
Observable universe contains ten times more galaxies than previously thought - yurisagalov
http://astronomynow.com/2016/10/13/observable-universe-contains-ten-times-more-galaxies-than-previously-thought/
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jessriedel
Main HN discussion is here:

[https://news.ycombinator.com/item?id=12702759](https://news.ycombinator.com/item?id=12702759)

Incidentally, it is interesting to see how many folks uniformly have the same
misconception that dark matter is only about explaining galactic rotation
curves. Obviously it's not at all surprising or troubling that laymen aren't
experts, but the mistaken information is really far from random.

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valarauca1
To answer questions:

1) We still need dark matter. This mostly focuses on small satellite galaxies.
Not galactic rotation, galaxy cluster interaction, or light lending though
Galaxy Clusters.

2) The main interesting tidbit is that it seems the density of Galaxies in the
Universe has changed sharply in the past 1billion years. Which may lend more
data points to Dark Energy/Inflation models.

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ythl
We build a bigger, better telescope. Soon... "Observable universe contains
100x more galaxies than previously thought"

Downvote me all you want, I've seen the predicted amount of galaxies in the
universe increase by factors of 10 and 100 time and time again over the years.
This is not the first time our scientists' best guess has increased by a
factor of 10 and it won't be the last.

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elorant
Could that mean that we don't need a dark matter theory?

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strebler
I don't think so. Dark matter is needed to explain the contents / behavior of
galaxies we can see. This article is talking about galaxies we can't see.

On that note, here's some interesting / related recent news in terms of a
galaxy we have a hard time seeing:
[https://www.washingtonpost.com/news/speaking-of-
science/wp/2...](https://www.washingtonpost.com/news/speaking-of-
science/wp/2016/08/25/a-new-class-of-galaxy-has-been-discovered-one-made-
almost-entirely-of-dark-matter/)

~~~
dogma1138
It's very important to note that unlike what the media reports, there is no
new classification in astronomy of "dark matter galaxies" added due to this
discovery.

This is the original paper for Dragonfly 44
[https://arxiv.org/abs/1606.06291](https://arxiv.org/abs/1606.06291)

There are a lot of question about the composition of that galaxy, and what
makes it so dimm, but we need a lot more observations of that galaxy in order
to even start asking the right questions including full spectral analysis from
multiple observations and tools, correct redshifting and depth placement,
ensuring that there is nothing in the way that could explain why it is so dim
and many more other factors.

We also need to find other candidates of highly/ultra diffused galaxies in
order to even start to try to figure out what is going on.

~~~
strebler
Yes I read the paper and I know what you mean, the media loves to jump to
conclusions. Of course, they're also the reason I even found out about it. I'm
super excited to read what comes from the future observations.

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helthanatos
Plot twist: they don't actually exist; it's like looking into the sparkles in
car paint under a constantly changing POV and direction of light.

