Record-Breaking Galaxy Cluster Discovered | Hacker News Reader

Record-Breaking Galaxy Cluster Discovered

nasa.gov

90 pointsokket26 comments

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?

It pushed the earliest formation of such clusters ~700 million years further towards the Big Bang and adds to the mystery how such clusters could exist so early in the universe. We currently have no good answer for this question. From the abstract of the paper:

  The large integrated stellar mass at such high redshift
  challenges our understanding of massive cluster formation.

http://arxiv.org/abs/1604.07404

Allow me to be the devil's advocate here:

Why should we think its about any of us? Why not for human kind? Its one small observation for a man but one huge observation for mankind. :)

The opening line tells it all for you:

"A new record for the most distant galaxy cluster has been set".

For reference: https://en.wikipedia.org/wiki/List_of_the_most_distant_astro...

At this scale of time and given the size, age and distance of galaxies, it doesn't really mean anything that will ever change our lives.

https://en.wikipedia.org/wiki/Galaxy_cluster

We can't go there. Nothing from there will visit us.

If the big bang is even an actual thing, it still happened everywhere, whenever.

There are lots of galaxies, and they are old and far away.

you are very wrong. understanding the universe means understanding our very home, us, where we come from, where we are going to, how will this all end (ie in big contraction/endless expansion).

if this topic ain't for you, no problem, but it's extremely interesting to many others.

A classic: http://www.lettersofnote.com/2012/08/why-explore-space.html

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

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

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

It's basically an experiment that has been running for billions of years. As you go forward in time (closer to earth) you also find more initial setup conditions - almost like scrubbing back and forth in a photographic timeline.

It's an amazing database of real-world physics that we can test our predictions against. These astronomical theories have a habit of trickling down. Consider the impact of having a massive fusion generator in our solar system: fusion energy is something that could have a rather substantial impact on every human being.

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?

A lot of research in astronomy is conducted to figure out how bright certain objects are, one classic example is "Cepheid variable" stars, these pulsate at a rate correlating with their brightness.

You're right in that there is sometimes debate about whether the "standard candles" as they're referred to are as bright as we expect, see: https://en.wikipedia.org/wiki/Cosmic_distance_ladder#Problem...

I always understood the distance is measured by the amount of red shift: the further away a galaxy is, the faster it moves away from us due to the expansion of the universe. As a result, the wavelength of the light originating from this galaxy is streched moving it more to the red end of the spectrum. The amount of red shift can be used to calculate the distance of an object fairly accurately.

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...). 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.

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.

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?

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

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.

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?

The Planck constant presumably, if we can get that far.

https://en.wikipedia.org/wiki/Planck_constant#Significance_o...

I don't understand the actual science well enough myself to explain, but my understanding is that there are lots of limits to do with optics, the behaviour of light over such distances, the wavelike nature of light, etc.

See https://en.wikipedia.org/wiki/Diffraction-limited_system for example.

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

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.

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

(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.)

> Telescope time is too valuable to "waste" but I wonder what it might show us.

It would be great if we could build more of them. I'm hoping that the cheaper access to space coupled with some clever hacks will let us throw a few more up there.

I would say that galaxy clusters forming after only 2.6B years is an indication that our models are already wrong.

Reply on news.ycombinator.com