The Boring Sky (Sun)

[Cargo]

The Hubble Space Telescope circles Earth at an altitude of 353 miles (568 kilometers), but its orbit decays over time due to atmospheric drag. Therefore, it is inside Earth's atmosphere. Actually the Thermosphere if I recall correctly.

We must also be aware that hubble visible light images have exposure times measured in hours or even days.

[Brent72]

Thanks for that good info Cargo and Mo.
Still getting my head around it, but I think we’re on the same page. Light is only visible when it’s interacting with matter - either in our atmosphere or in space. And the interaction causes changes in direction.

I understand that in the standard interpretation of stars, quasars, galaxies etc; if they have very high redshift, they are deemed to be at huge distances from earth and consequently they must be very bright. However if it turns out that these objects are not so distant, (because parallax measurements are wrong), then wouldn’t this provide further evidence that the redshift is not actually cosmological but intrinsic?

[Maol]

The Hubble Space Telescope circles Earth at an altitude of 353 miles (568 kilometers), but its orbit decays over time due to atmospheric drag. Therefore, it is inside Earth's atmosphere. Actually the Thermosphere if I recall correctly.

We must also be aware that hubble visible light images have exposure times measured in hours or even days.

More to read than this and a larger image, follow the link.

https://sohowww.nascom.nasa.gov/hotshots/2019_02_20/



The outermost part of our planet's atmosphere extends well beyond the lunar orbit -- almost twice the distance to the Moon.

A recent discovery based on observations by the ESA/NASA Solar and Heliospheric Observatory, SOHO, shows that the gaseous layer that wraps around Earth reaches up to 630,000 km away, or 50 times the diameter of our planet. "The Moon flies through Earth's atmosphere," says Igor Baliukin of Russia's Space Research Institute, lead author of the paper presenting the results. "We were not aware of it until we dusted off observations made over two decades ago by the SOHO spacecraft."

Where our atmosphere merges into outer space, there is a cloud of hydrogen atoms called the geocorona. One of the spacecraft instruments, SWAN, used its sensitive sensors to trace the hydrogen signature and precisely detect how far the very outskirts of the geocorona are. These observations could be done only at certain times of the year, when the Earth and its geocorona came into view for SWAN.

For planets with hydrogen in their exospheres, water vapour is often seen closer to their surface. That is the case for Earth, Mars and Venus. "This is especially interesting when looking for planets with potential reservoirs of water beyond our Solar System," explains Jean-Loup Bertaux, co-author and former principal investigator of SWAN. The first telescope on the Moon, placed by Apollo 16 astronauts in 1972, captured an evocative image of the geocorona surrounding Earth and glowing brightly in ultraviolet light. "At that time, the astronauts on the lunar surface did not know that they were actually embedded in the outskirts of the geocorona," says Jean-Loup.

Cloud of hydrogen
The Sun interacts with hydrogen atoms through a particular wavelength of ultraviolet light called Lyman-alpha, which the atoms can both absorb and emit. Since this type of light is absorbed by Earth's atmosphere, it can only be observed from space. Thanks to its hydrogen absorption cell, the SWAN instrument could selectively measure the Lyman-alpha light from the geocorona and discard hydrogen atoms further out in interplanetary space. The new study revealed that sunlight compresses hydrogen atoms in the geocorona on Earth's dayside, and also produces a region of enhanced density on the night side. The denser dayside region of hydrogen is still rather sparse, with just 70 atoms per cubic centimeter at 60,000 kilometers above Earth's surface, and about 0.2 atoms at the Moon's distance.

"On Earth we would call it vacuum, so this extra source of hydrogen is not significant enough to facilitate space exploration," says Igor. The good news is that these particles do not pose any threat for space travelers on future crewed missions orbiting the Moon. "There is also ultraviolet radiation associated to the geocorona, as the hydrogen atoms scatter sunlight in all directions, but the impact on astronauts in lunar orbit would be negligible compared to the main source of radiation -- the Sun," says Jean-Loup Bertaux.

[Brent72]

Great post Maol.
Cheers.

[moses]

Rather than consider quasars think about Sirius. If Sirius is orders of magnitude closer to us that mainstream tells us, and it's unusually large brightness is one indicator of this, then a big possibility is that a few thousand years ago Sirius would have been very close indeed to the Solar System and thus have been extremely bright in the sky.

The major evidence for this is the Dogon and their fascination with Sirius and knowledge of Sirius B which is not visible today but probably would have been if Sirius was very close to the Solar System.

