>But observations using the world’s largest radio telescope are casting doubt on this long gestational period. Researchers have zoomed in on a prestellar core in a giant gas cloud—a nursery for hundreds of baby stars—and found the tiny embryo may be forming 10 times faster than thought, thanks to weak magnetic fields.
I'm sure this has been taken into account already (by actual scientists much smarter than me) but, how do we know it isn't dark matter causing the collapse to happen faster than thought? Seems like a reasonable question to me. Lack of gravitational lensing?
(edit:) Also
>thanks to weak magnetic fields ... Zeeman effect etc
This is a bit questionable to me. I understand the Zeeman effect, or thought I did, but I don't understand how it can be thanks to a "weak" magnetic field.
pdonis
> how do we know it isn't dark matter causing the collapse to happen faster than thought?
The average density of dark matter is way too small. It's significant on the scale of a galaxy because it doesn't clump, so its density is basically the average density everywhere (denser towards the center and less dense further out, but still of the same rough order of magnitude), instead of being isolated clumps surrounded by huge expanses of empty space, as with ordinary matter. But on the scale of a single stellar system the density of dark matter is so small that its effect on the dynamics is negligible.
Good explanation of low density of dark matter as measured by squirrels.
37
This is a excellent response! Thank you!
dtgriscom
The observations didn't measure the speed of the collapse; they measured the strength of the magnetic field which guides models of the collapse. Magnetic fields tend to slow the gas collapsing, so finding that the fields were lower than expected decreases the expected time of collapse.
37
Thank you! This is also a great response! Now I'm wondering how they measure magnetic fields. But of course I'm sure there's about a million youtube videos explaining that.
>Magnetic fields tend to slow the gas collapsing, so finding that the fields were lower than expected decreases the expected time of collapse.
I think this part might be backwards, wouldn't it increase the expected time of collapse, which is to say stars may form faster than thought?
(edit: no, I'm just tired and wrong, yet again...)
antognini
At a very simplified level, in these kinds of astrophysical contexts you can kind of think of magnetic field lines as strings, and the particles in the gas are forced to follow the strings. The stronger the field, the more closely the particles have to follow those strings. So if the magnetic field is large, they can have the effect of redirecting particles from where they otherwise would go due to gravitational collapse, and slow the process down.
simonh
They explain the measurement approach in the article. The Zeeman effects occurs when spectral absorption lines 'split' due to the influence of magnetic fields. They measure this effect at radio wavelengths.
37
This led me to thinking, how do we determine the age of the sun? I would have thought some radio spectrometry, but according to NASA[0]:
>We look at the age of the whole solar system, because it all came together around the same time.
>To get this number, we look for the oldest things we can find. Moon rocks work well for this. When astronauts brought them back for scientists to study them, they were able to find out how old they are.
>researchers say they’ve finally pinpointed the exact age of the Moon
Hmm, sounds dubious, but I will read on. A short while later it leads me to the paper[0] and I spend a few more minutes on that, finding myself asking: how do we know the zircon fragments aren't from a meteor that is much older? Surely all the fragments came from approximately the same area, yes? Or maybe not?
But nah, these knowledgeable astronomers must have already thought of all this stuff.
Astronomy is just filled with rabbit holes I guess.
> how do we know the zircon fragments aren't from a meteor that is much older?
Radiometric dating tells you when the sample you are dating last solidified. Of course the atoms in the sample themselves existed before that, but that doesn't matter for radiometric dating since what is being measured is not the age of the atoms but the time the sample, the piece of rock you're analyzing, last solidified.
> Surely all the fragments came from approximately the same area, yes?
Um, yes, since the Apollo 14 astronauts only collected samples from a very small area.
> nah, these knowledgeable astronomers must have already thought of all this stuff.
Yes, in fact, they have, plus a lot more things that haven't even occurred to you.
kjeetgill
> Yes, in fact, they have, plus a lot more things that haven't even occurred to you.
My charitable reading of the parent post is that asking these obvious questions first, then hunting down the answer is an incredible way to learn how "we" know things.
I think it's a perfectly fair way to note that the poster doesn't have the complete story yet.
37
Thank you, kjeetgill, for understanding my ignorance and line of questioning.
whatshisface
It's a tragedy what Just Asking Questions has done to just asking questions.
jacquesm
> Yes, in fact, they have, plus a lot more things that haven't even occurred to you.
Exactly. Like that comment about the JWST last week that was wondering why they didn't bring down the number of single-points-of-failure. Backseat driving at its best.
jasonwatkinspdx
This website's favorite thing is sophmoric armchair contrarianism, as if people who have spent their entire lives dedicated to a topic need some tech industry clown to come along and show them something after 5 seconds thought. It gets very tiresome but I've learned to accept this place will always be like that, to some extent because the example PG set.
37
I feel that after this comment, and it's parent, and it's parent's parent, I should address the topic.
