'One of the greatest damn mysteries of physics': We studied distant suns in the most precise astronomical test of electromagnetism yet

"From these exquisite spectra, we have shown that α was the same in the 17 solar twins to an astonishing precision: just 50 parts per billion. That's like comparing your height to the circumference of Earth. It's the most precise astronomical test of α ever performed. Unfortunately, our new measurements didn't break our favorite theory. But the stars we've studied are all relatively nearby, only up to 160 light-years away."

My observation. Various reports through the years show efforts to test alpha, the fine-structure constant and find some variation perhaps :) Here is an example from 2004:

New Quasar Studies Keep Fundamental Physical Constant Constant, https://ui.adsabs.harvard.edu/abs/2004eso..pres....5./abstract, March 2004. "...PR Photo 07/04: Relative Changes with Redshift of the Fine Structure Constant (VLT/UVES) A fine constant To explain the Universe and to represent it mathematically, scientists rely on so-called fundamental constants or fixed numbers. The fundamental laws of physics, as we presently understand them, depend on about 25 such constants. Well-known examples are the gravitational constant, which defines the strength of the force acting between two bodies, such as the Earth and the Moon, and the speed of light. One of these constants is the so-called "fine structure constant", alpha = 1/137.03599958, a combination of electrical charge of the electron, the Planck constant and the speed of light. The fine structure constant describes how electromagnetic forces hold atoms together and the way light interacts with atoms. But are these fundamental physical constants really constant? Are those numbers always the same, everywhere in the Universe and at all times? This is not as naive a question as it may seem. Contemporary theories of fundamental interactions, such as the Grand Unification Theory or super-string theories that treat gravity and quantum mechanics in a consistent way, not only predict a dependence of fundamental physical constants with energy - particle physics experiments have shown the fine structure constant to grow to a value of about 1/128 at high collision energies - but allow for their cosmological time and space variations. A time dependence of the fundamental constants could also easily arise if, besides the three space dimensions, there exist more hidden dimensions..."

There is always the issue of fine-tuning of the universe and the origin of the universe we see today in astronomy.

How do we know the fundamental constants are constant? We don't., https://forums.space.com/threads/how-do-we-know-the-fundamental-constants-are-constant-we-dont.59359/
 
I'm curious which stars were found to be solar twins. At one time, 18 Sco was the best solar twin, but another one was found to be better.

Observing these stars will demonstrate the Sun's non-yellow (or orange as in this article) color. But, at times, they can also appear with a tint of yellow or gold. These color variations are strong indicators of high atmospheric particle counts. I suspect this may corelate to seeing conditions, which is helpful to know before serious observing.

Is this likley?
 
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These stars can be used to demonstrate the Sun's non-yellow (or orange, as it is described in this article) tint. But occasionally they might also have a golden or yellow hue to them. Strong signs of high atmospheric particle counts are these colour variations. Before engaging in any serious watching, it would be nice to know if this had anything to do with the seeing conditions.
 
These stars can be used to demonstrate the Sun's non-yellow (or orange, as it is described in this article) tint. But occasionally they might also have a golden or yellow hue to them. Strong signs of high atmospheric particle counts are these colour variations. Before engaging in any serious watching, it would be nice to know if this had anything to do with the seeing conditions.
I agree. 😏
 
Nov 10, 2020
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I'm curious which stars were found to be solar twins. At one time, 18 Sco was the best solar twin, but another one was found to be better.

Observing these stars will demonstrate the Sun's non-yellow (or orange as in this article) color. But, at times, they can also appear with a tint of yellow or gold. These color variations are strong indicators of high atmospheric particle counts. I suspect this may corelate to seeing conditions, which is helpful to know before serious observing.

