Do new objects ever become visible to us for the first time?

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Discussion Overview

The discussion revolves around whether new astronomical objects can become visible to us for the first time due to the universe's age and expansion. Participants explore the implications of observing distant objects and the nature of their visibility over time, touching on theoretical and observational aspects.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • Some participants propose that light from distant objects continues to reach us, suggesting that new visibility could occur, though they question if this will happen again given the universe's age and expansion.
  • Others argue that as we observe further away, we are looking into the past and can see the evolution of existing objects, such as stars and galaxies, rather than new formations appearing suddenly.
  • A participant uses an analogy of a forest to illustrate that new stages in the evolution of objects are visible over time, with examples like the ignition of protostars and supernovae representing rapid changes.
  • Another participant affirms that fully formed structures like galaxies do not suddenly appear; instead, light from precursor structures reaches us before the light from mature galaxies does.

Areas of Agreement / Disagreement

Participants generally agree that fully formed astronomical structures do not suddenly become visible, but there is some debate about the implications of observing new stages of evolution and whether new visibility will occur in the future.

Contextual Notes

The discussion includes assumptions about the nature of light travel and the evolution of astronomical objects, which may depend on specific definitions of visibility and formation. There are also unresolved questions regarding the conditions under which new visibility might occur.

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Does light from distant objects still continue to reach us "for the first time," or is the universe sufficiently old and its expansion sufficiently fast that this will never again happen? If it does happen, do we have any examples of it? Also, if so, what does it "look like" (i.e. does something just magically seem to all of the sudden appear)?
 
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As you look further away, you are looking into the past.
The analogy here is being in a forest where the trees get younger and younger towards the edges - over time you see the distant trees grow taller and get older, in the far distance sprouts put forth leaves and grow to saplings, and, in the clear ground outside the forest, new sprouts poke their heads up.

Thus: we get to see new stages in the evolution of the objects that are already there.
Sometimes this is a slow process, like the accretion of a cloud of dust into a star.
The ignition of the protostar could be quite quick, particularly in visible light, so that would be the "sudden appearance of a new object" if you like. Similarly a supernova is a very quick event.

So what it looks like is just the same as the normal changes around us every day.
What you won't see is fully formed stars or galaxies just popping into visibility - they have to grow into being, like the trees.
 
I was about to ask if we see new "formations" then, but that leaves the question already answered (thinking about the Hubble deep images of "baby" galaxies, and consequently "baby" things within them), gradually of course. Thanks
 
To affirm what Simon already said, fully formed structures, like galaxies, never suddenly pop into view. This is the inference often drawn from talk of there being galaxies in the universe whose light has not yet had time to reach us. What they fail to mention is light emanated by their precursor structures will reach us long before that of the mature galaxy.
 

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