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I couldn't believe that first image. You could clearly see the gravitational lensing causing the light to form arcs. Even for someone who knows nothing about a

I couldn't believe that first image. You could clearly see the gravitational lensing causing the light to form arcs. Even for someone who knows nothing about astronomy it was super exciting.

ycombinete 4y ago
Apparently some of those discs were the same galaxy see in multiple places due to the power of the lensing?
- thamer 4y ago
  Yes, and they confirmed it was the same galaxy using spectroscopy: https://webbtelescope.org/contents/media/images/2022/035/01G7HRMY93K0BCCBKCABAQH0V7 https://webbtelescope.org/contents/media/images/2022/035/01G...
  - londons_explore 4y ago
    Presumably the path lengths are probably not identical... That means we might be able to see the same galaxy twice at different points in time? That should be a really good way to check our models are accurate!
    - leeoniya 4y ago
      i read somewhere recently that this difference in path lengths can be measured in days, depending on distance and how off-center the lensing is.
      - lasc4r 4y ago
        That's pretty amazing, I'd certainly not expect more than a small time shift since it still managing to get the same light source to the same location to be detected.
        btilly 4y ago
        The lensed light has generally traveled for billions of years, and wound up being separated by thousands of light years before the gravitational lensing. Two paths taking days apart DOES count as only a small time shift!
        leeoniya 4y ago
        or decades https://news.berkeley.edu/2015/03/05/distant-supernova-split-four-ways-by-gravitational-lens/ https://news.berkeley.edu/2015/03/05/distant-supernova-split...
    - victor9000 4y ago
      Interesting, it should be theoretically possible to use gravitational lensing to view a past version of earth, no?
      - beckingz 4y ago
        You would probably need a telescope larger than earth to do this.
        Spare_account 4y ago
        Using interferometery of orbiting observatories (potentially on solar orbits, to leverage the entire diameter of the solar system), this is conceivably possible
        tomjakubowski 4y ago
        Having just visited Mt. Wilson, and learning about CHARA, this idea sounds fantastic.
      - mortehu 4y ago
        Is there anything we can do deliberately to use gravitational lensing other than aiming a telescope at a part of the sky where this is happening by random chance?
        lasc4r 4y ago
        Other than deliberately pointing a telescope at massive objects, I'd say no.
        ckw 4y ago
        Video discussing the use of the sun as a gravitational lens to image exoplanets: https://youtu.be/NQFqDKRAROI https://youtu.be/NQFqDKRAROI
      - holoduke 4y ago
        Would there be fotons of walking dinosaur still floating around into our direction after making a complete u turn somewhere?
    - jagraff 4y ago
      This has actually been done before - scientists have been able to image the same supernova multiple times from a gravitationally lensed galaxy: https://www.universetoday.com/151581/astronomers-saw-the-same-supernova-three-times-thanks-to-gravitational-lensing-and-in-twenty-years-they-think-theyll-see-it-one-more-time/ https://www.universetoday.com/151581/astronomers-saw-the-sam...
      - seanw444 4y ago
        Now that is fascinating.
    - antognini 4y ago
      These kinds of observations have frequently been made for lensed quasars. Quasars are fairly stochastic and have random bursts in their brightness. If you see multiple images of the same quasar, you can see one of the images get brighter and then some time later (usually of order days) you can see the other image get brighter. By measuring the time delay and the separations between the images you can get an estimate of the Hubble constant.
- superposeur 4y ago
