed fact as evidence in support of the Genesis 1 account and even for the existence of God Himself. They argue that only God could have started the big bang. Though it is true the universe does need a first cause it is an enormous leap into the unknown to suppose that the big bang story is that which is described in the Genesis 1 narrative. The sequence of events is nothing like it. See The big bang is not a Reason to Believe!

Redshift
Redshifted The spectral lines for this element still show the same distinctive pattern, but all have been shifted towards the red end of the spectrum.

At the end of the 1920s, Edwin Hubble made a significant discovery. He found a proportionality between the amount by which the spectral lines in the light coming from relatively nearby galaxies are redshifted1 (z) and their distances (r) from Earth. That relationship is now called the Hubble law c z = H0 r, where c is the speed of light and H0 is Hubble’s famous constant of proportionality.

The Hubble law has since been extended to very great redshifts (therefore by inference, distances) in the cosmos, via the redshift-distance relationship. At small redshifts, and by interpretation at small distances, this becomes precisely the Hubble law.

Redshifts have been interpreted as a velocity of recession, i.e. that galaxies are moving through space. And that the recession implies expansion of the universe. But Hubble, up to the time of his death, was not so convinced of this interpretation.  He was open to the possibility that there could be another mechanism to explain redshifts.

Continue reading “Is there definitive evidence for an expanding universe?”