

The Puzzling Galaxy at the Edge of Time and Space - DiabloD3
http://motherboard.vice.com/read/the-puzzling-galaxy-at-the-edge-of-time-and-space-3252351

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madaxe_again
Perhaps the most straightforward, albeit seismic, explanation for this and the
recent supermassive black hole is that we've misunderstood either the age of
the universe, or the nature of time.

The black hole is one thing, but a old yet seemingly ancient metal rich galaxy
is another - you only get heavy metals from fusion and time.

~~~
antognini
That explanation is extremely unlikely. Our constraints on the age of the
universe are now extremely tight and come from several independent
measurements.

What these results are more likely telling us is what the very first
generation of stars were like. There's currently a great deal of uncertainty
about how they form and what they're like. One of the reasons we know so
little about them is because no one has actually seen a first generation star.
Such a star would be characterized by having no metals at all. Some stars with
extremely low amounts of metals have been discovered (something like one
millionth the amount of metals in the Sun), but all have a detectable amount
of metals in their atmosphere. This means that: (1) there were very few first
generation stars, so they are extremely rare; and/or (2) the first generation
stars that formed were extremely massive, so they all had very short
lifetimes.

In addition to these observational uncertainties, there are major theoretical
uncertainties about the formation of first generation stars as well. Star
formation in general is poorly understood, but it is known that metals are
extremely important when forming stars. The reason for this somewhat
technical, but makes for an interesting diversion. If you have a gas cloud out
in interstellar space, it has some temperature. As the cloud collapses under
its own gravity, it heats up. However, according to the virial theorem twice
as much gravitational energy is lost as goes into heat -- this means that the
other half must be radiated away. But radiative transport in these clouds can
be inefficient. If your contracting gas cloud produces a photon, it will
pretty soon hit a hydrogen atom, bump it up to the next energy level, and then
be re-emitted when the hydrogen atom transitions back down to the ground
state. This will happen many, many times and the photon will bounce around the
cloud for a long, long time before it can random walk out of the cloud,
escape, and cool the cloud down. Remember, until the photon leaves the cloud,
the cloud cannot contract. However, if this photon hits a metal, electron will
jump up to some high energy level, and then cascade down to the ground state
through some complicated path and will emit several low energy photons. These
photons will be unable to bump any hydrogen atoms up to the next energy level
so they can travel through the cloud unimpeded. Thus metals are extremely
important for cooling clouds efficiently. The more metals a cloud has, the
more easily it can contract and form stars.

A direct consequence of this is that clouds with metals can fragment more
easily. This means that a large gas cloud will fragment into many smaller
subclouds and form lots of stars in a cluster. In the early universe, however,
it's not clear what happened. It may be that without metals clouds just didn't
fragment and so the first generation of stars were all truly massive -- maybe
hundreds to thousands of solar masses. But this scenario is problematic for a
number of reasons -- foremost among them, the gas needs to cool somehow, and
the cooling time seems to be too long to form these kinds of stars. There
might (probably even must) be some other way to cool these clouds to get them
to contract, but what other cooling mechanisms work on clouds without metals
is not well understood.

Results like this put constraints on how quickly the first generation of stars
must have formed, how massive they must have been (at least some of them), and
how many of them there must have been.

~~~
cristianpascu
Independent measurements but not necessarily independent assumptions, and
hence interpretations of those results.

~~~
antognini
The assumptions are pretty independent, too. The tightest constraints on the
age of the universe come from measurements of the Hubble constant from Type Ia
supernovae. There are certain assumptions in this measurement about how Type
Ia supernovae evolve over the age of the universe. The other constraints come
from the ages of the oldest globular clusters. The assumptions in this
measurement basically have to do with certain details of stellar physics.
There isn't much overlap between the two sets of assumptions.

------
sithu
I'm by no means a physicist but find topics on the nature of universe deeply
fascinating. One thing i've always found frustratingly difficult to grasp
though, is the expansion of the universe - but just found this article to be a
total eye opener:
[http://en.wikipedia.org/wiki/Metric_expansion_of_space](http://en.wikipedia.org/wiki/Metric_expansion_of_space)

It was counterintuitive to me how we can observe light from objects 12 billion
years old, when supposedly things are flying apart faster than the speed of
light. Is there an edge of the universe, and what is outside that we are
'expanding into'. If everything is moving apart, why are we going to crash
into Andromeda? Why haven't black holes consumed all the mass in the universe
by now? If the cosmological principle is true and the universe looks the same
in all directions, doesn't that imply that we're either at the center- or that
it wraps around and we just can't observe it? Saying it's infinitely large
seems like a convenient explanation.

The idea of metric expansion of space between gravitationally unbound matter,
local groups, and Hubble flow explain a lot.

I do still wonder though how accurate our understanding of the universe really
is, or if there's some fundamental thing we've missed and have generated
theories to fit the observations we're currently capable of making.

------
JoeAltmaier
Maybe we're seeing all the way around, and back to here again!

