Ask Me Anything AMA with Dr Joe - Feb. 7th

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rod

Oct 22, 2019
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Dr. Joe, what is your thinking about some new reports on the solar system evolving from a 3 ring protoplanetary disk, some examples are cited using stars observed by ALMA but HL Tauri and GM Aurigae contain very large disks too.

Here are two recent reports on the 3 ring protoplanetary disk model reported for our solar system.



Just to compare, here is the 1977 MMSN model proposed, The Distribution of Mass in the Planetary System and Solar Nebula, https://ui.adsabs.harvard.edu/abs/1977Ap&SS..51..153W/abstract

Much has changed now in the studies of ALMA and various simulations used.

Dr. Joe et al. Space.com published their report on the ring model too, The sun used to have rings like Saturn, https://forums.space.com/threads/the-sun-used-to-have-rings-like-saturn.53464/
11-Jan-2022.
 
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Nov 16, 2020
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Joe... Why hasn't Perserverance Rover on Mars analyzed any of the sediments in the lake bed where it landed? Sending postcard landscapes home is fine but doesn't help the search for life. There should be evaporite mineral there after the water dried up.
 
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Given all the advances in space scopes, but also in advances for amateur imaging, do you have any strong views on where serious amateurs who might be splurging on new gear should be considering? We plan to have a dome behind the new house we are building and I'm wondering what opportunities, perhaps pioneering ones, might offer the "best squeeze for the juice". :)

Exoplanetary work looks interesting. Especially the ones more earth-like around G-class stars. But when I calculate the transit time for Earth, as seen from far away, it is 13 hours. This lengthy time would take at least three nights of observing, and over 3 years to capture the profile, not that others at different longitudes couldn't work together, I suppose. Of course, the fast, big ones would still be interesting, but that's a lot of work, I fear.
 
Can you help us understand halo orbits at Lagrange points? I understand why craft like SOHO at L2 needed a halo orbit in order to transmit without having that bright object directly behind it fouling the transmission, but what is the need for a halo orbit at L3? I picture these points as spacetime dimples or gentle "wells" but why not just sit at the bottom of the well rather than circle it?
 
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Hi Astronomy Fans!!

I'm back! It seems I can't stay away; your questions and enthusiasm are so great.

Looking forward to sharing more great astronomy with you.

Dr Joe
Hi Joe,
Why hasn't NASA or some other space agency like ESA or the Chinese Space Agency made another version of the Labelled Release Experiment on the Viking landers that seemed to have some positive indications in the search for microbial life on Mars. I heard Gilbert Levin who developed this experiment and just passed away recently was quite frustrated there wasn't further use of it on say Curiosity, Perseverance of the European or Chinese Mars landers.
 
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Nov 16, 2020
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Hi Joe,
Why hasn't NASA or some other space agency like ESA or the Chinese Space Agency made another version of the Labelled Release Experiment on the Viking landers that seemed to have some positive indications in the search for microbial life on Mars. I heard Gilbert Levin who developed this experiment and just passed away recently was quite frustrated there wasn't further use of it on say Curiosity, Perseverance of the European or Chinese Mars landers.
Maybe because there has been no further evidence of any microbial life on Mars. What will be required are some preserved carbonaceous "fossils", not just metabolic products that could be abiotic. Even they will require some evidence that they came from a microbe. Fossil organic matter a billion years old.
 
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Dec 5, 2021
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What would happen if our solar system was 1 or 10 or 100 lightyears from a two black hole collision
that create these gravity waves we detect in our LIGOs ?
 
