7 ms·

Astronomers just confirmed the most ancient galaxies ever observed

76 points by cheinyeanlim 4y ago

ggm 4y ago
One of the things which helps with "how far" is time: if you can wait until something has rotated a bit, then you get sideways distance to do triangulation. (because the path of the earth in orbit defines a wider baseline so two observations at the equinoxes (for instance) give you maximal distance. If you can wait even longer you get other rotational movements but some of those "longers" are very long.) As a student in the amateur astronomy space (I didn't progress far) I was quite purturbed by the main sequence "colour == size" thing and the parallel lanes of "colour == distance" and "colour == age" It felt like cheating to put 3 qualities into play, all of which could undermine the others. I'm not even really sure I think you can have two. Maybe there is some unstated principle that all dull things are old and all red dull things are old and far away, but if you also think all old red dull things are huge but all you got was "it's red" then it's feeling shakey. Pick one.
- defrost 4y ago
  Triangulation doesn't especially add much (or, in fact anything at all) when the base of the triangle is 2 AU across (the diameter of the Earth's orbit, or roughly 16 light minutes) and the long axis of the triangle is 13.4 billion light years.
  - ggm 4y ago
    What about for discounting the false positives of objects which may be "closer in the mirror than they appear" ? I would have thought the differential to movement and the accuracy of a 2AU baseline was meaningful there. And occultation, both of which comes from study of other objects of known distance, which are within the limits of resolution for a 2AU baseline. I believe the GAIA mission pushed to 10-6 arcsec. I can't find a more recent limit online, love to know what it is. (copied from https://astronomy.swin.edu.au/cosmos/t/trigonometric+parallax https://astronomy.swin.edu.au/cosmos/t/trigonometric+paralla...)
    - defrost 4y ago
      These are fair points .. but not especially so for objects this distant. Given what you know from your interest already you might like to, say, work out at what distance objects appear to essentially fixed in position when viewed from either end of a 2 AU baseline. Having a background wallpaper of 'fixed' objects that can be occluded helps to inform us about the closer occluding objects .. but triangulation doesn't assist in depth sorting all the distant objects that appear fixed. My comment above assumed (perhaps incorrectly) that you were referring to the title topic and implying that our motion about the sun was enough to determine the distance to these far objects as the JWT moved through a few orbits.
      - ggm 4y ago
        No, I did make that assumption. I didn't realize the limits to VLBI inside our own contextual frame(s) of reference. Getting more AU into things would be nice but I suppose there are other, nicer, cheaper things we can do. And if the main sequence and redshift thing is good enough, then in the end "how far away it is" can remain defined by that, rather than by geometry.
        canadianfella 4y ago
        badcppdev 4y ago
        Replying to you and defrost here. I think the solar system moves ~48 AU around the galactic centre every year. And the Milky Way is doing ~117 AU per year. (Using google for calculations) So maybe that combined with space based telescopes helps to make the parallax method more useful over time. Depending on vectors, etc.
- googlryas 4y ago
  It's not color == distance though, it is color + brightness. Maybe there is some unknown principle at play but you could say that about anything which is not directly measurable, for example how old the earth is. But, it's the best we've got so far, and it does provide seemingly reasonable results that also align with parallax measurements when parallax is within the usable range.
- porcoda 4y ago
  "Colour" is oversimplifying it a bit. We're usually concerned with the distribution of light received with respect to wavelength. In the case of distance, it's not just that "it's red", but that the entire spectrum has been shifted in the direction of red. That means the features that correspond to, say, a specific Hydrogen emission, appear slightly offset from where they would if you were looking at it in a lab. When you look at age and size, you're looking at the distribution of the spectrum irrespective of a shift and seeing if it's heavier in the red, blue, or somewhere else. That tells you a lot about composition and mass, which helps with the age and size questions. TL;DR: the use of color terms (e.g., "red") is oversimplifying what astronomers actually do which is an analysis of the overall spectrum and its properties.
  - ggm 4y ago
    Thank you. thats a very helpful clarifying answer.
marze 4y ago
