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Stars or Galaxies


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Good afternoon from the USA.

 

When one looks up at the night sky and sees all those pinpoints if lights, are they most likely stars or galaxies?

I'm a little confused since I've googled this topic recently and they all seem to run 50-50. 

Is the answer 50-50 or is there a more precise answer?

Before I joined this forum I always thought most of those dots of lights were galaxies because that's what I read years ago.

Correct me if I'm wrong.

Thanks. 

Lost In Space.

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Hi when you look up you are seeing stars, the Galaxies are out there but you can't see them with the naked eye , apart from M31 Andromeda, in the northern hemisphere. Hope this helps.The stars you see are within our own milky way galaxy.

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And all of those stars that you can see are strictly within the Milky Way galaxy, our home galaxy.

On top of that, only about 3000 to 5000 of the billions of stars in the MW are visible to the naked eye, and most of them are relatively near to us.

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10 hours ago, Spile said:

I remember seeing a galactic map that not only displayed the sun but also the naked eye visible stars. Does anyone have a link?

You can generate one on most computer planetarium packages simply by limiting the magnitudes it presents to whatever is your naked eye limit, so 5.5 to 6.0 for most people, I guess.

Olly

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On 28/05/2023 at 17:47, Goldfinger said:

When one looks up at the night sky and sees all those pinpoints if lights, are they most likely stars or galaxies?

I'm a little confused since I've googled this topic recently and they all seem to run 50-50. 

As already mentioned above they are all going to be stars from our own galaxy. Galaxies will appear as fuzzy blobs even in telescopes when viewed visually. With cameras you are likely to see more detail. Think about it this way, our nearest galaxy is around 70,000 light years away. Our very own galaxy has a radius of approx 50k ly and we cant even see all the stars which are possibly there on the outer periphery. So the only time we can really observe a star from another galaxy is when there is an event like a supernova (eg the one thats visible in M101 at the moment)

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28 minutes ago, vlaiv said:

This brings on an interesting topic - how many galaxies can be actually seen with a naked eye?

M31, M33, LMC, SMC are those that I can think of, but apparently - there is more:

https://en.wikipedia.org/wiki/List_of_galaxies#Naked-eye_galaxies

 

I can never see M33 though I find M31 dead easy.

Olly

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2 minutes ago, ollypenrice said:

I can never see M33 though I find M31 dead easy.

Olly

I knew it was possible from Bortle scale definition:

Quote

M33 (the Triangulum Galaxy) is a direct vision naked-eye object

That is for Bortle 1 sky. It is supposed to be averted vision target in Bortle 3 skies and even Bortle 4 (when high in the sky).

https://en.wikipedia.org/wiki/Bortle_scale

but never saw it myself without a pair of binoculars or a telescope. I managed once to get a glimpse from Bortle 7 with pair of 35mm bins - but I lost it and could not find it again that night.

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13 hours ago, ollypenrice said:

You can generate one on most computer planetarium packages simply by limiting the magnitudes it presents to whatever is your naked eye limit, so 5.5 to 6.0 for most people, I guess.

Olly

I am thinking of the perspective of outside our galaxy rather than from earth.

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48 minutes ago, Spile said:

I am thinking of the perspective of outside our galaxy rather than from earth.

I'm not sure that you'll be able to see the sun and visible stars from the outside of our galaxy.

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16 hours ago, vlaiv said:

This brings on an interesting topic - how many galaxies can be actually seen with a naked eye?

We could include our own as we can see the core 🙂 And we can see a few nebulae too eg M42

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I have actually seen M33, one early winter night when I had got up to shut down the imaging. A faint but definite fuzzy blob. I wondered what it was, only realised that it was M33 after looking on Stellarium. It was quite a spectacular night with Auriga glittering with clusters. LP map says 21.7

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22 hours ago, vlaiv said:

I'm not sure that you'll be able to see the sun and visible stars from the outside of our galaxy.

Doesn’t that depend on how far out you are?

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59 minutes ago, Larry B36 said:

If you are outside our galaxy and at the same time close enough to its edge, then it is theoretically possible to see the Sun. However, it is worth remembering that there are many obstacles inside the galaxy that can limit the visibility of even nearby stars.

Not really sure about that.

Depends in which direction outside of the galaxy we are talking about, but I doubt it even for the shortest path.

Sun has apparent magnitude of 4.83 at 10 parsecs. For the sake of argument - let's say that NELM from outside of the galaxy is ~9, so the difference between the two is ~5 magnitudes.

This allows for only x100 difference in intensity. Now, intensity drops with square of distance, so this is really only sqrt(100) = x10 of distance. In another words, Sun will be seen as mag9 star from 10 x 10 parsecs away. That is 100pc or 326 light years.

Now some info on Milky Way - thickness of the thin disk is only 220–450 pc (718–1,470 ly). It looks like Sun is situated smack in the middle of it (here is scheme from Wiki):

458px-Milky_way_profile.svg.png

So there is at least 110pc to the edge of thin disk - and we could argue that outside of the galaxy is at least outside of thick disk, let alone galactic halo.

Given the above - I doubt that Sun is visible from outside of our galaxy.

 

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1 hour ago, Mr Spock said:

I've seen M33 from a dark sky site. I used to be able to see M31 from here until those pesky LED streetlights appeared a few years ago 😡

I can just make out m31 with averted vision on a good night from here.  Wonder what it was like before the LEDs.

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On 29/05/2023 at 14:58, Louis D said:

And all of those stars that you can see are strictly within the Milky Way galaxy, our home galaxy.

On top of that, only about 3000 to 5000 of the billions of stars in the MW are visible to the naked eye, and most of them are relatively near to us.

About 5000 visible to us , but the Earth gets in the way of a lot of them so we can never actually see more than about 2000 ... 😏

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1 hour ago, Steve Ward said:

About 5000 visible to us , but the Earth gets in the way of a lot of them so we can never actually see more than about 2000 ... 😏

Definitely.  As I wrote that, I was thinking about how many stars will never be seen throughout the year from any given point on the Earth's surface.  You would need to travel to the opposite hemisphere and observe for a year there to catch all of the stars visible from both the northern and southern hemispheres.  I think that's why the number I looked up was so vague.  Even at the equator you would have trouble observing stars at or near the poles.

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