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Jzz

May 10, 2021
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Why is the night sky dark?
Dr. Joe. A much cherished belief, especially of children, is that we should be able to find our way using just starlight. Unfortunately, when we actually do venture out on a moonless light, the reality is far different and the available starlight is not enough to light the way. The question is why? Even a very cursory mathematical calculation should show that, given that light travels forever and the sheer number of stars in the Universe, unless something gets in its way, that the night sky should be much brighter than it actually is. Light should accumulate and reinforce itself till the night sky should be as bright as day. Why is that not the case? The present theory that it is the expansion of the Universe that is shifting stars and galaxies away from us and that is why the sky is dark at night, is simply too theoretical and simply to far from our experienced reality. Wouldn’t a far more acceptable explanation for why the night sky is dark be that our notion of how light travels is wrong? Light does not travel forever, just like any wave, think of waves in water or sound waves, light travels until the original energy which created the light can no longer sustain its existence and then it fades away and returns into the medium from which it came. When one thinks of dark matter and the fact that it allows all electromagnetic radiation to travel through itself without offering the slightest resistance, one realizes that dark matter possesses exactly the same properties that the aether was once thought to possess.
 
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DrJoePesce

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Dr. Joe, what is your thinking about some new reports on the solar system evolving from a 3 ring protoplanetary disk, some examples are cited using stars observed by ALMA but HL Tauri and GM Aurigae contain very large disks too.

Here are two recent reports on the 3 ring protoplanetary disk model reported for our solar system.



Just to compare, here is the 1977 MMSN model proposed, The Distribution of Mass in the Planetary System and Solar Nebula, https://ui.adsabs.harvard.edu/abs/1977Ap&SS..51..153W/abstract

Much has changed now in the studies of ALMA and various simulations used.

Dr. Joe et al. Space.com published their report on the ring model too, The sun used to have rings like Saturn, https://forums.space.com/threads/the-sun-used-to-have-rings-like-saturn.53464/
11-Jan-2022.
Hi Rod - Aren't those protoplanetary disks wild? There are several views of why there are gaps in them: One is the ice boundary view, and the other is that the gaps are being swept clean of material by newly formed planets. My colleagues in this area tell me the latter is gaining broader acceptance (though both are likely to be operating in any given disk).

I would be very surprised if our solar system didn't look like what ALMA has detected. For example:

https://www.space.com/infant-stars-planet-forming-disks-images.html
 

DrJoePesce

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Dr Joe, I am quite intrigued by the fact that blackholes' masses are measured by gravitational lensing, as I read in this following recent article in Space.com, can you please explain it better to me and how exactly it works?


The great questions continue! Thanks IG2007. In a nutshell, a gravitating mass bends light as the light passes near the mass. The greater the mass (or the more extreme the gravitational field - as in a black hole), the more the bending. (This was what was used to make the first validation of Einstein's Theory of Relativity, in 1919: https://www.space.com/37018-solar-eclipse-proved-einstein-relativity-right.html )

The mass bending the light is said to be acting as a gravitational lens, and it acts exactly like an optical lens: Light from a distant object is bent (focused) and magnified.

So, if a black hole happens to be between us and a background light source (a distant star, say), and we are looking, the black hole will lens the star and we might see it flicker and increase in brightness as the black hole moves in front of it. From the equations that define the gravitational lens, we can measure the mass of the lens, and if it's more than about 3 times that of the Sun but isn't emitting electromagnetic radiation, it's almost certainly a black hole. This phenomenon is also known as "microlensing" to differentiate from gravitational lensing caused by much larger objects such as galaxies or clusters of galaxies. One of my most favorite images is of the central region of a rich cluster of galaxies, Abell 370 - here from Hubble:

https://hubblesite.org/contents/media/images/2017/20/4024-Image.html

Almost every object in the image is a galaxy within the cluster. The streaks and smears of light are gravitational lensed images of more distant galaxies ("behind" Abell 370), lensed by the enormous mass of the cluster itself.
 

DrJoePesce

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Joe... Why hasn't Perserverance Rover on Mars analyzed any of the sediments in the lake bed where it landed? Sending postcard landscapes home is fine but doesn't help the search for life. There should be evaporite mineral there after the water dried up.
Hi Broadlands, I'm afraid that is way outside my area of expertise (both science and rover exploration strategy).
 
