Thread: how many stars are there compared to "naked eye" c

Simple question: "how many stars are there, really, compared to what we observe wih the naked eye on a clear non-moon filled night somewhere north of the equator, high up away from urban development"?

Like, "what's the ratio of what we see with our naked eye to what the hubble can see, the figure, the number, what:what"?

Is it, like, 1:1000, what we see with our naked eye compared to what actually exists.

And if I may, "is there evidence that telescopes have found a limit to what tey can see of stars?": "have telescopes been able to find a dead zone, a dead outer limit where there appears to be no stars?"

Telescopes can't see any stars further back then the surface of last scattering. Which is essentially the big bang itself.

The naked eye can see roughly several thousand stars. In our galaxy, there are roughly 200 Billion stars. And there are approximately 35 galaxies in the local cluster. And there are approximately 100 clusters in the Virgo Supercluster. And there are millions of super clusters that we can see.

So the actual ratio is... quite large.

First, thank you for your response.

Now, if I may: I read a report that stated scientists in using the Hubble were able to see stars they never thought existed, clustered in a manner that suggested there's even more further back than what their telescopes can clearly pick up. That right out tells one that there is no proof yet of the limit to what we can perceive in space. Any ideas?

I'm not familiar with the specifics, but there's probably a gap between the earliest stars and the surface of last scattering. Maybe they found some stars closer to the surface of last scattering than they thought possible/ever saw before. You shouldn't see any stars further back than that. If you did, that would be a pretty big nail in the coffin for the big bang theory.

That seems quite odd to me. Maybe a reference to that article might help. It is often said that the Supernovae of the first stars might be visible with the James Webb telescope to be launched 2013 the earliest. But even this is not really true. The final limit of course is the background radiation. It is impossible to penetrate that with electromagnetic radiation. Hubble can only look as far as a few redshift units. So, I am puzzled. Maybe they were talking about microlensing?

At present there is a rough estimate of 7 x 10^22 stars (that's 22 noughts). Most of them are so far away that even for Hubble, tens to hundreds of billions of stars are represented by mere blobs, even specks at the limits of it's magnification.

There is a "void" found recently which is a billion light years across and has almost nothing in it.

There are actually quite a few voids. Check out this map of the universe.

A good image. 3 voids mentioned there though the scale is such that it does not show how vacant the voids are (our galaxy would not be visible on such a scale). We are told inflation happened so we have an homogeneous universe but reality says it is not homogeneous with voids and walls of galaxies. It may just be my eyes joining up the dots but there does seem to be a hint of a honeycomb structure.

Originally Posted by Dishmaster

That seems quite odd to me. Maybe a reference to that article might help. It is often said that the Supernovae of the first stars might be visible with the James Webb telescope to be launched 2013 the earliest. But even this is not really true. The final limit of course is the background radiation. It is impossible to penetrate that with electromagnetic radiation. Hubble can only look as far as a few redshift units. So, I am puzzled. Maybe they were talking about microlensing?

(hoping your reply was in response to my remarks)

The report I read was self-evident. It is self-evident that Hubble has actually picked-up stars not previously visible to previous telescopes. My point was that if a more powerful telescope was able to pick up new stars not previously visible, what certainty do we have that telescopes more powerful than the Hubble (in the future)can or can't pick up even more further/distant stars?

It's not a distance issue, it's a faintness issue.

Some stars are very bright. We can see them from other galaxies. Some are quasars, some are supernova, but they are very bright. We could probably see a supernova exploding at the edge of the visible universe.

Some stars are less bright, such as the brown dwarfs. We can barely see them at all with modern technology, because they are so dim. They have to be within a range of maybe dozens to hundreds of light years.

The difference between these objects is brightness, called the apparent magnitude. Better telescopes allow us to see objects of higher apparent magnitude (dimmer, because they're less bright or further away).

Originally Posted by theQuestIsNotOver

The report I read was self-evident. It is self-evident that Hubble has actually picked-up stars not previously visible to previous telescopes. My point was that if a more powerful telescope was able to pick up new stars not previously visible, what certainty do we have that telescopes more powerful than the Hubble (in the future)can or can't pick up even more further/distant stars?