  I seem to remember an astronomer mentioning that it is possible to interfere the light from gravitationally lensed double images. Lacking appropriate intuition, this would be amazing for me as I’d think the photons would lose coherence over the course of their multi billion light year journeys (but maybe not?). Does anyone know about this?
  - HPsquared 4y ago
    Interferometry is common in radio telescopes, and was the method used in the recent imaging of a black hole by the Event Horizon Telescope, which used interferometry between multiple telescopes on different sides of the earth. It's also used a bit in optical telescopes, but harder to do. Basically yes, interference can still be used even over these extreme distances. The speed of light is pretty exact I suppose! https://en.m.wikipedia.org/wiki/Event_Horizon_Telescope https://en.m.wikipedia.org/wiki/Event_Horizon_Telescope https://en.m.wikipedia.org/wiki/Astronomical_interferometer https://en.m.wikipedia.org/wiki/Astronomical_interferometer
    - superposeur 4y ago
      Interesting, thanks for the links. Looking at them, though, it would appear that the two "paths" being interfered differ in length on the order of the separation between the two telescopes -- i.e. meters or kilometers -- rather than astronomical distances. Using the speed of light, this corresponds to a difference in flight time of the light on the order of nanoseconds or seconds. I can imagine how the light traversing the two paths could remain unmolested by stray random, environmental phase shifts during such short times (necessary if you want them to interfere). On the other hand, the double images in the photo would have a difference in flight times of years? But, again, I don't really understand precisely what the astronomer was referring to, or have proper intuition for the conditions of space through which astronomical photons travel...
  - api 4y ago
    Photons travel at c, so don’t they experience no time? Wouldn’t they be zero old?
TedShiller 4y ago
I'm not sure that assessment is accurate
- jacobedawson 4y ago
  "The telescope’s first public image shows a cluster of galaxies called SMACS 0723, which is so heavy it warps and magnifies the light from distant galaxies beyond it."
  - TedShiller 4y ago
    This is accurate. However, it wouldn't be just based on the assessment of someone who knows nothing about astronomy.
    - seanhunter 4y ago
      I said it was exciting for me as someone who didn’t know about astronomy. I’m very amply qualified to make that assessment. Gravitational lensing and how it shows in images is something I learned about by attending a lecture.
- falseprofit 4y ago
  What part?
whekdhek 4y ago
It's a nice image, but it's not the first time we've seen something like that pretty clearly. https://news.uchicago.edu/story/gravitational-lens-reveals-details-distant-ancient-galaxy https://news.uchicago.edu/story/gravitational-lens-reveals-d...
- jffry 4y ago
  It's not even the first time this little bit of the sky has been imaged by one of our space telescopes, but that makes the image no less beautiful. It's really cool to see all the additional, older galaxies visible in JWST's infrared which were not previously visible to Hubble!
- drexlspivey 4y ago
  Gravitational lensing was how general relativity was "proven" back in 1919 [1] (4 years after publication). Einstein had predicted this weird effect but it was impossible to see in action because the only observable object massive enough to cause lensing was the sun and you cannot take a picture of it. In 1919 they managed to take a picture of the sun during a total sun eclipse which showed the effect clearly. [1] https://www.discovermagazine.com/the-sciences/how-the-1919-solar-eclipse-made-einstein-the-worlds-most-famous-scientist https://www.discovermagazine.com/the-sciences/how-the-1919-s...
867-5309 4y ago
I wonder if it's additive/accumulative i.e. every star in the galaxy lends itself to the effect, or if it comes mainly from the SMBH at the centre of the galaxy, or a combination of both?
- throwaway64643 4y ago
  I guess it's mostly from dark matter.
  - lutorm 4y ago
    Well, it's from the total mass, but yeah that's mostly dark matter.
mrtweetyhack 4y ago