~~~
jckt
If you're referring to what Einstein referred to as the "finite, unbounded"
universe, i.e. a spherical topology of the universe, measurements from the
last decade and a half have shown that to be most probably (if not completely)
wrong[1], and that our universe is in fact "flat".

[1]
[http://map.gsfc.nasa.gov/universe/uni_shape.html](http://map.gsfc.nasa.gov/universe/uni_shape.html)

~~~
JoeAltmaier
Where's the romance in that?

------
ars
The trouble comes because they measured the age using metric-expansion
redshift.

But if there is something else affecting the redshift - for example a huge
galaxy in between with a strong gravitational pull then the galaxy will appear
more redshifted than it would otherwise, and is not actually as old as it
appears.

------
jgh
I'm a little confused - the article says it's 2.2 billion light years away yet
the expectation is that it would be a very immature galaxy. Wouldn't it have
had ~11.6 billion years to become a more mature galaxy before the light we're
looking at left?

The Earth is older than the light from that galaxy. So why the surprise at its
apparent maturity?

Edit: to answer my own question the galaxy cluster that's doing the magnifying
is 2.2 billion light years away. It took some googling to figure that one out!

~~~
civilian
> This galaxy is so distant that it would have been invisible without the
> gravitational lensing effects of a large galaxy cluster called Abell 1689,
> located nearly 2.2 billion light years away in the constellation Virgo.

Straight from the article. :)

~~~
jgh
Yes, I see now that I was only half paying attention to the article and
skipped a bunch of words ;)

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trey-jones
Is it not a possibility that this galaxy was already much further from the
"center" of the universe 12 billion years ago? I am not an astronomer by any
stretch.

~~~
rollo
There is no such thing as a center.

~~~
littletimmy
This point always confused me. Isn't the "center" just the point where the big
bang took place and started the expansion of the universe?

~~~
everyone
If you inflate a balloon, the surface area of the balloon increases and some
dots drawn on the surface would get further apart but you couldnt say that the
enlargement has a 'centre' The entire surface is simply expanding everywhere
at once. The universe is like that with an extra dimension.

~~~
bbcbasic
Still confused! With a balloon surface if you travel in one direction long
enough you will end up back where you started. Does this analogy apply to the
universe.

If there is no centre then either the universe is infinite, or it wraps around
on itself like a balloon?

~~~
everyone
I believe whether the universe wraps around, or is infinite is still a matter
of some debate. I know some researchers are currently trying to determine the
size and shape of the universe by trying to see all the way to the other side
and back to our side, for example. In some cases with things in physics and
cosmology, lets say dealing with 4 or 11 spatial dimensions you've just got to
accept that our minds are not designed to be able to visualize some concepts,
though we can understand and make progress by understanding the math. Heres a
random article introducing some ideas about the geometry and topology of the
universe. [http://io9.com/5811706/if-you-keep-going-around-the-
universe...](http://io9.com/5811706/if-you-keep-going-around-the-universe-
will-you-end-up-where-you-started)

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ccvannorman
I feel this is the appropriate place to bring up that we're not all confident
that the Big Bang actually happened at all.

[http://metaresearch.org/cosmology/BB-
top-30.asp](http://metaresearch.org/cosmology/BB-top-30.asp)

~~~
nitrogen
Even if the universe did not expand from a singularity, universal redshift is
still a thing, as is the CMB.