Up to a certain distance, it is evident that larger or more sensitive telescopes can discover more stars than the generation before. Compared to the latest ground-based telescopes, the HST is already quite outdated. It's only advantage is still that it is not affected by the atmosphere diluting the light from the stars.

A fundamental physical law tells us that the farther away an object is the fainter it appears. Therefore, it is obvious that more sensitive telescopes can look at larger distances. However, the redshift vs. distance relation also shifts the starlight into the red spectral range, so that very distant normal stars can only be detected in the Infrared. This is why new space telescopes like Herschel or James Webb are built.

The final borderline will be a distance that corresponds to the age (distance = lookback time) where the first stars were formed. They have not been observed yet, and it will take probably a few decades more until we can. The standard Big Bang theory predicts a zone void of stars between the first generation of stars and the age of recombination, when the universe became transparent which we now see as the microwave background radiation. So, the future telescopes will be able to corroborate or falsify the Big Bang theory, depending on whether they find this gap or not.

Thank you for your reply.

I understand what you are explaining. I understand your explanation. But I have another question": the map of the Universe, as it exists in the here and now, if the Universe had a "now-continuum", that's not the picture the stars paint, is it"?

For instance, lets say a star nearby is actually the oldest star in the universe, and stars distant, further out, are younger, but didn't have what it took to live like this ACORN tree star...........just a little star distant to this one from our reference, that came into existence and then faded. It's a possiblility, but we discount it, no?

Keep in mind because of the finite speed of light if we are looking at an object 13 billion light years away, we're looking at what it looked like 13 billion years ago. We don't know what it looks like "now" (though this is a debatable concept if you use relativity), just what it looked like a long time ago, dependent on how far away it is.

Yes, agreed. So there is no real way of telling what the real map of the Universe is?

No. In fact modern theory pretty much says it's impossible. At least from direct observation. You could always make educated guesses using computer models.

That's what I think as well. But ask anyone in the street and they would think all their investment, all the taxes they pay, to astronomical observation, is a sure bet. I would be more inclined to take a church's point of view about how realistic the stars are........that if we all work together as one in harmony we might actually achieve something (pipe dream).

(edit): I hope that maybe there is an answer to being realistic about the stars as opposed to looking into some type of warped time machine that could in fact be a reflection, a lensing, continual, of only a handful of stars compared to what we think is out there.........maybe only one star? In fact, what "good" is a theory about the stellar time machine we see as the universe of stars at night? Could not the laws of physics "change" in time, could not there be some "rusting" of the fabric of space-time, if not "development". Point being, can we rely on astro-physics as a reliable way to account for our own atomic phenomena on this planet in the here and now?

Originally Posted by theQuestIsNotOver

That's what I think as well. But ask anyone in the street and they would think all their investment, all the taxes they pay, to astronomical observation, is a sure bet. I would be more inclined to take a church's point of view about how realistic the stars are........that if we all work together as one in harmony we might actually achieve something (pipe dream).

(edit): I hope that maybe there is an answer to being realistic about the stars as opposed to looking into some type of warped time machine that could in fact be a reflection, a lensing, continual, of only a handful of stars compared to what we think is out there.........maybe only one star? In fact, what "good" is a theory about the stellar time machine we see as the universe of stars at night? Could not the laws of physics "change" in time, could not there be some "rusting" of the fabric of space-time, if not "development". Point being, can we rely on astro-physics as a reliable way to account for our own atomic phenomena on this planet in the here and now?

It's possible the laws of physics drift over time. We don't have enough evidence to make a reasonable guess at the answer. But if we assume that the laws of physics are universal across all time and space, we can construct theoretical models which can explain the vast majority of observable data.

The rest of my reply is what I just said in this post.

But to clarify my interest in this subject, if we are going to be serious about the term "reasonable theory of the Universe", we should make a decison on whether the laws of space-time are "universal" or that they erode in time.

For instance, if we said that the laws of physics did not erode in time, that they applied to all of what we "observe" of space-time as per our interest in the stars, can we not then make the "big-bang" an "axiom" of cosmology, of astronomy? Can we not therefore create a mathematical precedent that does the big-bang "justice" when it comes to financing our efforts of interest in the stars? How we can substaiate stellar investments without doing the math on certainties we call "more than reasonable doubt theories"?

