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+--- Thread: Now we know when the first stars in the universe switched on (/showthread.php?tid=6691)
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Now we know when the first stars in the universe switched on - Phaedrus - 06-28-2021
newscientist.com
Quote:Between 250 and 350 million years after the big bang, cosmic dawn broke. Measurements of six of the most distant galaxies we have ever seen have allowed researchers to make the most precise calculations ever of when the first stars formed.
“Before cosmic dawn the universe was dark and contained only hydrogen clouds, and now of course we are surrounded by all this beautiful cosmic structure and trillions of stars in the night sky,” says Richard Ellis at University College London. “The question is, when did all this begin?”
Ellis and his colleagues picked six of the most distant galaxies we have ever seen, all more than 25 billion light years away. Because light from those galaxies took a long time to travel to us, we see those galaxies as they were billions of years ago, making them a window into the early universe.
The researchers observed these six galaxies with four of the most powerful telescopes on Earth to measure their distances as precisely as possible and determine how old the stars in the galaxies are. Those distant stars are some of the very first stars that ever formed, so their ages tell us the date of cosmic dawn, which the researchers calculated to be around 13.5 billion years ago.
“If we’d have measured the age of one galaxy, sceptics would have said that maybe it’s a special galaxy, but we have six,” says Ellis. “It’s the first meaningful estimate of when cosmic dawn occurred because it’s based on a sizeable population of galaxies.”
None of our current telescopes are powerful enough to observe the first stars directly because they are simply too far away. But Ellis and his colleagues have calculated that given the timing that they found for cosmic dawn, the upcoming James Webb Space Telescope should be able to see them. It is scheduled to launch in November, and the team has already secured time to look for stars beginning to switch on. “We’re now very close to witnessing this dramatic moment directly,” says Ellis.
RE: Now we know when the first stars in the universe switched on - jerry mcmasters - 06-28-2021
Awesome pick-up line.
RE: Now we know when the first stars in the universe switched on - Minimalist - 06-28-2021
You mean it wasn't on the 4th "Day?"
RE: Now we know when the first stars in the universe switched on - Alan V - 06-28-2021
(06-28-2021, 01:15 AM)Phaedrus Wrote: newscientist.com
Quote:Ellis and his colleagues picked six of the most distant galaxies we have ever seen, all more than 25 billion light years away.
How could any galaxies be 25 billion light years away when the universe itself isn't that old?
Quote:From: https://www.u-tokyo.ac.jp/focus/en/press/z0508_00153.html
“From previous studies, the galaxy GN-z11 seems to be the farthest detectable galaxy from us, at 13.4 billion light years, or 134 nonillion kilometers (that’s 134 followed by 30 zeros),” said Kashikawa.
RE: Now we know when the first stars in the universe switched on - Phaedrus - 06-28-2021
That's the great thing about science. Our knowledge is ever expanding.
RE: Now we know when the first stars in the universe switched on - Bucky Ball - 06-28-2021
(06-28-2021, 01:43 AM)Alan V Wrote: How could any galaxies be 25 billion light years away when the universe itself isn't that old?
The universe isn't static.
It is expanding. They're that far away *now*.
Quote:Between 250 and 350 million years after the big bang, cosmic dawn broke.
I wouldn't exactly say that 100 million years either way, is exactly "precise".
RE: Now we know when the first stars in the universe switched on - Aliza - 06-28-2021
Quote:Now we know when the first stars in the universe switched on
We always knew this. It was right after the phrase, "Let there be light."
RE: Now we know when the first stars in the universe switched on - jerry mcmasters - 06-28-2021
(06-28-2021, 02:00 AM)Bucky Ball Wrote:(06-28-2021, 01:43 AM)Alan V Wrote: How could any galaxies be 25 billion light years away when the universe itself isn't that old?
The universe isn't static.
It is expanding. They're that far away *now*.
...so working backwards, how do you get more than 5 billion years?
RE: Now we know when the first stars in the universe switched on - Bucky Ball - 06-28-2021
(06-28-2021, 02:21 AM)jerry mcmasters Wrote:(06-28-2021, 02:00 AM)Bucky Ball Wrote:(06-28-2021, 01:43 AM)Alan V Wrote: How could any galaxies be 25 billion light years away when the universe itself isn't that old?