No, I am not the smartest person here. I understand that. A few days ago I asked a question and people told me to get more involved in HN with commenting and posting and such. People also warned about gatekeeping. I had seen it talked about with regards to HN before, but never really noticed it. So then I try to get more involved and now I understand.
I am not trying to be an "armchair contrarian" or "backseat driver" or anything of the sort. I am just wondering out loud on the internet. And I don't think I was JAQing off either.
(and btw jason, I'm not a tech industry clown, I'm just a nobody clown.)
jasonwatkinspdx
Hey I want to be clear I was just talking about a meta trend, not specifically attacking you. Sorry it clearly read that way. My apologies.
pdonis
> I am not trying to be an "armchair contrarian" or "backseat driver" or anything of the sort.
Statements like these...
> Hmm, sounds dubious, but I will read on.
> But nah, these knowledgeable astronomers must have already thought of all this stuff.
...do not lend support to your claim here.
Not knowing much about an area of science on which many people have spent a lot of time and effort is fine. Being dismissive about it without knowing much about it is not.
37
Hmm, okay, I think I understand.
For the record, the 'sounds dubious' comment was directed at the claim that we know the "exact" age of the moon. It is more a criticism of shoddy journalism than a statement of my knowledge of the subject. I know enough to know that we cannot pinpoint the "exact" age of the moon.
And the 'knowledgeable astronomers' claim was almost more of a meek confession that idk wtf I am talking about. It was not meant sarcastically at all. I know a little, but not as much as people who went to school and do this stuff professionally.
Everyone, please note: I'm not trying to back-peddle or make excuses or anything like that here, just explaining my reasoning.
(Edit: but thanks for the criticism, it really does help to see your point of view on these things. This is a discussion board after all.)
pdonis
> the 'sounds dubious' comment was directed at the claim that we know the "exact" age of the moon.
Yes, I agree shoddy journalism is a pain. I never even read the articles, I just look for a link to the actual paper (btw, thank you for providing it).
jasonwatkinspdx
The quality of pop science journalism is absolutely atrocious, but I'm not gonna pretend I know the answer to that problem. It just annoys me a lot.
kfarr
Just wait until you hear how astronomers date the approximate age of rabbit holes…
philipov
> Astronomy is just filled with rabbit holes I guess.
No wonder some cultures think Rabbits live on the moon.
politician
Isn't it kind of weird to use the Moon to benchmark the age of the solar system when it's well known that the Moon formed after another body collided with the Earth? The Moon is younger than the Earth.
treeman79
Moon is a mix of earth and theia. So is Earth. So sort of like a strawberry banana smoothie in two cups.
Core of Theia sunk into Earth and there is some recent imaging showing what may be the second core.
I assume it’s because the Moon is geologically inactive and thus the rocks we got from the surface are expected to be essentially as old as the Moon itself.
pdonis
Not to benchmark, precisely, but to give a lower limit on the age that will likely be longer than any other lower limit we could obtain at our current or near future level of technology.
vlovich123
If Theia is older than the Earth, then wouldn't the Moon also be older?
politician
AIUI, the heat of the collision would've melted everything that wasn't already molten. Any "age" information would be lost as the system cooled. At least, that's my understanding from playing with Universe Sandbox.
vlovich123
That would only be the case for the piece that collided though right? The side that wasn’t part of the collision should have retained its age information. Also, presumably Theia didn’t bounce off but just merged with the moon being formed from the piece of Earth on the opposite side from the collision that got ejected, right? So at most half the moon surface should be from the collision and half of it should have the age of the Earth?
peter303
There was a hardcore "Revive Arecibo" workgroup at two recent astronomy conferences. That telescope made important data contributions up to the end, despite its age. Alas, probably a pipe dream, since NASA/NSF has limited funding for all the fantastic stuff in the pipeline already.
UncleOxidant
Maybe there's also a realization that the location isn't ideal in a time of increasing hurricane activity due to climate change?
glennonymous
Not a scientist. But if this is true, would it imply that A) the universe is younger than we thought, or B) there was a much longer time between the Big Bang and the formation of the first stars? Seems to have very major cosmological implications.
glennonymous
Upon five more minutes’ consideration, I thought of several reasons why this would probably not imply either of the things I suggested it might imply. But my larger question is: What, if any, would be the larger cosmological implications of this discovery?
tuatoru
Yes, according to this StackExchange answer[1] star formation was thought to take around 10 million years (for low-mass stars - less for big stars).
That would be a rounding error on a reasonably precise and accurate estimate of the age of the universe (which I don't think we have yet.)
As for cosmological/other physical implications, it's a "well, now we know more" result.
Not really. Don't we estimate the age of the universe by estimating how redshifted the CMB is compared to what we would expect given initial conditions?
37
One order of magnitude off doesn't seem too bad of an original prediction
smm11
So I might be able to notice a .00000001 percent change in my lifetime. Cool.
hsnewman
Then again, they may not form 10 times faster than thought.
dr_dshiv
I think I think faster than stars form, right?
bryanrasmussen
The ambiguity of the English language can often be lessened via simple changes, such as: Stars may form 10 times faster than generally thought.