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DrJoePesce

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Given all the advances in space scopes, but also in advances for amateur imaging, do you have any strong views on where serious amateurs who might be splurging on new gear should be considering? We plan to have a dome behind the new house we are building and I'm wondering what opportunities, perhaps pioneering ones, might offer the "best squeeze for the juice". :)

Exoplanetary work looks interesting. Especially the ones more earth-like around G-class stars. But when I calculate the transit time for Earth, as seen from far away, it is 13 hours. This lengthy time would take at least three nights of observing, and over 3 years to capture the profile, not that others at different longitudes couldn't work together, I suppose. Of course, the fast, big ones would still be interesting, but that's a lot of work, I fear.
Hi Helio - that's a great thing to plan! I'm afraid I haven't kept up with the technology, but there are lots of resources - from reputable sources - on the internet. As you note, the technology accessible is phenomenal and would allow you to do all sorts of things: From astrophotography to meaningful research.

Yes, exoplanet research is going to be difficult with whatever tech you have. Lots of projects available, though. Look into activities conducted by your local amateur organization, for example. Through your local organization you can access the Astronomical League (https://www.astroleague.org/) which has an observing program resource page: https://www.astroleague.org/observing.html (and links therein).

And, of course, there is the American Association of Variable Star Observers - AAVSO: https://www.aavso.org/

Good luck!
 

DrJoePesce

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Can you help us understand halo orbits at Lagrange points? I understand why craft like SOHO at L2 needed a halo orbit in order to transmit without having that bright object directly behind it fouling the transmission, but what is the need for a halo orbit at L3? I picture these points as spacetime dimples or gentle "wells" but why not just sit at the bottom of the well rather than circle it?
You are stretching my limits here, Helio! I point you to the excellent blog site/entry for the JWST:

https://blogs.nasa.gov/webb/2022/01/21/webbs-journey-to-l2-is-nearly-complete/

(I'm sure you are aware of this website, but if you aren't it's worth exploring .)

From the page I linked:
And because L2 is a location of gravitational equilibrium, it is easy for Webb to maintain an orbit there. Note that it is simpler, easier, and more efficient to orbit around L2 than to dwell precisely at L2. Furthermore, by orbiting rather than being exactly at L2, Webb will never have the Sun eclipsed by Earth, which is necessary for Webb’s thermal stability and for power generation.
I know it doesn't really give the full "why" info, but it alludes to the reason.
 

DrJoePesce

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Hi Joe,
Why hasn't NASA or some other space agency like ESA or the Chinese Space Agency made another version of the Labelled Release Experiment on the Viking landers that seemed to have some positive indications in the search for microbial life on Mars. I heard Gilbert Levin who developed this experiment and just passed away recently was quite frustrated there wasn't further use of it on say Curiosity, Perseverance of the European or Chinese Mars landers.
Hi newworldsexplr, I'm afraid I can't answer this one either! So sorry I'm not able to satisfy your curiosity - but it happens! 🙂
 
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rod

Oct 22, 2019
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Hi Rod - Aren't those protoplanetary disks wild? There are several views of why there are gaps in them: One is the ice boundary view, and the other is that the gaps are being swept clean of material by newly formed planets. My colleagues in this area tell me the latter is gaining broader acceptance (though both are likely to be operating in any given disk).

I would be very surprised if our solar system didn't look like what ALMA has detected. For example:

https://www.space.com/infant-stars-planet-forming-disks-images.html
"Aren't those protoplanetary disks wild?" Yes Dr. Joe, wild is a good description. Reports of gaps in disks caused by new planets has other answers too. A new report indicates radiation pressure could be doing this and causing dust to migrate in the disk. Dust Dynamics in Transitional Disks: Clumping and Disk Recession,
https://arxiv.org/abs/2202.02328, "The role of radiation pressure in dust migration and the opening of inner cavities in transitional disks is revisited in this paper..." Reference paper, https://arxiv.org/pdf/2202.02328.pdf, 08-Feb-2022, Dust Dynamics in Transitional Disks: Clumping and Disk Recession, 04-Feb-2022.

