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Fraser
2005-Apr-14, 04:25 PM
SUMMARY: Astronomers from the Australian National University think they've found one of the earliest stars to have formed in the Universe. It's called HE 1327-2326, and it has the lowest levels of iron ever found in any star. Heavier elements like iron only form inside stars, so HE 1327-2326 could have formed before successive generations of stars had seeded the Universe. This star was observed using the Japanese Subaru 8-m telescope, and found to be twice as iron poor as the previous record holder.

View full article (http://www.universetoday.com/am/publish/earliest_stars_found.html)

What do you think about this story? Post your comments below.

antoniseb
2005-Apr-14, 04:43 PM
I would really have liked for this article to have spelled out just how low the Iron (and other heavy elements) in this star were compared to the sun, and perhaps to get a sense of how wide is the variation that stars have on their elemental abundances. Also, the High in Strontium issue was just dropped as a passing reference, but Strontium is above Iron, and really requires an explanation.

While I'm complaining about lack of detail, what spectral type was this star? is it an M-Dwarf? I'm guessing the only other choice is K9, since I don't think any other star could be main sequence this long.

One last point is the argument in the article is that this star must have been formed shortly after the big bang, but we ran an article recently about the discovery of a pristine cloud starting to form a brand new galaxy relatively nearby. I'm not saying this star has to be new, but it doesn't strictly have to be old.

GOURDHEAD
2005-Apr-14, 05:27 PM
I assume from the level of detail of the spectral analysis (and its identity tag) that this star is in the MW or a nearby satellite galaxy. How old is the MW relative to the oldest known galaxies?

I'm not saying this star has to be new, but it doesn't strictly have to be old. A very good point. Also, it raises the question of how long a pristine cloud can exist within (or wander into) a galaxy and remain free of contamination from all the star bursting taking place within its home galaxy.

antoniseb
2005-Apr-14, 05:44 PM
Originally posted by GOURDHEAD@Apr 14 2005, 05:27 PM
How old is the MW relative to the oldest known galaxies?

The Milky Way is generally thought to have formed very early. There appear to be stars in it that are a little over 13 billion years old.

how long a pristine cloud can exist within (or wander into) a galaxy and remain free of contamination from all the star bursting taking place within its home galaxy.
This cloud was galaxy sized and look like it might be forming a new galaxy for the first time, now. A cloud in a galaxy can't stay clean long.

wstevenbrown
2005-Apr-14, 07:09 PM
The source document isn't particularly strong, either:

arxiv.org/astro-ph/0503021

The metallicity is given as -5.4, but the error range includes the previous record-holder at -5.2. The mass and distance are poorly constrained. You may make your own guess as to spectral type-- not even the surface temp was given with certainty. I'll read this again after I calm down, but I think these guys published too early. S :(

wstevenbrown
2005-Apr-14, 07:46 PM
Re-reading didn't help-- too much soup, not enough oysters. Spectrum was near-UV (ca.300-700nm).

Going strictly by their temp guesstimate spectral type is G2p. A better guess would be K8 with recent planetary cannibalism (hey, if they can do it, so can I).

No rotation speed data, no magnetic field data. S

antoniseb
2005-Apr-14, 07:53 PM
Originally posted by wstevenbrown@Apr 14 2005, 07:46 PM
No rotation speed data, no magnetic field data.
So it has about 2 or 3 part per million as much Iron as the Sun has in it's photosphere.

I suspect that somewhere these guys will be able to get some good instrument time to get more details about this star. Maybe we'll have to wait for the next generation insturments (30-meter class) to actually get good data.

StarLab
2005-Apr-14, 09:11 PM
Finally, something for the Aussies of the forum to be proud of! :lol:

Mr. Smartypants gamer guy
2005-Apr-14, 09:24 PM
k... now can we find a star without irn or do we have 2 just look inside a blk hole and try and fish one out if there arn't any more..?

Greg
2005-Apr-15, 08:27 AM
What can be said for certain is that they found a very metal poor star. It likely is a second or third generation star, but it is equally likely that is a few billion rather than 13 billion years old. I do not see why it couldn't have formed from a primordial cloud left undisturbed until well after the big bang. Just another example of drawing conclusions after making assumptions based on real but incomplete data.

wstevenbrown
2005-Apr-15, 03:50 PM
This quote is from a recent pub describing metallicity in nearby disk stars :

From arxiv.org/asrto-ph/0504316 “For ages greater than 3 Gyr, our results agree with the other recent studies that there is almost no correlation between age and metallicity,”

Ipso res loquatur. Steve

GOURDHEAD
2005-Apr-15, 05:01 PM
“For ages greater than 3 Gyr, our results agree with the other recent studies that there is almost no correlation between age and metallicity,” I wonder what the average metallicity is earlier than 3 gigayears ago. This is an unusually strong and anti-BB statement. Also, assuming that metallicity has increased since 3 gigayears ago, Earth life should be some of the earliest thus explaining the dearth of "them".

antoniseb
2005-Apr-15, 05:14 PM
Originally posted by wstevenbrown@Apr 15 2005, 03:50 PM
“For ages greater than 3 Gyr, our results agree with the other recent studies that there is almost no correlation between age and metallicity,”
I would think that since the main star-forming era in our galaxy ended about 5 billion years ago, and that hot supernova generating stars from that era would have all exploded by 3 billion years ago, that age should not be much of a factor in stellar metalicity during the last three billion years so nearly as much as location would be. Stars born from clouds heavily contaominated with Supernova debris should produce more highly metalic stars than clouds further out from the center of the galaxy.

wstevenbrown
2005-Apr-15, 05:53 PM
age should not be much of a factor in stellar metalicity during the last three billion years so nearly as much as location would be

Just so. Discerning the history of the gas clouds would be, IMHO, the primary motivation for finding these statistical outliers. By their spatial distribution and their peculiar motions, LoM stars will tell us about recent galactic weather. Best regards-- Steve

Greg
2005-Apr-15, 07:50 PM
My understanding was that this star is not within our galaxy. If it is not then all bets are off on how old it is, since as we have seen some nearby galaxies that are newly forming even 10 billion years after the BB. IF the star is within the galaxy then it is likely as old as they say it is, but this wasn't what I was led to believe.