<p>As I understand it, maps of the sky and three-dimensional maps of the universe all show the <em>observed</em> positions of celestial objects.</p>
<p>Are there any maps that show our best guess at their <em>current</em> positions? Does such a thing have a name? Is it even possible?</p>

CC BY-SA 4.0
2023-08-06T14:36:51.510Z
Someone may be able to make a guesswork map of the universe based on current observations, and extrapolating star positions on their trajectories to the present time.  But it is not possible to make an actual map of the positions of things because there is no such thing as universal simultaneity. Now on earth is not Now on a distant star.
scm
CC BY-SA 4.0
2023-07-27T08:27:40.283Z
are you thinking more about the positions of stars in the galaxy, or galaxies in the universe?  If the latter there is a problem since you're dealing with an expanding spacetime, which makes the whole notion of "position" and "current" harder to conceptualize.
James K
CC BY-SA 4.0
2023-07-27T17:47:13.190Z
Agreed! I know it's difficult or impossible... I'm just trying to get a grasp on what the terminology would be for it, and if anyone has even tried. As it is I don't even know how to google it.
John Wu
CC BY-SA 4.0
2023-07-27T20:43:34.487Z
You could start by helping us by answering the question in my comment.  Are you asking about the positions of stars, which are basically local to us (on a cosmological scale) or distant galaxies (which are remote from us.  The answer are rather different.  1 is possible (but it would look almost exactly how the same as the observed positions)  2 is probably not possible (because notions of "moving" or "now" need to considered in terms of relativity, and become rather harder to define.
James K
CC BY-SA 4.0
2023-07-28T03:19:43.987Z
Terminology-wise, and for Solar System objects, what you want are *geometric* positions, as opposed to *astrometric* positions (which correct for light-time) or to *apparent* positions (which also correct for stellar aberration). JPL Horizons does provide all of them (in the settings), and SkySafari does as well.
Pierre Paquette
CC BY-SA 4.0
2023-07-28T06:34:59.503Z
@JamesK Allow me to me more explicit in n my answer. I am asking for a term that could be used to describe either map. E.g. "It is more difficult to draw an X that encompasses intergalactic distances." What word or phrase would I use instead of X?
John Wu
CC BY-SA 4.0
2023-07-28T07:23:26.947Z
I don't think such maps are drawn, and so there is no term for it
James K
CC BY-SA 4.0
2023-07-31T13:26:12.240Z
Any planetarium software will do this.  For nearby objects like the solar system, it's quite important.  For more distant objects like stars, less so, but still doable and the phrase to describe it is called "proper motion".  For even more distant objects like galaxies, motions can be computed, but their motion over human timescales would be too small to be plotted on a map.
Greg Miller
<astrophysics><cosmology><star-maps><time-domain-astronomy>
Is there such a thing as a map that shows the current (not observed) positions of celestial objects?
John Wu
# Is there such a thing as a map that shows the current (not observed) positions of celestial objects?

(Asked by: username_0 on 2023-07-27)

As I understand it, maps of the sky and three-dimensional maps of the universe all show the *observed* positions of celestial objects.

Are there any maps that show our best guess at their *current* positions? Does such a thing have a name? Is it even possible?

**Tags:** astrophysics, cosmology, star-maps, time-domain-astronomy

> **Comments:**
> **username_2**: are you thinking more about the positions of stars in the galaxy, or galaxies in the universe?  If the latter there is a problem since you're dealing with an expanding spacetime, which makes the whole notion of "position" and "current" harder to conceptualize.  
> **username_0**: Agreed! I know it's difficult or impossible... I'm just trying to get a grasp on what the terminology would be for it, and if anyone has even tried. As it is I don't even know how to google it.  
> **username_2**: You could start by helping us by answering the question in my comment.  Are you asking about the positions of stars, which are basically local to us (on a cosmological scale) or distant galaxies (which are remote from us.  The answer are rather different.  1 is possible (but it would look almost exactly how the same as the observed positions)  2 is probably not possible (because notions of "moving" or "now" need to considered in terms of relativity, and become rather harder to define.  
> **username_3**: Terminology-wise, and for Solar System objects, what you want are *geometric* positions, as opposed to *astrometric* positions (which correct for light-time) or to *apparent* positions (which also correct for stellar aberration). JPL Horizons does provide all of them (in the settings), and SkySafari does as well.  
> **username_0**: @JamesK Allow me to me more explicit in n my answer. I am asking for a term that could be used to describe either map. E.g. "It is more difficult to draw an X that encompasses intergalactic distances." What word or phrase would I use instead of X?  
> **username_2**: I don't think such maps are drawn, and so there is no term for it  
> **username_4**: Any planetarium software will do this.  For nearby objects like the solar system, it's quite important.  For more distant objects like stars, less so, but still doable and the phrase to describe it is called "proper motion".  For even more distant objects like galaxies, motions can be computed, but their motion over human timescales would be too small to be plotted on a map.  
> **username_1**: Someone may be able to make a guesswork map of the universe based on current observations, and extrapolating star positions on their trajectories to the present time.  But it is not possible to make an actual map of the positions of things because there is no such thing as universal simultaneity. Now on earth is not Now on a distant star.  

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