Is this likley?
Its tricky to define the Sun's solar relatives after all as far as we can tell relatively massive "lower mass stars, i.e. F and G type main sequence stars, like our Sun only form in dense star formation clusters the type where very massive stars form something we have evidence to support in terms of the presence of fossilized chemical bonds from short lived radioisotopes from the Early solar system with different chemistry to their daughter products (basically elements in chemical bonds that the current element wouldn't form but which a radioisotope that decays into that element does suggesting that when the molecules in "primordial" asteroid, meteor and or cometary derived material formed the short lived radioisotope was present).

Adding to that work which has combined GAIA astrometry with spectroscopic data has shown that the Sun formed near the tail end of the Milky Way's most intense starburst event linked to the disk plunging collision of the Sagittarius Dwarf Spheroidal galaxy. If the GAIA sample of stars is broadly representative of the galaxy at large that suggests that well over 50 percent of the stars that the Milky Way galaxy has ever formed formed during that billion year starburst episode in this case differentiating the Sun from other stars by age is likely a daunting task. Its even quite possible that the Sun may have formed in a now tidally disrupted super star cluster like those we observe in the LMC during its own starburst episode.

Given that the Sun likely has tens of thousands of siblings at least even though the vast majority of the remaining stars will be less massive K and M type main sequence stars which will naturally fail to meet the solar twin criteria there will still be a lot of G type stars that meet that criteria and because the chaotic inhomogeneous conditions in starbursts even stars from the Sun's birth cluster may vary considerably in chemical composition.

Then of course you get to the issue of stellar migration since we have some evidence to suggest the Sun likely formed closer to the Galactic center than it is found now which isn't surprising given that stars are locked within an angular momentum constrained random walk of sorts which over time via stellar encounters and interactions with passing density waves tidal perturbations etc. which all can cause shifts in a star's orbit around the Milky Way. This makes it difficult to trace back the Sun yet alone any of its siblings to their place of origin as there have been nearly 5 billion years of jumbled mixing with the general disk population. Its not impossible per say especially if you have a big enough data set of say every star's spectrum in the Milky Way but it is tricky

Hence its a far more complex question than people tend to think. On one hand though if the Sun has millions of siblings finding stellar twins might be surprisingly easy its just verifying them would be hard.
 
Its tricky to define the Sun's solar relatives after all as far as we can tell relatively massive "lower mass stars, i.e. F and G type main sequence stars, like our Sun only form in dense star formation clusters the type where very massive stars form something we have evidence to support in terms of the presence of fossilized chemical bonds from short lived radioisotopes from the Early solar system with different chemistry to their daughter products (basically elements in chemical bonds that the current element wouldn't form but which a radioisotope that decays into that element does suggesting that when the molecules in "primordial" asteroid, meteor and or cometary derived material formed the short lived radioisotope was present).
Yes, but yet there are "solar twins" that are surprisingly close in all features, including composition. This would allow a close spectral comparison.

Roughly 4% or 5% of the stars in the galaxy are G-type. If only 4% or 5% of those are G2, then there may be as many as 200M G2 stars out there. Maybe 1/3 of those can be observed, leaving maybe 50 million or so. Deduct from those the time frame, as you mentioned.

So, some may have very similar composition. Those that are similar (not very similar) are called solar analogs. The very similar are the "twins".

Given that the Sun likely has tens of thousands of siblings at least even though the vast majority of the remaining stars will be less massive K and M type main sequence stars which will naturally fail to meet the solar twin criteria there will still be a lot of G type stars that meet that criteria and because the chaotic inhomogeneous conditions in starbursts even stars from the Sun's birth cluster may vary considerably in chemical composition.
There was a report I read a while back, but I don't think I saved it, that explained that the no. of siblings might be between 1000 and 3000. The upper constraint was due to the claim that the outer planets would have encountered more orbital instability due to perturbations from the close neighbors.

The IMF (Initial Mass Function) seems to show about 60 stars out of 3000 that would have masses between 0.9 and 1.1. So, perhaps there are a few solar twins from our own original GMC.

