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Horizon- Cosmic Dawn: The real moment of Creation


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On last night and available on iPlayer.

Very interesting. For the first 100 million years or so after the Big Bang, the universe was a dark place- no light just hydrogen atoms scattered randomly accross space. Things then started to happen and massive stars formed, so big and so hot that their life was measured in millions of years. Susbequent Hypernovas started to scatter the heavy elements that made the universe as we know it possible and also started to clear the fog of atoms.

 

Etc.

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2 hours ago, Gasman said:

 

Yes, the massive stars did the Elden Tyrell Blade Runner speach to Roy Batty bit- The light that burns twice as bright burns half as long" and subsequently blew up in hypernovas. These explosions created and spread the universal building block heavy elements such as iron, carbon, oxygen and also cleared the hydrogen atom fog that was causing the cosmic dark age. The hydrogen molecules coalesced into smaller stars and galaxies and the universe as we know it started to grow.

An interesting fact for those considering spectroscopy is that the first or second generation stars as we know them were very low in iron. The younger a star, the more iron is present. A star has been found so low in iron that it is estimated to be from only a few billion years after the Big Bang.

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21 minutes ago, Swoop1 said:

An interesting fact for those considering spectroscopy is that the first or second generation stars as we know them were very low in iron. The younger a star, the more iron is present. A star has been found so low in iron that it is estimated to be from only a few billion years after the Big Bang.

More generally the earliest stars are short of all "metals" ( in astronomy all elements other than Hydrogen and Helium).  More recently formed stars have more "metals".

The temperature of the stars photosphere determines if and when a particular element shows up in the spectra.

Regards Andrew

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I thought this was an excellent episode, just finished watching the recording. Not dumbed down and plenty of facts. Perhaps the S@N could take a leaf out of this book! Mind you, S@N has less time to expand on a topic.

What I don't understand, though, is that Stefan's star is only a 2nd generation star, and therefore must be very old, and therefore, I assume, very distant. Yet it is supposed to be in our galaxy.

Ian

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3 hours ago, The Admiral said:

and therefore, I assume, very distant.

If its distant it is old due to the time the light takes to get here but the inverse is not true. It can be old but next door we just see it as it it was a "few" light years ago.

Regards Andrew

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1 hour ago, andrew s said:

If its distant it is old due to the time the light takes to get here but the inverse is not true. It can be old but next door we just see it as it it was a "few" light years ago.

Regards Andrew

But if that is so, then surely the star itself must have lived for many billions of years. Do stars live that long?

Ian

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14 minutes ago, The Admiral said:

But if that is so, then surely the star itself must have lived for many billions of years. Do stars live that long?

Ian

Yes, the life of a star basically depend on it zero age mass. A star with 0.1 the mass of the Sun can live for 1000s of Billions of years.

Regards Andrew 

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1 minute ago, andrew s said:

Yes, the life of a star basically depend on it zero age mass. A star with 0.1 the mass of the Sun can live for 1000s of Billions of years.

Regards Andrew 

Ah, yes, I should have known that!! Thanks for the reminder!

Ian

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