I think there are more issues with computer models claiming to show how disks observed around some stars evolve into planets than commonly reported. “1. INTRODUCTION Transitional disks are characterized by the depletion of dust in their central regions. However, the origin of those inner cavities is still uncertain. Recent surveys on transitional disks by Atacama Large Millimeter/Submillimeter Array (ALMA) and Australia Telescope Compact Array (ATCA) suggest that the cavities are cleared by planets in the disk (e.g., van der Marel et al. 2018; Francis & van der Marel 2020; Norfolk et al. 2021). However, evidence shows that planets may not be the only explanation for these cavities...Therefore, we want to seek for other possible mechanisms to clear the cavity in transitional disks."

Consider the recent reports of 3 rings used for our solar system citing ALMA observations and the 1977 MMSN model. Modeling how the disks evolve into new planets, and eventually new people :) Is a work in progress :)

An additional thought. Perhaps someday I may see a site showing the stars with disks reported showing various properties, e.g. disk mass, dust and gas. A good example is exoplanet reporting sites I use. The Extrasolar Planets Encyclopaedia (exoplanet.eu) and NASA Exoplanet Archive (caltech.edu)

When I research this topic, I use the arxvi.org site and NASA ADS Abstract site but this is tedious and time consuming to read the papers published now on the topic :)
 
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I suspect I have already asked this in the past, but in case I haven’t... In my prior hunt for demonstrable evidence for the Sun’s true color - as seen in space properly attenuated - I have enjoyed learning about the physics of color that appears for many reasons (Rayleigh scattering, refraction, atomic emissions, etc.). For example, and related to my forthcoming question, the rich blue color that occasionally appears for most of Saturn’s northern hemisphere is a site to see. [This happens, apparently, due to a clearing effect that allows more Rayleigh scattering.]

Given the likelihood that the range of the number of nascent stars in the early solar neighborhood is about 1,000 to perhaps as many as 3,000 stars, per an earlier paper (IIRC), we would therefore likely have a couple of massive stars having formed, thanks to the application of the IMF (Initial Mass Function). As a result, a significant number of our new neighbors would also be extremely bright and would provide significant illumination upon our early solar accretion disk.

All of the above is to see if you know of anyone or paper that has addressed the possibility that such accretion disks would not look as artists color them but, like Saturn - blue to the human eye?

My suspect math indicates that a few bright neighbors could provide enough light to allow our photopic (color) vision to see color if it’s there. The disk being > 99% gas, and with the larger grains residing more in the middle, suggests to me we might see a blue or bluish disk due to Rayleigh scattering (like Saturn and reflection nebulae, though only a few have enough regional surface brightness [e.g. Eskimo nebula]).

Seeing these colorful disks, of course, in the optical band would be very rare, if ever, due to the embryonic residual cloud blocking our view, I suppose. Yet within this there might be windows in time where some blue disks reside, until the gas is eventually depleted, or our neighbors become too distant.

When Lemaitre showed Einstein his expansion model that included Slipher’s redshifts and Hubbles’s distances, introducing the first stab at an expansion rate, Einstein remarked that the math was fine but the physics was “abominable“. :). So how’s my physics here? Are there experts in disk modeling that might have an interest in exploring this colorful idea that you know of off-hand?

iPad
 
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mmm

Mar 13, 2021
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Hi Joe,
Is there any data on other solar systems in the Milky Way that define the angle between their local ecliptic and the ecliptic of the Milky Way? In order for us to get maximum view of exoplanets transiting in front of their local sun, doesn't their solar system ecliptic need to be parallel to the Milky Way ecliptic? Our solar system ecliptic is at about 60 degrees to the Milky Way ecliptic so wouldn't only a tiny portion of the Milky Way be able to see any of our solar system planets transiting in front of the Sun? Are there other possible explanations for the transits we observe in other systems, such as sun spots?
thanks
 
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DrJoePesce

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What would happen if our solar system was 1 or 10 or 100 lightyears from a two black hole collision
that create these gravity waves we detect in our LIGOs ?
It would be fascinating to be so close to a blackhole (merging or not!), wouldn't it JLivingstonSG?