I couldn't believe that first image. You could clearly see the gravitational lensing causing the light to form arcs. Even for someone who knows nothing about astronomy it was super exciting.

ycombinete 4y ago

Apparently some of those discs were the same galaxy see in multiple places due to the power of the lensing?

thamer 4y ago
Yes, and they confirmed it was the same galaxy using spectroscopy: https://webbtelescope.org/contents/media/images/2022/035/01G7HRMY93K0BCCBKCABAQH0V7 https://webbtelescope.org/contents/media/images/2022/035/01G...
- londons_explore 4y ago
  Presumably the path lengths are probably not identical... That means we might be able to see the same galaxy twice at different points in time? That should be a really good way to check our models are accurate!
  - leeoniya 4y ago
    i read somewhere recently that this difference in path lengths can be measured in days, depending on distance and how off-center the lensing is.
    - lasc4r 4y ago
      That's pretty amazing, I'd certainly not expect more than a small time shift since it still managing to get the same light source to the same location to be detected.
      - btilly 4y ago
        The lensed light has generally traveled for billions of years, and wound up being separated by thousands of light years before the gravitational lensing. Two paths taking days apart DOES count as only a small time shift!
      - leeoniya 4y ago
        or decades https://news.berkeley.edu/2015/03/05/distant-supernova-split-four-ways-by-gravitational-lens/ https://news.berkeley.edu/2015/03/05/distant-supernova-split...
  - victor9000 4y ago
    Interesting, it should be theoretically possible to use gravitational lensing to view a past version of earth, no?
    - beckingz 4y ago
      You would probably need a telescope larger than earth to do this.
      - Spare_account 4y ago
        Using interferometery of orbiting observatories (potentially on solar orbits, to leverage the entire diameter of the solar system), this is conceivably possible
        tomjakubowski 4y ago
        Having just visited Mt. Wilson, and learning about CHARA, this idea sounds fantastic.
    - mortehu 4y ago
      Is there anything we can do deliberately to use gravitational lensing other than aiming a telescope at a part of the sky where this is happening by random chance?
      - lasc4r 4y ago
        Other than deliberately pointing a telescope at massive objects, I'd say no.
      - ckw 4y ago
        Video discussing the use of the sun as a gravitational lens to image exoplanets: https://youtu.be/NQFqDKRAROI https://youtu.be/NQFqDKRAROI
    - holoduke 4y ago
      Would there be fotons of walking dinosaur still floating around into our direction after making a complete u turn somewhere?
  - jagraff 4y ago
    This has actually been done before - scientists have been able to image the same supernova multiple times from a gravitationally lensed galaxy: https://www.universetoday.com/151581/astronomers-saw-the-same-supernova-three-times-thanks-to-gravitational-lensing-and-in-twenty-years-they-think-theyll-see-it-one-more-time/ https://www.universetoday.com/151581/astronomers-saw-the-sam...
    - seanw444 4y ago
      Now that is fascinating.
  - antognini 4y ago
    These kinds of observations have frequently been made for lensed quasars. Quasars are fairly stochastic and have random bursts in their brightness. If you see multiple images of the same quasar, you can see one of the images get brighter and then some time later (usually of order days) you can see the other image get brighter. By measuring the time delay and the separations between the images you can get an estimate of the Hubble constant.
superposeur 4y ago
I seem to remember an astronomer mentioning that it is possible to interfere the light from gravitationally lensed double images. Lacking appropriate intuition, this would be amazing for me as I’d think the photons would lose coherence over the course of their multi billion light year journeys (but maybe not?). Does anyone know about this?
- HPsquared 4y ago
  Interferometry is common in radio telescopes, and was the method used in the recent imaging of a black hole by the Event Horizon Telescope, which used interferometry between multiple telescopes on different sides of the earth. It's also used a bit in optical telescopes, but harder to do. Basically yes, interference can still be used even over these extreme distances. The speed of light is pretty exact I suppose! https://en.m.wikipedia.org/wiki/Event_Horizon_Telescope https://en.m.wikipedia.org/wiki/Event_Horizon_Telescope https://en.m.wikipedia.org/wiki/Astronomical_interferometer https://en.m.wikipedia.org/wiki/Astronomical_interferometer
  - superposeur 4y ago
    Interesting, thanks for the links. Looking at them, though, it would appear that the two "paths" being interfered differ in length on the order of the separation between the two telescopes -- i.e. meters or kilometers -- rather than astronomical distances. Using the speed of light, this corresponds to a difference in flight time of the light on the order of nanoseconds or seconds. I can imagine how the light traversing the two paths could remain unmolested by stray random, environmental phase shifts during such short times (necessary if you want them to interfere). On the other hand, the double images in the photo would have a difference in flight times of years? But, again, I don't really understand precisely what the astronomer was referring to, or have proper intuition for the conditions of space through which astronomical photons travel...
- api 4y ago
  Photons travel at c, so don’t they experience no time? Wouldn’t they be zero old?

TedShiller 4y ago

I'm not sure that assessment is accurate

jacobedawson 4y ago
"The telescope’s first public image shows a cluster of galaxies called SMACS 0723, which is so heavy it warps and magnifies the light from distant galaxies beyond it."
- TedShiller 4y ago
  This is accurate. However, it wouldn't be just based on the assessment of someone who knows nothing about astronomy.
  - seanhunter 4y ago
    I said it was exciting for me as someone who didn’t know about astronomy. I’m very amply qualified to make that assessment. Gravitational lensing and how it shows in images is something I learned about by attending a lecture.
falseprofit 4y ago
What part?

whekdhek 4y ago

It's a nice image, but it's not the first time we've seen something like that pretty clearly. https://news.uchicago.edu/story/gravitational-lens-reveals-details-distant-ancient-galaxy https://news.uchicago.edu/story/gravitational-lens-reveals-d...

jffry 4y ago
It's not even the first time this little bit of the sky has been imaged by one of our space telescopes, but that makes the image no less beautiful. It's really cool to see all the additional, older galaxies visible in JWST's infrared which were not previously visible to Hubble!
drexlspivey 4y ago
Gravitational lensing was how general relativity was "proven" back in 1919 [1] (4 years after publication). Einstein had predicted this weird effect but it was impossible to see in action because the only observable object massive enough to cause lensing was the sun and you cannot take a picture of it. In 1919 they managed to take a picture of the sun during a total sun eclipse which showed the effect clearly. [1] https://www.discovermagazine.com/the-sciences/how-the-1919-solar-eclipse-made-einstein-the-worlds-most-famous-scientist https://www.discovermagazine.com/the-sciences/how-the-1919-s...

867-5309 4y ago

I wonder if it's additive/accumulative i.e. every star in the galaxy lends itself to the effect, or if it comes mainly from the SMBH at the centre of the galaxy, or a combination of both?

throwaway64643 4y ago
I guess it's mostly from dark matter.
- lutorm 4y ago
  Well, it's from the total mass, but yeah that's mostly dark matter.

mrtweetyhack 4y ago