Earliest Rocky Planets: Timeframe & Info

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Discussion Overview

The discussion revolves around the timeframe for the formation of rocky planets, exploring when such planets could have first existed in the universe. Participants consider various astronomical models, the role of metal-rich stars, and the implications of different stellar populations on planet formation.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants suggest that rocky planets could form two to three billion years after the Big Bang, allowing for sufficient metal enrichment from supernovae.
  • Others argue that any definitive answer is highly suspicious, questioning the basis for measuring time and what constitutes a "definitive" timeframe.
  • One participant references estimates that Population I stars, which are metal-rich, could have formed as early as 9 billion years ago, with the oldest being 6-9 billion years old.
  • Another participant mentions the existence of a gas giant, Methuselah PSR B1620-26B, which is estimated to be 12.7 billion years old, speculating that rocky planets may have formed around 2 to 3 billion years later.
  • There is a discussion about whether metals are necessary for the formation of "rocks," with some clarifying that any element beyond hydrogen and helium is considered a metal in astronomical terms.
  • Some participants propose that Population II stars, which are metal-poor, could also potentially host rocky planets, suggesting that the timeline may not be limited to Population I stars.
  • One participant indicates that the question is not for an astronomy project but rather for understanding the earliest possible time for a planet to exist that could support life, linking it to broader historical research.
  • There is a mention of evolving perspectives, with some suggesting that newer evidence may indicate rocky planets could have formed around 3 to 4 billion years after the Big Bang.

Areas of Agreement / Disagreement

Participants express a range of views, with no consensus on a definitive timeframe for rocky planet formation. Some estimates suggest a timeframe of 6 to 7 billion years after the Big Bang, while others propose newer thinking may indicate 3 to 4 billion years. The discussion remains unresolved with multiple competing views.

Contextual Notes

Participants note the dependence on definitions of "rocky" and "metals," as well as the uncertainty surrounding the earliest conditions necessary for planet formation. The discussion also highlights the complexity of measuring time from different cosmological events.

andygee
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I'm looking for a more or less definitive answer for the earliest time when rocky planets could form. I saw one thread in this forum that addressed this, but there was no resolution. My guess is two to three billion years from the start to allow for several generations of supernovae to put out enough metal to allow metal-rich protoplanetary disks. Anyone have any hard info?

Thanks --

--Andygee
 
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andygee said:
I'm looking for a more or less definitive answer for the earliest time when rocky planets could form.
You won't get one. Any claimed definitive answer would be highly suspicious.

Anyway - where are you measuring time from?
From when time separated out?

What would you recognize as "definitive"?
 
Simon Bridge said:
You won't get one. Any claimed definitive answer would be highly suspicious.

Anyway - where are you measuring time from?
From when time separated out?

What would you recognize as "definitive"?

I'd be happy to take a consensus guess of cosmologists who have considered the question.

I'm measuring time from the big bang.

Thanks --

--andygee
 
post number 3105934 by Deuterium2H had something about this.

https://www.physicsforums.com/showthread.php?p=3105934#post3105934

I have seen several estimates that Population 1 (metal-rich) stars could have formed as early as 9 billion years ago. In this post however, Deuterium2H merely says that the oldest Pop 1 stars are "6-9 billion years" old.

Planets have been found orbiting a Pop 11 (metal-poor) star--there was an MPIA announcement in 2011 about that--but these would presumably not be ROCKY planets.

I think Deuterium2H knows what he is talking about and since I do not have an authoritative peer-review source for you I would only suggest that you write a PM to him and ask him for a source on the oldest Pop 1 stars. If you are lucky he will refer you to some pre-print at arxiv.org and give a link. If he just gives you an author name, journal and publication year, then come back here and ask. People will help find an online copy.

It's an interesting question.
 
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Another factor that may help in an estimate. One of the oldest Jupitor like planets Gas giants. Is Methuselah PSR B1620-26B.
The estimates for this planet is 12.7 billion years ago. Keep mind this is a gas giant. So is its companion planet in this system.
How much later was their enough heavier material to form rocky planets I would have no idea. If I were to guess it would be around 2 to 3 billion years later. However that's a very rough guess based solely on the previous gas giant
 
Mordred said:
http://www.lanl.gov/science-innovation/science-features/planetary-formation-theory.php

here is one related article. Marcus if you target the 10% metal percentage mentioned in the above. That may help narrow down the age.
This is kind of a fun question to answer

http://www.space.com/17441-universe-heavy-metals-planet-formation.html

according to the above the conditions needed may be earlier than we think as gas giants also may also require heavy metals

Lol I posted the above in the wrong thread unfortunetely I can't delete it from my phone ah well.
 
Hmmm... do you need metals to have "rocks"?
Anyway - question asked for metals.

Related discussion:
http://cosmoquest.org/forum/showthread.php?93425-Oldest-possible-Population-1-(high-metallicity)-stars

... the kinds of planets under consideration would form along with pop I stars right? So the question would be "how long to pop I stars?" The oldest pop I stars are supposed to be 5-6 billion years old... that would be a pretty definitive time frame despite my earlier comments. So... somewhere between 4.5 and 7billion years ago?
Is that a narrow enough range ... subtract from 13.77 billion years to get time from big bang... looks like rocky planets may have first formed roughly half the Universes lifetime ago.

NGC 118 mentioned in the (above) link.
The age of NGC 118 stars.
 
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Simon Bridge said:
Hmmm... do you need metals to have "rocks"?
You seem confused. Any element other than hydrogen and helium is metal, so Yes, you need metals to have "rocks".
On a more relevant note, can we really rule out Pop II? They are metal poor but not metal free Pop III. Even with one in billion chance, they should have rocky planets before Pop I came to existence.
 
You seem confused. Any element other than hydrogen and helium is metal, so Yes, you need metals to have "rocks".
Oh right - I was thinking in terms of chemistry, not astronomy.
http://en.wikipedia.org/wiki/Periodic_table_(metals_and_nonmetals )
http://chemistry.about.com/od/elementgroups/a/metalslist.htm
On a more relevant note, can we really rule out Pop II? They are metal poor but not metal free Pop III. Even with one in billion chance, they should have rocky planets before Pop I came to existence.
... and a big gas giant can have "metallic hydrogen" ... probably dosn't count ;)
I think that is a call for OP as it depends on what the information is wanted for.

I have encountered this sort of question in the context of SciFi - where the interest is in ancient spacefaring civilizations ... and from theists in the context of the argument from improbability.

If we interpret the question as asking for the literal earliest possible planetary formation out of material that includes elements other than hydrogen and helium then we would certainly not exclude pop II stars. But I think the term "rocky" needs a bit more than that.
 
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  • #10
OP speaks

The information is not requested as part of an astronomy project. Specifically, I'm looking for the earliest likely time for a planet to exist with the possibility of evoloving some form of life; I'm making the leap that that calls for a "rocky" planet. It's one of a list of dates I'm researching that includes things like adult lactose tolerance, invention of the brick, formation of our solar system (that's pretty well known of course) and a bunch of other items.

I must say everyone has been very helpful. If I understand what I'm reading, "conventional" thinking had it around 6 or 7 billion years FBB; newer thinking and evidence may have it as 3 to 4 billion years FBB. If that's more or less the case, then I'm happy.

--andygee
 
  • #11
Those estimates I would consider reasonable.
 

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