Are the stars that we see in constellations within the Milky Way galaxy?

[FactChecker]

Are the stars that we see in constellations within the Milky Way galaxy? Should I assume that they are close and within the Milky Way?

 

[Ibix]

Yes, as far as I'm aware. There are naked-eye visible extra-galactic objects (the Magellanic clouds, Andromeda galaxy), but individual stars are too dim.

 

[snorkack]

Yes, as far as I'm aware. There are naked-eye visible extra-galactic objects (the Magellanic clouds, Andromeda galaxy), but individual stars are too dim.

Great majority of time. The brightest long term stars in Magellanic clouds are around magnitude +9, which is too dim to see. SN1987A was an easy naked eye object at +2,7, and it is a star, but these are not frequent.

 

[phinds]

Are the stars that we see in constellations within the Milky Way galaxy? Should I assume that they are close and within the Milky Way?

Yes. You actually CAN see galaxies (well, Andromeda, at least) outside of the milky way (with the naked eye) but not individual stars.

 

[FactChecker]

Yes. You actually CAN see galaxies (well, Andromeda, at least) outside of the milky way (with the naked eye) but not individual stars.

Thanks all. It sounds like it is a question of identifying the individual points of a constellation to determine if they are stars or galaxies. The stars will be within the Milky Way.

 

[DaveC426913]

It would be an interesting exercise to determine the farthest star that is part of a constellation. I am certain they'd all be from our spiral arm.

Update:
The farthest naked eye visible star is 4000 light years distant.

https://www.kqed.org/quest/236/the-...nt individual star,more luminous than our Sun.

 

[snorkack]

Thanks all. It sounds like it is a question of identifying the individual points of a constellation to determine if they are stars or galaxies. The stars will be within the Milky Way.

There are more options.
Omega Centauri is a naked eye object and a lettered part of the constellation. But it is neither a star nor a galaxy. It is perceptibly extended... for telescope. Ptolemy catalogues it as a star (on centaur´s back), it took Halley´s telescope to spot its nebulosity. It actually is a star cluster, in Milky Way. There are other clusters designated with star letters, such as Chi and h Persei (also in Milky Way). And more clusters under star numbers, such as 47 Tucanae (in Milky Way) and 30 Doradus (not in Milky Way).
But these do not seem to form parts of constellation figures. Andromeda herself is in northern sky and has a story, but her Nebula notoriously does not... Ptolemy makes no mention of nebula, only mentioned in 10th century Arab sources. And Doradus, Mensa and Tucana are southern sky. How far do the pictures of Goldfish and Toucan rely on the nebulosity of the Clouds, besides the stars in the foreground in Milky Way?

 

[George Jones]

Thanks all. It sounds like it is a question of identifying the individual points of a constellation to determine if they are stars or galaxies. The stars will be within the Milky Way.

There are no galaxies that are included in the connect-the-points outlines of constellations. There may be others, but the only non-stellar object of which I can think that is included in a connect-the-points outline is the star-forming region M42 (Great Nebula; in our neck of the woods), which is part of Orion's sword.

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

 

[collinsmark]

Are the stars that we see in constellations within the Milky Way galaxy? Should I assume that they are close and within the Milky Way?

Short answers: Yes and yes.

If, with the naked eye, you're looking at something [bright] in the night sky, and it looks like a "star" (i.e., a pinpoint of light), you can bet it's in the Milky Way galaxy and it's relatively close. While thousands of light-years away is possible, hundreds is more likely. Less than that is certainly possible too.

[With mouseover: " 'The light from those millions of stars you see is probably many thousands of years old' is a rare example of laypeople substantially OVERestimating astronomical numbers."]
(Comic source: https://xkcd.com/1342/)

Here's a list of the 300 brightest stars, as seen from Earth (not sure if this list is still up to date, as stars vary in brightness somewhat, but it should suffice as a rough guide). Note the distances in the right-most column.
http://www.atlasoftheuniverse.com/stars.html

 

[snorkack]

Short answers: Yes and yes.

If, with the naked eye, you're looking at something [bright] in the night sky, and it looks like a "star" (i.e., a pinpoint of light), you can bet it's in the Milky Way galaxy and it's relatively close. While thousands of light-years away is possible, hundreds is more likely. Less than that is certainly possible too.

[With mouseover: " 'The light from those millions of stars you see is probably many thousands of years old' is a rare example of laypeople substantially OVERestimating astronomical numbers."]
(Comic source: https://xkcd.com/1342/)

Here's a list of the 300 brightest stars, as seen from Earth (not sure if this list is still up to date, as stars vary in brightness somewhat, but it should suffice as a rough guide). Note the distances in the right-most column.
http://www.atlasoftheuniverse.com/stars.html

Another list, 92 brightest stars:
https://en.wikipedia.org/wiki/List_of_brightest_stars
It has the advantage of being sortable, which the atlasoftheuniverse list is not.
Out of the 92 brightest stars, I count 7 that are over 1000 ly away, the furthest is 2600 (and 2 more at 2000. Note that large distances tend to be less precise). 32 are less than 100 ly away.

 

[FactChecker]

Another list, 92 brightest stars:
https://en.wikipedia.org/wiki/List_of_brightest_stars
It has the advantage of being sortable, which the atlasoftheuniverse list is not.
Out of the 92 brightest stars, I count 7 that are over 1000 ly away, the furthest is 2600 (and 2 more at 2000. Note that large distances tend to be less precise). 32 are less than 100 ly away.

Thanks! That reference also has a link to this (https://en.wikipedia.org/wiki/List_of_brightest_natural_objects_in_the_sky), which helps me to sort out what I can easily see, which are stars, which are galaxies, and what constellation they are in.

 

[OmCheeto]

...