Then of course you get to the issue of stellar migration since we have some evidence to suggest the Sun likely formed closer to the Galactic center than it is found now which isn't surprising given that stars are locked within an angular momentum constrained random walk of sorts which over time via stellar encounters and interactions with passing density waves tidal perturbations etc. which all can cause shifts in a star's orbit around the Milky Way. This makes it difficult to trace back the Sun yet alone any of its siblings to their place of origin as there have been nearly 5 billion years of jumbled mixing with the general disk population.
All good points. I do recall U of Texas, however, finding one sibling, though I don't recall its type.

I must admit I don't really understand the crux of their argument. There are over 25,000 lines in the solar spectra. How many must they match with another star? Can't they pick the ones that match the most evident atoms, say a certain iron ion, to get their verification? If the constant they wish to confirm is not constant, wouldn't it be seen in those dozen lines or so for one atom?
 
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Yes, but yet there are "solar twins" that are surprisingly close in all features, including composition. This would allow a close spectral comparison.

Roughly 4% or 5% of the stars in the galaxy are G-type. If only 4% or 5% of those are G2, then there may be as many as 200M G2 stars out there. Maybe 1/3 of those can be observed, leaving maybe 50 million or so. Deduct from those the time frame, as you mentioned.

So, some may have very similar composition. Those that are similar (not very similar) are called solar analogs. The very similar are the "twins".

There was a report I read a while back, but I don't think I saved it, that explained that the no. of siblings might be between 1000 and 3000. The upper constraint was due to the claim that the outer planets would have encountered more orbital instability due to perturbations from the close neighbors.

The IMF (Initial Mass Function) seems to show about 60 stars out of 3000 that would have masses between 0.9 and 1.1. So, perhaps there are a few solar twins from our own original GMC.

All good points. I do recall U of Texas, however, finding one sibling, though I don't recall its type.

I must admit I don't really understand the crux of their argument. There are over 25,000 lines in the solar spectra. How many must they match with another star? Can't they pick the ones that match the most evident atoms, say a certain iron ion, to get their verification? If the constant they wish to confirm is not constant, wouldn't it be seen in those dozen lines or so for one atom?
Not necessarily after all the evidence we have that alpha isn't constant always comes from particle accelerators which seems to suggest the strength of alpha is energy dependent at least at the high energies of quark gluon plasma, if there is an energy dependence than selection of stars based on similar spectra could be biased since those stars would also presumably be of similar temperatures of which both spectral line expression and black body radiation curves are dependent. I.e. elemental spectral lines depend not only on the abundance of an element but the amount of that element getting energetically excided enough to emit or absorb light. Thus its possible that you might be implicitly biasing results.

And yeah I think there have been a few such candidates found over the years or at least reported candidates not sure if any have ever been veritably confirmed(if we are even capable of such a confirmation).
 
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Not necessarily after all the evidence we have that alpha isn't constant always comes from particle accelerators which seems to suggest the strength of alpha is energy dependent at least at the high energies of quark gluon plasma, if there is an energy dependence than selection of stars based on similar spectra could be biased since those stars would also presumably be of similar temperatures of which both spectral line expression and black body radiation curves are dependent. I.e. elemental spectral lines depend not only on the abundance of an element but the amount of that element getting energetically excided enough to emit or absorb light. Thus its possible that you might be implicitly biasing results.
Yes, temperature is very important, and maybe I’m being too pedantic for a general article, but wouldn’t a solar analog work for their purposes? I assume the absorption lines are not dependent on the other lines of other elements. But perhaps density and other parameters will vary with composition.
 
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Yes, temperature is very important, and maybe I’m being too pedantic for a general article, but wouldn’t a solar analog work for their purposes? I assume the absorption lines are not dependent on the other lines of other elements. But perhaps density and other parameters will vary with composition.
I would think so personally but the key thing for doing good science though is you need to keep in mind potential sources of bias which could influence results meaning you should prepare for the possibility of bias to at the very least rule it out if possible.
Scientists are human thus we suffer the same flaws as other people which means that even if we try and account for every bias we can think of some can and probably will show up to blindside us.
 

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