
Record-Breaking Galaxy Cluster Discovered - okket
http://www.nasa.gov/mission_pages/chandra/record-breaking-galaxy-cluster-discovered.html
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bwang29
NASA is making a lot of "record-breaking" news in the past few weeks and it is
increasingly difficult for me to think how these news affect me and my
relationship to the Galaxy. I understood many of these discoveries translated
to "current science could be wrong". But if counting stars isn't my hobby,
what am I supposed to take a way from this and digest the meaning of 11.1B
light years distance?

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flamedoge
That's just how science is. It doesn't need to be driven by a business or
human "need".

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nononosisisi
The drive to satisfy our curiosity is a human need and what drives scientists.

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flamedoge
To me that is more of a desire than a need, but I digress.

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honkhonkpants
I always wondered about these measurements. Excuse me if this is rookie
astronomical information. I have read that we gauge the distance through
brightness. That is we know how bright such an object should be at the source,
and estimate the distance based on actual brightness at the instrument. How do
we know it's not just brighter than we believe, instead of being as far away
as we believe?

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adrianratnapala
Let's distinguish redshift from (the more murky notion of) distance.

Astronomers usually just think in terms of redshift and might never convert
into "X light years from Earth" until they write a press release. Red-shift is
measured directly, because we have all kinds of ways of knowing about the
spectrum expecte from various things, and we just see the expected pattern
shifted.

The calibrarion from red-shift to distance is done by considering the
brightness of objects. But here astronomers can just pick and choose those
objects for which they have good models.

An example is the type 1a supernova
([https://en.wikipedia.org/wiki/Cosmic_distance_ladder#Superno...](https://en.wikipedia.org/wiki/Cosmic_distance_ladder#Supernovae)).
These are stars that were actually _growing_ until the tripped over a very
specific mass threshold and went nova. Because they all had the same initial
mass, they all have the same brightness.

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dwarman
Not "wrong" \- just fractally revealed details. What I find amazing here is
thatit shows the fractal nature does not only work by looking into ever
smaller regions - we also are discovering fractally larger structures
exploring in the other scale direction.

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ImTalking
As our instruments get better, are we going to find these clusters further and
further out until we hit the supposed age of the universe @ 13.7B years? Then
what? When do we start thinking that maybe the models are potentially wrong?

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CapitalistCartr
When we have evidence to the contrary. Speculation about what we might find in
the future doesn't change anything.

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ChuckMcM
Exactly right. Its exciting because we get new data and if it contradicts
theory, it forces us to reconsider what we think is the correct answer. And in
that reconsideration our understanding grows.

It is unfortunate that we cannot image this object once a day for 5 years and
then watch its changes over that time period in one 30 minute viewing.
Telescope time is too valuable to "waste" but I wonder what it might show us.

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maxxxxx
Let's say our telescopes get better and better. Are there any hard limits for
how well we can resolve the light from such a galaxy?

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prewett
Practically, yes, telescopes are limited by the diffraction limit. This
depends on ratio of the wavelength of the light being captured to the size of
the optics. In theory one could make larger and larger perfect lenses/mirrors,
but practically there is a limit somewhere. More information at
[https://en.wikipedia.org/wiki/Angular_resolution](https://en.wikipedia.org/wiki/Angular_resolution)

I suppose at some point quantum effects will take over, but I'm guessing the
manufacturing requirements for perfect optics will be the limited factor long
before then.

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josePhoenix
For large-aperture ground-based telescopes operating in the visible spectrum,
the seeing limit is the dominant effect. Atmospheric turbulence is a bigger
factor than the precision of your optics, in other words. See
[https://en.m.wikipedia.org/wiki/Astronomical_seeing](https://en.m.wikipedia.org/wiki/Astronomical_seeing)

(Space telescopes are diffraction-limited but have other constraints, like
mass budget and cost, that keep them from being as large as ground based
facilities.)