Here's a list of the 300 brightest stars, as seen from Earth (not sure if this list is still up to date, as stars vary in brightness somewhat, but it should suffice as a rough guide). Note the distances in the right-most column.
http://www.atlasoftheuniverse.com/stars.html

Kind of weird how the stars on that list fit a Bell curve almost exactly.
Perhaps I'll turn that into a homework problem, as to why that is.

I wonder if this is how Planck got started developing his curve, sitting at home solving peculiar math problems.

I'm guessing the left side goes up like that because of increasing logarithmic volumes and the right side goes down because of the inverse square law.
Along with some distribution of star brightnesses thrown in to spice it up.

 

[Astronuc]

January 9, 2023 (Phys.org) Astronomers find the most distant stars in our galaxy halfway to Andromeda
https://phys.org/news/2023-01-astronomers-distant-stars-galaxy-halfway.html

Astronomers have discovered more than 200 distant variable stars known as RR Lyrae stars in the Milky Way's stellar halo. The most distant of these stars is more than a million light years from Earth, almost half the distance to our neighboring galaxy, Andromeda, which is about 2.5 million light years away.

The characteristic pulsations and brightness of RR Lyrae stars make them excellent "standard candles" for measuring galactic distances. These new observations have allowed the researchers to trace the outer limits of the Milky Way's halo.

"This study is redefining what constitutes the outer limits of our galaxy," said Raja GuhaThakurta, professor and chair of astronomy and astrophysics at UC Santa Cruz. "Our galaxy and Andromeda are both so big, there's hardly any space between the two galaxies."

Ostensibly, Andromeda and Milky Way galaxies could exchange stars.

Yuting Feng, a doctoral student working with GuhaThakurta at UCSC, led the new study and is presenting their findings in two talks at the American Astronomical Society meeting in Seattle on January 9 and 11.

According to Feng, previous modeling studies had calculated that the stellar halo should extend out to around 300 kiloparsecs or 1 million light years from the galactic center. (Astronomers measure galactic distances in kiloparsecs; one kiloparsec is equal to 3,260 light years.) The 208 RR Lyrae stars detected by Feng and his colleagues ranged in distance from about 20 to 320 kiloparsecs.

 

[Vanadium 50]

Hmmm....

RR Lyrae's are commonly found in globular clusters. So saying what galaxy they are from doesn't quite tell the story.

 

[Ibix]

RR Lyrae's are commonly found in globular clusters. So saying what galaxy they are from doesn't quite tell the story.

Is the underlying issue here that "which galaxy does this star belong to" is a classification problem, not a physics problem? So for edge cases like stars half way-ish between here and Andromeda it depends what (somewhat arbitrary) classification rule you apply and stuff like whether you ever count clusters as separate from a galaxy, etcetera, etcetera, while there's a stable answer for stars in our night sky under any even vaguely sensible rule.

 

[Vanadium 50]

a classification problem, not a physics problem

Lots of things are like this. What is a merger and what is merely mass transfer?

 

[Vanadium 50]

As an aside, there are at least two globular clusters originally misidentified as stars, both mentioned in this thread. There is also an entire galaxy misidentified as a star, BL Lacertae,

 

[snorkack]

There is also an entire galaxy misidentified as a star, BL Lacertae,

Is BL Lacertae a galaxy, or a black hole?
Note that "asteroid" and "quasar" are two different spellings of "star-like". "Aster"-"oid", or "quasi"-"star".

 

[Vanadium 50]

Is BL Lacertae a galaxy, or a black hole?

That distinction makes no sense. It's an active galaxy, and like many galaxies has a central black hole.

 

[snorkack]

Well, "Sagittarius A" is a designation distinct from "Milky Way". What precisely is "Virgo A"? Is it a synonym of "M87", or is it the nucleus as disinct from the surrounding galaxy?
BL Lacertae shares the property with 3C 273 and many other quasars, that the nucleus outshines the surrounding galaxy (in case of 3C 273, by about 3 magnitudes).

 

[Vanadium 50]

Honestly, I think this is a meaningless distinction you are trying to draw. The entire galaxy covers an angular extent comparable to a large star so there is little point in quibbling about parts of the galaxy.

 

[DaveC426913]

Honestly, I think this is a meaningless distinction you are trying to draw. The entire galaxy covers an angular extent comparable to a large star so there is little point in quibbling about parts of the galaxy.

I see your point.

This wiki entry seems to read as if BL Lac is an entity implicitly distinct from what it refers to as its "host" galaxy - but in the context of the OP question that's a pretty moot point. As a sky object, it's a single object.

 

[snorkack]

Honestly, I think this is a meaningless distinction you are trying to draw. The entire galaxy covers an angular extent comparable to a large star so there is little point in quibbling about parts of the galaxy.

The biggest stars are R Doradus and Betelgeuse, around 5 centiseconds across. Which means about 1 in 4 millions. At the 280 Mpc distance of BL Lac, this makes around 70 pc. Is the galaxy really that small?
But an example about ambiguity of what you see is the Sword of Orion.
The brightest components are:
θ¹ C is +5,13
θ¹ A and D are +6,7, B +7,9, all of them within half a minute of C. (Other stars are below +10)
θ² A is +5,02
θ² B is +6,4 and C +8,2. And those are slightly more separated than the θ¹ components.
θ² A and θ¹ C are bright enough that you might see them as single stars, and θ² A is the slightly brighter of these. But since θ¹ C has more companions with tighter separations, these sum up to a brighter visible spot. So what do you really see? A cluster, or the brightest star of the cluster?

 

[Vanadium 50]

This is quibbling, nad IMO unhelpful to the OP.

Is there any doubt that the angular extent of BL Lac is much, much, much closer to that of R Doradus than ω Cen?