Murchison - oldest meteorite?

[Merlin66 (Ken)]

https://www.abc.net.au/news/science/...orite/11863486

[GrahamL]

Good read Ken ,, thats a hard one to buy ,, likely got a little harder

[Peter Ward]

As Sagan was fond of saying, extraordinary claims require extraordinary evidence. Seems their sample of one differs from other data...

"In the new study, scientists used the UK Infrared Telescope (UKIRT), the Very Large Telescope (VLT) and the Subaru telescope to carry out the most complete survey ever made of star-forming galaxies at different distances, with around ten times the data of any previous effort. With the range of distances, the time taken for the light to reach us means that we see identically selected galaxies at different periods in the history of the universe, so we can really understand how conditions change over time.

By looking at the light from clouds of gas and dust in these galaxies where stars are forming, the team are able to assess the rate at which stars are being born. They find that the production of stars in the universe as a whole has been continuously declining over the last 11 billion years, being 30 times lower today than at its likely peak, 11 billion years ago"

[alocky (Andrew lockwood)]

What are you disputing, exactly Peter? The paper describes a grain of silicon carbide with an estimated age of 7 billion years. Nothing extraordinary here, we’ve always believed that the solar system was second generation at least.
The error bars on the estimate are admittedly quite large, but the technique has been validated at shorter timescales. The paper makes no claims other than the estimate of the age of a dust grain in the meteorite, so I’m curious as to why you’ve invoked Sagan on them?
Cheers
Andrew.

Originally Posted by Peter Ward

As Sagan was fond of saying, extraordinary claims require extraordinary evidence. Seems their sample of one differs from other data...

"In the new study, scientists used the UK Infrared Telescope (UKIRT), the Very Large Telescope (VLT) and the Subaru telescope to carry out the most complete survey ever made of star-forming galaxies at different distances, with around ten times the data of any previous effort. With the range of distances, the time taken for the light to reach us means that we see identically selected galaxies at different periods in the history of the universe, so we can really understand how conditions change over time.

By looking at the light from clouds of gas and dust in these galaxies where stars are forming, the team are able to assess the rate at which stars are being born. They find that the production of stars in the universe as a whole has been continuously declining over the last 11 billion years, being 30 times lower today than at its likely peak, 11 billion years ago"

[Peter Ward]

Originally Posted by alocky

What are you disputing, exactly Peter? The paper describes a grain of silicon carbide with an estimated age of 7 billion years. Nothing extraordinary here, we’ve always believed that the solar system was second generation at least.
The error bars on the estimate are admittedly quite large, but the technique has been validated at shorter timescales. The paper makes no claims other than the estimate of the age of a dust grain in the meteorite, so I’m curious as to why you’ve invoked Sagan on them?
Cheers
Andrew.

They also claim there was a massive peak in star formation some 7 billion years ago:
"In order to explain our age distribution, where we have many more younger grains that we would otherwise expect, we have to explain this by this dust forming from more stars than normal," he said.

"We came to the conclusion that about 7 billion years ago there must have been an episode of enhanced star formation, probably about 50 per cent more stars formed than normal."

vs the 11 billion year UKIRT figure. Their data is thin and assumptions hardly proven. I remain sceptical as a result.

[alocky (Andrew lockwood)]

Ahh - definitely worth reading the actual paper on the PNAS site- the mild SFR they talk about is localised. It’s a very nice bit of work, and there is a link in the abc article.
Cheers!

Originally Posted by Peter Ward

They also claim there was a massive peak in star formation some 7 billion years ago:
"In order to explain our age distribution, where we have many more younger grains that we would otherwise expect, we have to explain this by this dust forming from more stars than normal," he said.

"We came to the conclusion that about 7 billion years ago there must have been an episode of enhanced star formation, probably about 50 per cent more stars formed than normal."

vs the 11 billion year UKIRT figure. Their data is thin and assumptions hardly proven. I remain sceptical as a result.