The universe isn't static.
It is expanding. They're that far away *now*.
...so working backwards, how do you get more than 5 billion years?
The expansion rate is increasing.
https://en.wikipedia.org/wiki/Stellar_age_estimation
RE: Now we know when the first stars in the universe switched on - jerry mcmasters - 06-28-2021
(06-28-2021, 03:11 AM)Bucky Ball Wrote:(06-28-2021, 02:21 AM)jerry mcmasters Wrote:(06-28-2021, 02:00 AM)Bucky Ball Wrote: The universe isn't static.
It is expanding. They're that far away *now*.
...so working backwards, how do you get more than 5 billion years?
The expansion rate is increasing.
So...how old are you saying the universe is exactly? My understanding is the ballpark of 15 billion. (my mistake I had said 5 billion; thinking of just Earth)
RE: Now we know when the first stars in the universe switched on - Bucky Ball - 06-28-2021
(06-28-2021, 03:13 AM)jerry mcmasters Wrote:(06-28-2021, 03:11 AM)Bucky Ball Wrote:(06-28-2021, 02:21 AM)jerry mcmasters Wrote: ...so working backwards, how do you get more than 5 billion years?
The expansion rate is increasing.
So...how old are you saying the universe is exactly? My understanding is the ballpark of 15 billion. (my mistake I had said 5 billion; thinking of just Earth)
I'm not saying. It 'taint my field.
RE: Now we know when the first stars in the universe switched on - Free - 06-28-2021
(06-28-2021, 01:43 AM)Alan V Wrote:(06-28-2021, 01:15 AM)Phaedrus Wrote: newscientist.com
Quote:Ellis and his colleagues picked six of the most distant galaxies we have ever seen, all more than 25 billion light years away.
How could any galaxies be 25 billion light years away when the universe itself isn't that old?
Quote:From: https://www.u-tokyo.ac.jp/focus/en/press/z0508_00153.html
“From previous studies, the galaxy GN-z11 seems to be the farthest detectable galaxy from us, at 13.4 billion light years, or 134 nonillion kilometers (that’s 134 followed by 30 zeros),” said Kashikawa.
How far away they are and how old the universe is are two different things.
Expansion can cause things to move away faster than the speed of light. For example, 6 billion earth years ago that galaxy may have been only 1 billion light years away. But with expansion it moved another 24 billion light years away in only another 7.5 billion earth years (It's more mathematically complex than this but I hope you get the gist.)
Therefore we are not seeing something that is 25 billion earth years old, but only that it is 25 billion light years away.
RE: Now we know when the first stars in the universe switched on - skyking - 06-28-2021
(06-28-2021, 01:48 AM)Phaedrus Wrote: That's the great thing about science. Our knowledge is ever expanding.
A bunch of "how is 25 Billion light years possible? " speculation ensues, but the answer is right here
RE: Now we know when the first stars in the universe switched on - Alan V - 06-28-2021
(06-28-2021, 03:35 AM)Free Wrote: How far away they are and how old the universe is are two different things.
Expansion can cause things to move away faster than the speed of light. For example, 6 billion earth years ago that galaxy may have been only 1 billion light years away. But with expansion it moved another 24 billion light years away in only another 7.5 billion earth years (It's more mathematically complex than this but I hope you get the gist.)
Therefore we are not seeing something that is 25 billion earth years old, but only that it is 25 billion light years away.
So scientists must figure that those distant galaxies were traveling at a certain (increasing) speed away from Earth when the light from them was originally emitted, and so calculated their distance including that speed. So they did not observe galaxies 25 billion light years away, they inferred they were that distant now. I understood the original statement wrong:
Quote:Ellis and his colleagues picked six of the most distant galaxies we have ever seen, all more than 25 billion light years away. Because light from those galaxies took a long time to travel to us, we see those galaxies as they were billions of years ago, making them a window into the early universe.I took that to mean they had seen galaxies 25 billion light years away.
It is still impossible to see light which was emitted any more than around 13.5 billion years ago (edited per Inkubus's comment), right?
RE: Now we know when the first stars in the universe switched on - Inkubus - 06-28-2021
(06-28-2021, 10:42 AM)Alan V Wrote: It is still impossible to see light which was emitted any more than 13.8 billion years ago (the age of the universe), right?
