Australian astronomers discover oldest known star in universe

13.6B years old! Just 200 million years after the BB!

Yousuf Khan

Australian astronomers discover oldest known star in universe | Science
| theguardian.com
http://www.theguardian.com/science/2...ar-in-universe

In sci.physics Yousuf Khan wrote:
13.6B years old! Just 200 million years after the BB!

Yousuf Khan

Australian astronomers discover oldest known star in universe | Science
| theguardian.com
http://www.theguardian.com/science/2014/feb/10/
australian-astronomers-discover-oldest-known-star-in-universe

Somewhere else the youngest galaxy has also been spotted.

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File:Radiosonde_Satellite_Surface_Temperature.svg

Dear Yousuf Khan:

On Monday, February 10, 2014 11:32:05 AM UTC-7, Yousuf Khan wrote:

13.6B years old! Just 200 million years after
the BB!

And even it was second generation, being a remnant of a 60 solar mass supernova.

David A. Smith

On 10/02/2014 2:23 PM, dlzc wrote:
Dear Yousuf Khan:

On Monday, February 10, 2014 11:32:05 AM UTC-7, Yousuf Khan wrote:

13.6B years old! Just 200 million years after
the BB!

And even it was second generation, being a remnant of a 60 solar mass supernova.

David A. Smith

And you'd have thought that such a star would be showered with the iron
made in that original supernova, but it seems to be pretty poor in iron.
If the supernova was one of the 1st generation stars, we can assume that
maybe it formed a million years after the BB, and then at 60 solar
masses, it should only last about 400,000 years before it blows. So
we're at 1.4 million years after the BB, and then that leaves another
198.6 million years for the supernova debris to pollute the next
generation of stars. How far can supernova debris travel in 198.6
million years?

Yousuf Khan

In article ,
Yousuf Khan writes:
And you'd have thought that such a star would be showered with the iron
made in that original supernova, but it seems to be pretty poor in iron.

The article is at
http://www.nature.com/nature/journal...ture12990.html
(You'll need a subscription or pay to read the full article, but the
abstract is public and quite informative.)

The spectra show an iron abundance 10^-7.1 of solar. Calcium is
also low, but magnesium and carbon are relatively high at -3.8 and
-2.6 in the log respectively. That means the SN created good amounts
of magnesium and carbon but relatively little iron and calcium.
There are apparently a variety of Pop III SN models available. This
observation -- the first observational test so far as I know --
agrees with mid-range masses that form a black hole. There is also a
suggestion that the energy release is relatively low.

How far can supernova debris travel in 198.6
million years?

I think your age for the SN is too early: z=20 or 180 Myr after the
Big Bang would be more typical. Nevertheless, SN debris travel fast,
and galaxies were small back then. It's useful to remember that
1 km/s is 1 pc/Myr, so a typical speed of 1000 km/s (appropriate for
low energy SN seen today) is 1 kpc/Myr. That means 1 Myr is easily
enough time to pollute a whole galaxy. The article says the
"instantaneous gas mixing" model is doubtful, but that depends on
assumptions that may not be true.

It's also useful to remember that the age estimates don't come
directly from the observations but are more or less made up to be
consistent with standard cosmology. If cosmology changes, the age
estimates would change too.

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On 10/02/2014 2:23 PM, dlzc wrote:
Dear Yousuf Khan:

On Monday, February 10, 2014 11:32:05 AM UTC-7, Yousuf Khan wrote:

13.6B years old! Just 200 million years after
the BB!

And even it was second generation, being a remnant of a 60 solar mass supernova.

David A. Smith

There's another article:

SM0313: Oldest Known Star Discovered | Astronomy | Sci-News.com
http://www.sci-news.com/astronomy/sc...tar-01752.html

"The astronomers also measured the abundance of carbon in SM0313, and
found that this element was in much higher supply – more than 1,000
times greater than iron."

So it sounds like the first gen star was strong enough to spew out its
carbon in its outer layers, but not not strong enough to push out its
iron in its inner-most layers. It's likely the whole iron core was
swallowed by the resultant blackhole. And that any iron in that got into
the second generation star was as a result of endothermic processes at
the explosion.

Yousuf Khan