String theory spends its effort trying to understand the universe from first principles, from a mostly purely mathematical basis. When done, it would explain the underlying why of the big bang, or present another model which explains the data just as well or better. That sounds like what you're after. With such a theory in hand, the big bang would be a mathematical proof (not an axiom, but just as "true". Not something you could dispute if the axioms are true).

Of course, it's been 30+ years of work with nothing much to show for it. And it's not just time. A lot of public money from universities has been funneled into string theory development. So IMO it's a waste of resources to get involved in that sort of scientific realism. Much cheaper to just make theories explaining data and then test them.

The big bang might be disproven some day, and then we'll try to figure out a better model. But it does an excellent job at the moment of explaining the observable universe.

I am not shopping for ideas. I donot live in hope. If I have an idea I can call my own, it will based on the "dead" and what they have done. I hate competing with those alive. I'd rather give them the microphone. My interest here is not necessarily a reassurance of doubt I have, it would seem, in our "best efforts", but a "hope" we can do better, and be so "pop", so "fantasy driven", about what we know.

Which is why I ask these questions.

Theory should be self-evident after exposing charletons. In this world, with all the time we have had in debating what reality is, our "task" if we take our tooling of science seriously, science of the past, is to de-bunk any crap people can carry on with and to accept the most "up to date facts we have" as a "first principal entity" contestant. Surely our ancients would approve of being considered as those who merely inspired an new "ultimate" theory, given the facts they depended o back then?

I'm not sure I understand the point you're trying to make anymore. Do you view the current big bang cosmology as "good" science? Or is it a charleton representing "bad" science?

You cut to the chase well.

Neither. As I said, I prefer to ask questions. I will keep asking questions even when people think I have come to an answer. My belief is simple: if you can ask a question on an issue, well, you have honored someone in doing more than trying to understand them....you have gone one better in asking a sincere question. If their paranoia steps in, like they dont know the subject, it will become apparent. What happens next is not guesswork.

Ah, well good. We need more question askers Just don't let people handwave their way out of things. My philosophy is if you can't explain the broad strokes to a 5th grader you don't really understand it.

I guess then if I were to compare myself to a 5th grader, I would feel you have done me justice in leaving this conversation. My questions are not based on being illeterate and savvy. God only hopes also, I pray. I ask questions in the context of knowing what "good investment" is, I hope, otherwise I may as well be living in some parallel universe.

Let me get back to the idea of the possibility of changing physical laws.

The currently accepted theory of the "Big Bang" is based on the assumption that the universe is on average homogeneous and isotropic. This means, it is the same everywhere and looks the same from everywhere - always on average of course. This should also include the perspective backwards in time. Without this assumption, all current cosmological or even astronomical research would be rather pointless, because there would be no hope of discovering the fundamentals of the universe.

In fact, there is a lot of evidence that at least the observable universe indeed behaves that way. One is that all observable stars can be well categorised by its spectral properties - regardless of their distance from us. They all seem to show the same basic chemistry. Even the most distant objects show the same spectra, even though the spectral lines are shifted into the red spectral range. Nevertheless, the "chemical fingerprints" are the same everywhere.

Furthermore, the current knowledge of physics is at least able to reconstruct a model of the evolution of the universe back to a few moments after the hypothesised Big Bang. This does not prove the underlying theory right, but at least reality does not seem to contradict it, so continuity of physical laws seems very likely.

I could add a few more indications, all leading to a coherent picture that the fundamental laws of physics - regardless of how much we currently understand - have not changed (noticeably) since the beginning of the universe.

There are, however, a few indications that some fundamental physical constants could have changed in time. But the underlying results are very speculative and surely need much more investigation.

sounds like a "babe".

nothing wrong with that.

knowing a babe does much for one's "story-telling" confidence, no?

"babe" or ""babe" or something else?

Bringing up a child is often compared to a "theory".

You educate it with what you know, you hope it works out for you, ya-di-ya-di-ya-da.

Apologies for the confusion.

no worries