I'm sure this has been taken into account already (by actual scientists much smarter than me) but, how do we know it isn't dark matter causing the collapse to happen faster than thought? Seems like a reasonable question to me. Lack of gravitational lensing?
(edit:) Also
>thanks to weak magnetic fields ... Zeeman effect etc
This is a bit questionable to me. I understand the Zeeman effect, or thought I did, but I don't understand how it can be thanks to a "weak" magnetic field.
The average density of dark matter is way too small. It's significant on the scale of a galaxy because it doesn't clump, so its density is basically the average density everywhere (denser towards the center and less dense further out, but still of the same rough order of magnitude), instead of being isolated clumps surrounded by huge expanses of empty space, as with ordinary matter. But on the scale of a single stellar system the density of dark matter is so small that its effect on the dynamics is negligible.
Good explanation of low density of dark matter as measured by squirrels.
>Magnetic fields tend to slow the gas collapsing, so finding that the fields were lower than expected decreases the expected time of collapse.
I think this part might be backwards, wouldn't it increase the expected time of collapse, which is to say stars may form faster than thought?
(edit: no, I'm just tired and wrong, yet again...)
>We look at the age of the whole solar system, because it all came together around the same time.
>To get this number, we look for the oldest things we can find. Moon rocks work well for this. When astronauts brought them back for scientists to study them, they were able to find out how old they are.
[0] https://spaceplace.nasa.gov/sun-age/en/
Hmm, sounds dubious, but I will read on. A short while later it leads me to the paper[0] and I spend a few more minutes on that, finding myself asking: how do we know the zircon fragments aren't from a meteor that is much older? Surely all the fragments came from approximately the same area, yes? Or maybe not?
But nah, these knowledgeable astronomers must have already thought of all this stuff.
Astronomy is just filled with rabbit holes I guess.
[0] https://www.science.org/doi/10.1126/sciadv.1602365
Radiometric dating tells you when the sample you are dating last solidified. Of course the atoms in the sample themselves existed before that, but that doesn't matter for radiometric dating since what is being measured is not the age of the atoms but the time the sample, the piece of rock you're analyzing, last solidified.
> Surely all the fragments came from approximately the same area, yes?
Um, yes, since the Apollo 14 astronauts only collected samples from a very small area.
> nah, these knowledgeable astronomers must have already thought of all this stuff.
Yes, in fact, they have, plus a lot more things that haven't even occurred to you.
My charitable reading of the parent post is that asking these obvious questions first, then hunting down the answer is an incredible way to learn how "we" know things.
I think it's a perfectly fair way to note that the poster doesn't have the complete story yet.
Exactly. Like that comment about the JWST last week that was wondering why they didn't bring down the number of single-points-of-failure. Backseat driving at its best.
No, I am not the smartest person here. I understand that. A few days ago I asked a question and people told me to get more involved in HN with commenting and posting and such. People also warned about gatekeeping. I had seen it talked about with regards to HN before, but never really noticed it. So then I try to get more involved and now I understand.
I am not trying to be an "armchair contrarian" or "backseat driver" or anything of the sort. I am just wondering out loud on the internet. And I don't think I was JAQing off either.
(and btw jason, I'm not a tech industry clown, I'm just a nobody clown.)
Statements like these...
> Hmm, sounds dubious, but I will read on.
> But nah, these knowledgeable astronomers must have already thought of all this stuff.
...do not lend support to your claim here.
Not knowing much about an area of science on which many people have spent a lot of time and effort is fine. Being dismissive about it without knowing much about it is not.
For the record, the 'sounds dubious' comment was directed at the claim that we know the "exact" age of the moon. It is more a criticism of shoddy journalism than a statement of my knowledge of the subject. I know enough to know that we cannot pinpoint the "exact" age of the moon.
And the 'knowledgeable astronomers' claim was almost more of a meek confession that idk wtf I am talking about. It was not meant sarcastically at all. I know a little, but not as much as people who went to school and do this stuff professionally.
Everyone, please note: I'm not trying to back-peddle or make excuses or anything like that here, just explaining my reasoning.
(Edit: but thanks for the criticism, it really does help to see your point of view on these things. This is a discussion board after all.)
Yes, I agree shoddy journalism is a pain. I never even read the articles, I just look for a link to the actual paper (btw, thank you for providing it).
No wonder some cultures think Rabbits live on the moon.
Core of Theia sunk into Earth and there is some recent imaging showing what may be the second core.
https://www.iflscience.com/environment/fragments-of-the-plan...
That would be a rounding error on a reasonably precise and accurate estimate of the age of the universe (which I don't think we have yet.)
As for cosmological/other physical implications, it's a "well, now we know more" result.
1. https://astronomy.stackexchange.com/questions/156/how-long-d...
Not really. Don't we estimate the age of the universe by estimating how redshifted the CMB is compared to what we would expect given initial conditions?