As per the OP there was no light till ~300 million years after, the big bang.
RE: Now we know when the first stars in the universe switched on - Gawdzilla Sama - 06-28-2021
Well, that's God for you, left the room without turning off the lights.
RE: Now we know when the first stars in the universe switched on - Free - 06-28-2021
(06-28-2021, 10:42 AM)Alan V Wrote:(06-28-2021, 03:35 AM)Free Wrote: How far away they are and how old the universe is are two different things.
Expansion can cause things to move away faster than the speed of light. For example, 6 billion earth years ago that galaxy may have been only 1 billion light years away. But with expansion it moved another 24 billion light years away in only another 7.5 billion earth years (It's more mathematically complex than this but I hope you get the gist.)
Therefore we are not seeing something that is 25 billion earth years old, but only that it is 25 billion light years away.
It is still impossible to see light which was emitted any more than around 13.5 billion years ago (edited per Inkubus's comment), right?
Only if the objects were more than 13.5 billion light years away 13.5 billion earth years ago.
We are seeing these farthest objects in the location they were in 13.5 billion light years ago. Then today, by measuring the speed they were moving away from us 13.5 billion years ago, we can fairly estimate the actual distance they would be away from us now.
Remember, what we see there now is not actually there in that location anymore. It has either moved much farther away or has ceased to exist. But the mathematics that we use tells us the rate of expansion and with some calculations that allow for an increased rate of expansion we can fairly determine where that object would be now, despite not being able to see it in it's current location.
RE: Now we know when the first stars in the universe switched on - Gawdzilla Sama - 06-28-2021
I've seen "farthest galaxy" numbers around 33 billion light years. So that was emitted 33,000,000,000 years ago, meaning the object could be 66,000,000,000 light years away by now?
RE: Now we know when the first stars in the universe switched on - Free - 06-28-2021
(06-28-2021, 01:37 PM)Gawdzilla Sama Wrote: I've seen "farthest galaxy" numbers around 33 billion light years. So that was emitted 33,000,000,000 years ago, meaning the object could be 66,000,000,000 light years away by now?
If an object is 13.5 billion light years away, then we are currently viewing it (conceivably) as it appeared 13.5 billion earth years ago. By examining its movement speed today, we are actually seeing it's movement speed as it was 13.5 billion years ago. With some mathematical calculations, they can determine where that object might be in the present time. After all, it had 13.5 billion years of moving away from us.
All we are seeing today is the past from 13.5 billion years ago. It could be 25 billion light years (or more) away from us by now, or not exist at all anymore.
It is conceivable that with a major push from space expansion an object could suddenly disappear from our view if the expansion exceeded the speed of light. Then, perhaps a billion years from now, that object suddenly reappears as its light made it's way to us from it's new location.
RE: Now we know when the first stars in the universe switched on - Gawdzilla Sama - 06-28-2021
Now it's been reported that space can expand faster than the speed of light. (The joke is "nothing can exceed the speed of light and it does.) So there's nothing against space dragging things along with it?
RE: Now we know when the first stars in the universe switched on - Free - 06-28-2021
(06-28-2021, 04:30 PM)Gawdzilla Sama Wrote: Now it's been reported that space can expand faster than the speed of light. (The joke is "nothing can exceed the speed of light and it does.) So there's nothing against space dragging things along with it?
Actually what happens is this;
Let's put Point A and Point B out in space. Now, let's expand the space between them, and let's say the expansion is happening at the speed of light. Point A is being moved to the left, and Point B is being moved to the right. They are moving away from each other at the speed of light, but over a year they are two light years away from each other.
Expansion doesn't really move faster than the speed of light, it just causes objects to move away from each other at the speed of light. If you are going at the speed of light to the left, and someone is going at the speed of light to the right, you will be two light years away from each other in just one light year. You are both moving in opposite directions from each other, traversing a distance of two light years away from each other in just one light year.
Understand?
RE: Now we know when the first stars in the universe switched on - Deesse23 - 06-28-2021
(06-28-2021, 04:30 PM)Gawdzilla Sama Wrote: Now it's been reported that space can expand faster than the speed of light. (The joke is "nothing can exceed the speed of light and it does.) So there's nothing against space dragging things along with it?