Certainly LIGO (NSF's Laser Interferometer Gravitational Wave Observatory: https://www.ligo.caltech.edu/), would have a much better signal from the event, but I think there is no issue from the gravitational waves at those distances. There might be problems from any electromagnetic radiation produced, in particular from the closer objects. It's still unclear whether such emission is possible, but it seems something has been detected from merging black holes, and if that includes a burst of gamma-rays and/or x-rays, then such "fireworks" wouldn't necessarily be good if the merger occurred nearby!
 
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DrJoePesce

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Why is the night sky dark?
Dr. Joe. A much cherished belief, especially of children, is that we should be able to find our way using just starlight. Unfortunately, when we actually do venture out on a moonless light, the reality is far different and the available starlight is not enough to light the way. The question is why? Even a very cursory mathematical calculation should show that, given that light travels forever and the sheer number of stars in the Universe, unless something gets in its way, that the night sky should be much brighter than it actually is. Light should accumulate and reinforce itself till the night sky should be as bright as day. Why is that not the case? The present theory that it is the expansion of the Universe that is shifting stars and galaxies away from us and that is why the sky is dark at night, is simply too theoretical and simply to far from our experienced reality. Wouldn’t a far more acceptable explanation for why the night sky is dark be that our notion of how light travels is wrong? Light does not travel forever, just like any wave, think of waves in water or sound waves, light travels until the original energy which created the light can no longer sustain its existence and then it fades away and returns into the medium from which it came. When one thinks of dark matter and the fact that it allows all electromagnetic radiation to travel through itself without offering the slightest resistance, one realizes that dark matter possesses exactly the same properties that the aether was once thought to possess.

What a profound question Jzz, and one on many levels. I love questions like this because there are so many things to talk about.

First of all: In extremely dark conditions, with the Milky Way directly overhead, you CAN read by the light of the stars. I've been fortunate to have done so many times (especially in the dark skies at our observatories in Chile). It is a spectacular, unforgettable, and moving experience.

But those dark skies necessary to do this are rapidly disappearing because of light pollution. Many (most?) of my astronomy students have never seen the Milky Way because of light pollution. How sad....

There are solutions to light pollution, and many are being enacted. See, for example, https://www.space.com/39787-light-pollution-problem-you-can-help.html

In other areas, what you ask is deeply insightful and is what's known as "Olbers' Paradox": Why is the night sky not bright (like the surface of a star)? But to ASK this question you have to make some assumptions: The universe is uniform and infinite. In such a universe (uniform and infinite), everywhere you look you will see a photon from a star (no matter how far away it is). In this case (ol' Heinreich Wilhelm Olbers would argue), the universe should be uniformly bright.

The simple answer is that the universe isn't uniform and infinite.

In such a universe, you CAN have sight lines without photons coming to your retina. That is, there are places we can look and not see light from any source. Since this is the case for quite a few "sight lines", the night sky is dark.
 

DrJoePesce

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What a profound question Jzz, and one on many levels. I love questions like this because there are so many things to talk about.

First of all: In extremely dark conditions, with the Milky Way directly overhead, you CAN read by the light of the stars. I've been fortunate to have done so many times (especially in the dark skies at our observatories in Chile). It is a spectacular, unforgettable, and moving experience.

But those dark skies necessary to do this are rapidly disappearing because of light pollution. Many (most?) of my astronomy students have never seen the Milky Way because of light pollution. How sad....

There are solutions to light pollution, and many are being enacted. See, for example, https://www.space.com/39787-light-pollution-problem-you-can-help.html

In other areas, what you ask is deeply insightful and is what's known as "Olbers' Paradox": Why is the night sky not bright (like the surface of a star)? But to ASK this question you have to make some assumptions: The universe is uniform and infinite. In such a universe (uniform and infinite), everywhere you look you will see a photon from a star (no matter how far away it is). In this case (ol' Heinreich Wilhelm Olbers would argue), the universe should be uniformly bright.

The simple answer is that the universe isn't uniform and infinite.

