Thread: First stars
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Old May 19th 18, 10:09 AM posted to sci.astro.research
Phillip Helbig (undress to reply)[_2_]
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Default First stars

In article , jacobnavia
writes:

Le 18/05/2018 20:50, Bringfried Stecklum a écrit :
On 16.05.2018 13:22, Steve Willner wrote:
A recent _Nature_ article
http://adsabs.harvard.edu/abs/2018Natur.555...67B
shows evidence that the first stars appeared by z=20, about 180 Myr
after the Big Bang.


It looks the confirmation arrived quicker than thought. See ESO PR "The
onset of star formation 250 million years after the Big Bang"

https://www.eso.org/public/news/eso1815/

which also provides a link to the paper.


That's z=17. Looks nice z=17, with now an incredible bright QSO (quasar)
with 20 Billion (!) solar masses and so bright that its light arrives
directly to us, no gravitational lensing required, imagine. It is the
most brilliant object detected so far by humans.

https://arxiv.org/pdf/1805.04317.pdf

The star mentioned above has oxygen, what implies at least several
generations of stars to produce it,


Why? One generation will produce oxygen.

and then exploding and dispersing
the oxygen into space so that it slowly condenses into anew stars...


Stars big enough to form appreciable oxygen quickly will explode anyway,
so this is not an additional hurdle.

All that at z=17!


Keep in mind that the redshift, especially at high redshift, is a highly
non-linear function of age. There is much less difference between z=17
and z=12 than between z=0 and z=5.

20 Billion / 0.25 Gyears gives 80 solar masses swallowed by that hole
since the "big bang", on average.


80 per year. But remember, the universe was denser back then, by a
factor of (1+17)^3.

But the stars needed to feed that hole must be born, and then swallowed.


It doesn't have to be stars.

If it is swallowing gas, the process is much more inefficient since gas
heats up... and stops the process.


It doesn't have to be gas. Maybe primordial black holes coalesced.

I suppose that at z=100 with CMB temperatures over 270K star formtion is
not really possible isn't it?

Let's assume that at 135K (z = 50) star formation could begin.
That is 50 Million years after the "bang".

That leaves us with only 200 million years to build that QSO. That means
100 stars per year in average, one each 52 hours...


Again, it doesn't have to be stars. Also, several smaller black holes
could have merged. Calculate (1+17)^3. Almost 6000. A very different
environment.

P.S. The light from the quasar should be affected y this "star rain", at
least it should oscillate when a new star is swallowed. Do we see that?


Again, you are assuming a specific model, based on essentially no
information.