From the abstract: "Using stellar population modelling, we find the galaxies typically contain a hundred million solar masses in stars, in stellar populations that are less than one hundred million years old. The moderate star formation rates and compact sizes suggest elevated star formation rate surface densities, a key indicator of their formation pathways. Taken together, these measurements show that the first galaxies contributing to cosmic reionisation formed rapidly and with intense internal radiation fields."
daxfohl 4y ago
> The sliver of sky observed is about the size of the queen’s eye “on a pound coin held at arm’s length,” So it can be seen by the naked eye? Granted, not at full resolution, but still, I'd have guessed several orders of magnitude smaller.
- dinosaurdynasty 4y ago
  The article doesn't make it obvious but that's not the size of the galaxy, that's the size of the part of the sky they looked through. They make it sound like they looked through 100,000 galaxies in that sliver of sky and found the 2-4 older-than-anything-we've-seen-before galaxies.
- dotnet00 4y ago
  That's just the size, to see it with the naked eye it'd need to be bright enough and in the right wavelength range but it is neither bright enough nor in a wavelength visible to the naked eye.
lovelearning 4y ago
> "we can be absolutely confident of their fantastic distances" My current layperson's understanding is: 1) Redshift-to-distance conversion is a calibration based on the distance ladder. 2) And the distance ladder itself seems to have come under some doubt recently due to the "cosmological crisis" [1]. Can someone here ELI5 how they can be absolutely confident of these distances? [1] "JWST just made the Crisis in Cosmology WORSE" https://www.youtube.com/watch?v=hps-HfpL1vc https://www.youtube.com/watch?v=hps-HfpL1vc
- CrimsonRain 4y ago
  I love astronomy since I was a kid. It is amazing how much we've figured out and still doing so everyday. However, I realized this long ago (in my teens) that much of the stats, eg numbers of stars/planets in the universe, their distances/compositions/ages etc, while calculated, are built on top of multiple instances of approximation/assumption/insufficient data. We know very well how a simple early rounding can lead to widely different end result in a chain of equations. Imagine that in a gigantic situation. In my teen years, I've always wondered why they are not launching Hubble 2.0 3.0 etc every 5 years. Because that's what we need. More state of the art observatories out there in space to gather more data. Without that, we're just increasing the chain of assumptions and approximations.
  - sandworm101 4y ago
    We have. In fact since the 1960s new space telescopes have been launched far more often than every five years, some bigger than hubble. https://en.wikipedia.org/wiki/List_of_space_telescopes https://en.wikipedia.org/wiki/List_of_space_telescopes
- magicalhippo 4y ago
  > Can someone here ELI5 how they can be absolutely confident of these distances? The way I read it is that they're absolutely confident of their fantastic young age, that is, their redshift. As you point out, the age-to-distance conversion isn't quite settled, but that doesn't really matter in this context I think, as younger will still mean further away. So these galaxies will still be the furthest away (for now) even if the distance ladder gets adjusted "inward", ie closer to us.
andrewstuart 4y ago
Could these galaxies have formed earth like planets and potentially life?
- Tepix 4y ago
  I think it is too early to tell, however there may not have been enough stuff other than Hydrogen and Helium in the early universe to get terrestial planets. Very large stars on the other hand don't live very long (just tens of millions of years) before they go Supernova and produce the elements that are heavier than iron.
  - thechao 4y ago
    Hopefully we'll get a drive by: is there a chart showing the relative distribution of elements on, say, a weakly logarithmic scale, overt time? Like: 0 — 98% H, 2% He, 10^6 ..., 10^7 ..., ..., now.
gnz11 4y ago
Well, time to update my username. I suppose I knew this day would come.
- fasteo 4y ago
  For those wondering [1] GN-z11 is a high-redshift galaxy found in the constellation Ursa Major. It is one of the farthest known galaxies from Earth ever discovered [1] https://en.wikipedia.org/wiki/GN-z11 https://en.wikipedia.org/wiki/GN-z11
Tepix 4y ago
It seems a bit underwhelming to go from 400 million years after the big bang to 350 million years. I hope JWST will deliver us even older galaxies in the near future.
- astroH 4y ago
  I think this is perhaps the wrong way to think about it. 50 million years represents ~14% of the age of the Universe (at 350 Myr) so it's really quite a big jump. Considering stars aren't thought to form until 200-250 Myr after the Big Bang, we're talking 33%-50% closer to this period. That's quite remarkable considering the was well out of reach just a year ago.
  - RHSman2 4y ago
    Time is relative ;)
FollowingTheDao 4y ago
Time? Distance? What are all of you talking about? ;)