In such a universe, you CAN have sight lines without photons coming to your retina. That is, there are places we can look and not see light from any source. Since this is the case for quite a few "sight lines", the night sky is dark.
By the way, you say that a photon travels forever: If the photon doesn't interact with anything, it could travel forever. In reality, it will lose energy as the universe under it expands (i.e., redshift; and this is what the cosmic microwave background radiation is), and it's more likely an individual photon will not travel forever because it will be absorbed by gas, dust, other stars, retinas, etc.
 

DrJoePesce

Verified Expert
Mar 31, 2020
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I suspect I have already asked this in the past, but in case I haven’t... In my prior hunt for demonstrable evidence for the Sun’s true color - as seen in space properly attenuated - I have enjoyed learning about the physics of color that appears for many reasons (Rayleigh scattering, refraction, atomic emissions, etc.). For example, and related to my forthcoming question, the rich blue color that occasionally appears for most of Saturn’s northern hemisphere is a site to see. [This happens, apparently, due to a clearing effect that allows more Rayleigh scattering.]

Given the likelihood that the range of the number of nascent stars in the early solar neighborhood is about 1,000 to perhaps as many as 3,000 stars, per an earlier paper (IIRC), we would therefore likely have a couple of massive stars having formed, thanks to the application of the IMF (Initial Mass Function). As a result, a significant number of our new neighbors would also be extremely bright and would provide significant illumination upon our early solar accretion disk.

All of the above is to see if you know of anyone or paper that has addressed the possibility that such accretion disks would not look as artists color them but, like Saturn - blue to the human eye?

My suspect math indicates that a few bright neighbors could provide enough light to allow our photopic (color) vision to see color if it’s there. The disk being > 99% gas, and with the larger grains residing more in the middle, suggests to me we might see a blue or bluish disk due to Rayleigh scattering (like Saturn and reflection nebulae, though only a few have enough regional surface brightness [e.g. Eskimo nebula]).

Seeing these colorful disks, of course, in the optical band would be very rare, if ever, due to the embryonic residual cloud blocking our view, I suppose. Yet within this there might be windows in time where some blue disks reside, until the gas is eventually depleted, or our neighbors become too distant.

When Lemaitre showed Einstein his expansion model that included Slipher’s redshifts and Hubbles’s distances, introducing the first stab at an expansion rate, Einstein remarked that the math was fine but the physics was “abominable“. :). So how’s my physics here? Are there experts in disk modeling that might have an interest in exploring this colorful idea that you know of off-hand?

iPad
I have no doubt we could get all sorts of colors from protoplanetary disks (given the various elements composing them, grain size, etc. - as you noted). I'm not aware of anyone researching this per se, but our artist colleagues - always trying to depict astronomical objects with as high fidelity as possible - might be. It's not an issue that weighs much on the astronomer: we can take a spectrum and that tells us most of what we need.

As you know, the spectrometer is an instrument that allows us to break light into its consituent parts (like a prism does to white light, creating a rainbow of light). The spectum them tells us where the electromagnetic emission peaks in wavelength: a red star is going to have light from all visible-light wavelengths, but is brighter in the red than in the blue. And vice versa for a blue star. This information is useful: it tells us the color, and from that we infer surface temperature) and many other things. A spectrum can also tells what elements might be present in the astronomical object, to measure redshift (hence distance), etc.

So, it's more for aesthetic reasons that one would pursue what we would see with our eyes.

A couple of things: 1) yes, very bright, high mass stars would have been present during the early solar system to provide all sorts of high-energy photons (and even worse when they exploded as supernovae) and 2) the solar spectrum peaks around 5700A/570nm, meaning the Sun should have a slight greenish cast, though likely overwhelmed by brightness (not having been to space I can't answer this!).
 
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In reality, it will lose energy as the universe under it expands (i.e., redshift; and this is what the cosmic microwave background radiation is), and it's more likely an individual photon will not travel forever because it will be absorbed by gas, dust, other stars, retinas, etc.
Yes, and interestingly, without the redshift, we would indeed have a very bright universe with a BB distribution of ~ 3000K, sorta of a yellowish-orange I think. :)
 
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