The expansion of space itself is not a movement, so it does not violate relativity. Thats why galaxies, far enough, can receed from us iwth speeds >c and thus (never!) be visible. Actually, far in the future, when the last glaxy has moved so far that the space in between us expands with >c, no galaxies will be visible anymore)!
The notion that "nothing can move faster than light" is egregiously wrong. Even you can make "something" faster than light, easily, without violating Einstein: Take a laser pointer (which can be quite powerful by today), point it towards the Moon and start "wagging" it as quick as you can. The "spot" of light on the Moon may move faster than the speed of light* although nothing actually moves at speeds >c. It i just the projection of the laser beam on the surface of the Moon. The photons will all move with c from the laser to the Moon
There is another easy way to do this: Build a conventional oscilloscope (tube based) with a screen sufficiently large so that the given screen size combined with lateral acceleration (x-axis / time) will result in >c.
C= 300.000.000m/s = 300e6 m/s --> a scope with 30cm lateral width and 1ns total x-axis speed will suffice.
*your small angular movement will produce a huge lateral distance at a significantly big distance from Earth
RE: Now we know when the first stars in the universe switched on - Deesse23 - 06-28-2021
(06-28-2021, 04:54 PM)Free Wrote:This is not limited to 2 x c. Given enough space in between two objects at a given expansion rate of space, these objects can move with speeds >>c away from each other.(06-28-2021, 04:30 PM)Gawdzilla Sama Wrote: Now it's been reported that space can expand faster than the speed of light. (The joke is "nothing can exceed the speed of light and it does.) So there's nothing against space dragging things along with it?
Actually what happens is this;
Let's put Point A and Point B out in space. Now, let's expand the space between them, and let's say the expansion is happening at the speed of light. Point A is being moved to the left, and Point B is being moved to the right. They are moving away from each other at the speed of light, but over a year they are two light years away from each other.
Expansion doesn't really move faster than the speed of light, it just causes objects to move away from each other at the speed of light. If you are going at the speed of light to the left, and someone is going at the speed of light to the right, you will be two light years away from each other in just one light year. You are both moving in opposite directions from each other, traversing a distance of two light years away from each other in just one light year.
Understand?
There is no limit to this, no limit at all.
RE: Now we know when the first stars in the universe switched on - Free - 06-28-2021
(06-28-2021, 05:07 PM)Deesse23 Wrote:(06-28-2021, 04:54 PM)Free Wrote:This is not limited to 2 x c. Given enough space in between two objects at a given expansion rate of space, these objects can move with speeds >>c away from each other.(06-28-2021, 04:30 PM)Gawdzilla Sama Wrote: Now it's been reported that space can expand faster than the speed of light. (The joke is "nothing can exceed the speed of light and it does.) So there's nothing against space dragging things along with it?
Actually what happens is this;
Let's put Point A and Point B out in space. Now, let's expand the space between them, and let's say the expansion is happening at the speed of light. Point A is being moved to the left, and Point B is being moved to the right. They are moving away from each other at the speed of light, but over a year they are two light years away from each other.
Expansion doesn't really move faster than the speed of light, it just causes objects to move away from each other at the speed of light. If you are going at the speed of light to the left, and someone is going at the speed of light to the right, you will be two light years away from each other in just one light year. You are both moving in opposite directions from each other, traversing a distance of two light years away from each other in just one light year.
Understand?
There is no limit to this, no limit at all.
I agree, I am just trying to keep it simple for the gist of it rather than go into the snowball effect of an "expansion bubble." I'm just trying to avoid the math and leave that up to guys like you who can run circles around me with it.
RE: Now we know when the first stars in the universe switched on - Gawdzilla Sama - 06-28-2021
(06-28-2021, 05:04 PM)Deesse23 Wrote: The notion that "nothing can move faster than light" is egregiously wrong. Even you can make "something" faster than light, easily, without violating Einstein: Take a laser pointer (which can be quite powerful by today), point it towards the Moon and start "wagging" it as quick as you can. The "spot" of light on the Moon may move faster than the speed of light* although nothing actually moves at speeds >c. It i just the projection of the laser beam on the surface of the Moon. The photons will all move with c from the laser to the Moon
LOL, the light leaving the laser doesn't go faster, the aiming point just changes. With sharp enough eyes you could observe this.