76 points by cheinyeanlim 4y ago

ggm 4y ago

One of the things which helps with "how far" is time: if you can wait until something has rotated a bit, then you get sideways distance to do triangulation. (because the path of the earth in orbit defines a wider baseline so two observations at the equinoxes (for instance) give you maximal distance. If you can wait even longer you get other rotational movements but some of those "longers" are very long.) As a student in the amateur astronomy space (I didn't progress far) I was quite purturbed by the main sequence "colour == size" thing and the parallel lanes of "colour == distance" and "colour == age" It felt like cheating to put 3 qualities into play, all of which could undermine the others. I'm not even really sure I think you can have two. Maybe there is some unstated principle that all dull things are old and all red dull things are old and far away, but if you also think all old red dull things are huge but all you got was "it's red" then it's feeling shakey. Pick one.

defrost 4y ago
Triangulation doesn't especially add much (or, in fact anything at all) when the base of the triangle is 2 AU across (the diameter of the Earth's orbit, or roughly 16 light minutes) and the long axis of the triangle is 13.4 billion light years.
- ggm 4y ago
  What about for discounting the false positives of objects which may be "closer in the mirror than they appear" ? I would have thought the differential to movement and the accuracy of a 2AU baseline was meaningful there. And occultation, both of which comes from study of other objects of known distance, which are within the limits of resolution for a 2AU baseline. I believe the GAIA mission pushed to 10-6 arcsec. I can't find a more recent limit online, love to know what it is. (copied from https://astronomy.swin.edu.au/cosmos/t/trigonometric+parallax https://astronomy.swin.edu.au/cosmos/t/trigonometric+paralla...)
  - defrost 4y ago
    These are fair points .. but not especially so for objects this distant. Given what you know from your interest already you might like to, say, work out at what distance objects appear to essentially fixed in position when viewed from either end of a 2 AU baseline. Having a background wallpaper of 'fixed' objects that can be occluded helps to inform us about the closer occluding objects .. but triangulation doesn't assist in depth sorting all the distant objects that appear fixed. My comment above assumed (perhaps incorrectly) that you were referring to the title topic and implying that our motion about the sun was enough to determine the distance to these far objects as the JWT moved through a few orbits.
    - ggm 4y ago
      No, I did make that assumption. I didn't realize the limits to VLBI inside our own contextual frame(s) of reference. Getting more AU into things would be nice but I suppose there are other, nicer, cheaper things we can do. And if the main sequence and redshift thing is good enough, then in the end "how far away it is" can remain defined by that, rather than by geometry.
      - canadianfella 4y ago
      - badcppdev 4y ago
        Replying to you and defrost here. I think the solar system moves ~48 AU around the galactic centre every year. And the Milky Way is doing ~117 AU per year. (Using google for calculations) So maybe that combined with space based telescopes helps to make the parallax method more useful over time. Depending on vectors, etc.
googlryas 4y ago
It's not color == distance though, it is color + brightness. Maybe there is some unknown principle at play but you could say that about anything which is not directly measurable, for example how old the earth is. But, it's the best we've got so far, and it does provide seemingly reasonable results that also align with parallax measurements when parallax is within the usable range.
porcoda 4y ago
"Colour" is oversimplifying it a bit. We're usually concerned with the distribution of light received with respect to wavelength. In the case of distance, it's not just that "it's red", but that the entire spectrum has been shifted in the direction of red. That means the features that correspond to, say, a specific Hydrogen emission, appear slightly offset from where they would if you were looking at it in a lab. When you look at age and size, you're looking at the distribution of the spectrum irrespective of a shift and seeing if it's heavier in the red, blue, or somewhere else. That tells you a lot about composition and mass, which helps with the age and size questions. TL;DR: the use of color terms (e.g., "red") is oversimplifying what astronomers actually do which is an analysis of the overall spectrum and its properties.
- ggm 4y ago
  Thank you. thats a very helpful clarifying answer.

marze 4y ago

From the abstract: "Using stellar population modelling, we find the galaxies typically contain a hundred million solar masses in stars, in stellar populations that are less than one hundred million years old. The moderate star formation rates and compact sizes suggest elevated star formation rate surface densities, a key indicator of their formation pathways. Taken together, these measurements show that the first galaxies contributing to cosmic reionisation formed rapidly and with intense internal radiation fields."

