Apart from stars and galaxies, what are the most distant extended objects that we have ever seen? For example, can gas clouds or nebulae be seen in other galaxies?

In the list referred to in the link only farawy galaxies are mentioned. Images of the closest galaxy, Andromeda, show separate stars. Can nebulae be observed it? Or other non-starry objects? Stars will obviously stay point-like. I'm asking if the extended objects (much bigger than stars) be seen, with the help of time exposed photographs maybe?

By an extended object I don't mean stars or groups of stars. These are easily seen. I mean things like nebulae or other large scale structures. Can these even be observed in other galaxies?

  • $\begingroup$ en.wikipedia.org/wiki/… $\endgroup$ Jun 26 at 2:26
  • $\begingroup$ @NilayGhosh Thanks for the link. Unfortunately there are only atars and galaxies and artist impressions. $\endgroup$ Jun 26 at 2:34
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    $\begingroup$ @DescheleSchilder This is an interesting question! I think it will help if you clarify a little bit. If you'd like to ask about farthest resolved galaxy that's one question, the farthest galaxies observed are much farther and unresolved, do you want to exclude them by using "extended" to mean "resolved"? Of course a barely resolved galaxy will be a lot farther than "a nebula seen inside another galaxy". Those would have to be a lot closer. just fyi most of those images are from various telescopes, only a few are artists impressions. $\endgroup$
    – uhoh
    Jun 26 at 6:26
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    $\begingroup$ @DescheleSchilder Although it's hard to notice this, there are at least a couple of non-stellar, extended sources in the Wiki list Nilay Ghosh pointed to -- e.g., the cluster CL J1001+0220 and the "PJ352–15 quasar jet". $\endgroup$ Jun 26 at 14:29
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    $\begingroup$ @DescheleSchilder I get the impression it can maybe be seen in X-rays, but definitely in the radio with very-long-baseline interferometry (e.g., iopscience.iop.org/article/10.3847/1538-4357/aac76f -- "The VLBA observations presented here resolve this quasar into multiple components with an overall linear extent of 1.62 kpc"). $\endgroup$ Jun 26 at 15:39

The Universe itself is an extended object. The earliest image of the Universe that we are able to currently obtain is the cosmic microwave background (CMB) radiation, which is more technically known as the surface of last scattering since it is when photons from the early Universe were able to decouple from the dense plasma. This occurred when the Universe was about 300,000 years old, so it's like a baby picture of the Universe. This object is more distant than any galaxy or star or other astronomical object.

Perhaps you don't like that answer, well okay. The first galaxies and stars (population III stars) have not yet been observed conclusively, but future observatories may lead the way to this. Depending on how cosmological structure formed (used to be thought to be monolithic, but nowadays we think in terms of hierarchical formation), these early galaxies could have formed before cosmic filaments. It is an open question about when the first dark matter formed, whether before or after or concurrently with these early galaxies.

The galaxy that we have observed to be furthest away, so far, is called GN-z11, which is calculated to have formed around 400 million years after the big bang.

Astrophysical jets can be seen directly and in some cases are well resolved. Sometimes they are produced by the nucleus of other galaxies, like M87, or are produced by very strong magnetic field environments, like pulsars. An example of the latter is pulsar IGR J11014-6103, also called the Lighthouse nebula. This pulsar has the largest jet so far observed in the Milky Way, and whose velocity is estimated at 0.8 times the speed of light in vacuum. From the wiki: "The jet, aligned with the pulsar rotation axis, is perpendicular to the pulsar's trajectory and extends out over 37 light-years (about nine times the distance from our sun to the nearest visible star)." The image below depicts this pulsar's jet.

For some more examples of resolved astrophysical jets, see here.

enter image description here


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