daxfohl 4y ago

> The sliver of sky observed is about the size of the queen’s eye “on a pound coin held at arm’s length,” So it can be seen by the naked eye? Granted, not at full resolution, but still, I'd have guessed several orders of magnitude smaller.

dinosaurdynasty 4y ago
The article doesn't make it obvious but that's not the size of the galaxy, that's the size of the part of the sky they looked through. They make it sound like they looked through 100,000 galaxies in that sliver of sky and found the 2-4 older-than-anything-we've-seen-before galaxies.
dotnet00 4y ago
That's just the size, to see it with the naked eye it'd need to be bright enough and in the right wavelength range but it is neither bright enough nor in a wavelength visible to the naked eye.

lovelearning 4y ago

> "we can be absolutely confident of their fantastic distances" My current layperson's understanding is: 1) Redshift-to-distance conversion is a calibration based on the distance ladder. 2) And the distance ladder itself seems to have come under some doubt recently due to the "cosmological crisis" [1]. Can someone here ELI5 how they can be absolutely confident of these distances? [1] "JWST just made the Crisis in Cosmology WORSE" https://www.youtube.com/watch?v=hps-HfpL1vc https://www.youtube.com/watch?v=hps-HfpL1vc

CrimsonRain 4y ago
I love astronomy since I was a kid. It is amazing how much we've figured out and still doing so everyday. However, I realized this long ago (in my teens) that much of the stats, eg numbers of stars/planets in the universe, their distances/compositions/ages etc, while calculated, are built on top of multiple instances of approximation/assumption/insufficient data. We know very well how a simple early rounding can lead to widely different end result in a chain of equations. Imagine that in a gigantic situation. In my teen years, I've always wondered why they are not launching Hubble 2.0 3.0 etc every 5 years. Because that's what we need. More state of the art observatories out there in space to gather more data. Without that, we're just increasing the chain of assumptions and approximations.
- sandworm101 4y ago
  We have. In fact since the 1960s new space telescopes have been launched far more often than every five years, some bigger than hubble. https://en.wikipedia.org/wiki/List_of_space_telescopes https://en.wikipedia.org/wiki/List_of_space_telescopes
magicalhippo 4y ago
> Can someone here ELI5 how they can be absolutely confident of these distances? The way I read it is that they're absolutely confident of their fantastic young age, that is, their redshift. As you point out, the age-to-distance conversion isn't quite settled, but that doesn't really matter in this context I think, as younger will still mean further away. So these galaxies will still be the furthest away (for now) even if the distance ladder gets adjusted "inward", ie closer to us.

andrewstuart 4y ago

Could these galaxies have formed earth like planets and potentially life?

Tepix 4y ago
I think it is too early to tell, however there may not have been enough stuff other than Hydrogen and Helium in the early universe to get terrestial planets. Very large stars on the other hand don't live very long (just tens of millions of years) before they go Supernova and produce the elements that are heavier than iron.
- thechao 4y ago
  Hopefully we'll get a drive by: is there a chart showing the relative distribution of elements on, say, a weakly logarithmic scale, overt time? Like: 0 — 98% H, 2% He, 10^6 ..., 10^7 ..., ..., now.

gnz11 4y ago

Well, time to update my username. I suppose I knew this day would come.

fasteo 4y ago
For those wondering [1] GN-z11 is a high-redshift galaxy found in the constellation Ursa Major. It is one of the farthest known galaxies from Earth ever discovered [1] https://en.wikipedia.org/wiki/GN-z11 https://en.wikipedia.org/wiki/GN-z11

Tepix 4y ago

It seems a bit underwhelming to go from 400 million years after the big bang to 350 million years. I hope JWST will deliver us even older galaxies in the near future.

astroH 4y ago
I think this is perhaps the wrong way to think about it. 50 million years represents ~14% of the age of the Universe (at 350 Myr) so it's really quite a big jump. Considering stars aren't thought to form until 200-250 Myr after the Big Bang, we're talking 33%-50% closer to this period. That's quite remarkable considering the was well out of reach just a year ago.
- RHSman2 4y ago
  Time is relative ;)

FollowingTheDao 4y ago

Time? Distance? What are all of you talking about? ;)