Cheers,
Mo

[Brent72]

Even if you use the mainstream numbers for recessional velocity of 80km/s, Sirius would have to have been about 10 trillion km closer 4000 years ago. (Or about one light year).

[moses]

The radial velocity of the centre of mass of the Sirius system relies upon the mass of Sirius A and Sirius B and probably their distance apart. The Lehmann-Filhes formula for radial velocity uses the Sun - Sirius distance. So that gives a value perhaps 100 times greater than using 1/100 of the Sun - Sirius distance. Consequently it is doubtful we can say the Sirius system is moving away or towards us. Time will tell as there is a 50 year orbit.

Cheers,
Mo

[GaryN]

If there is no such thing as visible light from the sun to scatter in the atmosphere and cause the blue sky then what else could make it so? Here is my model:


https://www.britannica.com/science/Rydberg-constant

O2 produces those spectral lines when subject to ionising UV radiation, so where does the UV come from?

https://4570book.info/amazing-cliparts/ ... lipart.htm

The Lyman Alpha UV emissions are shown in the partial shell covering the daylight side of the Earth, so what produces the UV emissions? Neon maybe?

What may energise the neon? EUV perhaps?

Moon-based EUV imaging of the Earth’s Plasmasphere:Model simulations
https://agupubs.onlinelibrary.wiley.com ... 13JA018962

And above it all, the gamma radiation. All planets with or without atmospheres emit gamma rays, and moons too, including our own, which is the only reason I believe that the Moon (or anything else) is visible at all from Earth.

The Earth - in Gamma-Rays!
https://imagine.gsfc.nasa.gov/science/f ... earth.html
The gamma radiation is produced by cosmic rays of solar origin.

The blue sky from excited O2 is the main thing, above that there may well be many emission/absorption events occurring in the many layers that form above the Earth so my model is just a suggestion, not a fully researched fact, but the mechanisms to produce the blue light without scattering of visible light are certainly there.
And the red spectral line of O2? Less of it, and water in the atmosphere likely absorbing much of it, while blue light is only very weakly absorbed.

[GaryN]

I watched this youtube video by the Smithsonian National Air and Space Museum about Moon Photography and then posted a question: "What I am unable to determine is the actual near or far side daytime surface illumination levels, lux or foot-candles. You guys would seem likely to know the answer to that question!" When I visit the page again now I do not see my comment unless I log in and then do a page refresh so was wondering if anyone else could see my comment, logged in or not.
https://www.youtube.com/watch?v=hvygi0jwy6w&lis=

I also E-Mailed a similar question to the contact person at NASA Ames Research Center and got a quick reply. "I am sorry that I can't provide specific exposure details." That is from the Solar System Exploration Research Virtual Institute. Can't because they do not know or will not tell?
https://sservi.nasa.gov/overview/

[Cargo]

Damn right they can't. Or the whole charade would be exposed.
I see zero public comments on that youtube page.

[GaryN]

Damn right they can't. Or the whole charade would be exposed.
I see zero public comments on that youtube page.

Thanks for taking a look Cargo. My comment does show up now if I am logged in or not, but a comment by another user has vanished. Maybe the Gootube software is just flaky but I suspect it is 'opinion steering' in action.
Someone they haven't censored, though bits seem to be missing out of this vid, is Chris Hadfield. Here he is telling us how black space is when you look away from Earth during an EVA. He has done this in a few videos but never actually says he can not see stars as he just never mentions them at all. Surely after waxing eloquent about the beauty and splendour of the Earth below he would have something to say about the stars? Or are they just too boring to even worth while mentioning?
https://youtu.be/t93UCj1hzu8?t=252

[GaryN]

Electric Asteroid Breaks the Rules | Space News
https://www.thunderbolts.info/wp/2020/0 ... pace-news/

The asteroid 6478 Gault was seen to change colours from red to blue. This is an observation from Earth of course, so the colours are being produced in Earths atmosphere by interaction of the x-ray or EUV emissions from the asteroid. No photographs of naked eye visible comets showing colour have ever been taken from space except from the ISS cupola, which of course is looking through Earths atmosphere. It was tried with comet Bennet on April 13 1970 by the Apollo 13 crew and of course saw nothing at all.

[moses]

Lately the news is that our Sun is way quieter than other Sun-like stars. About 12 times quieter. Now if those stars were 3 to 4 times closer than they think then those Sun-like stars would be just as quiet as our Sun. And all that is required is light to bend a bit coming towards the Sun.
Cheers,
Mo

[GaryN]

"And all that is required is light to bend a bit coming towards the Sun."
I have often wondered if the Van Allen Belts have an effect on the view of the (supposed) stars that we see from Earth. Of course they won't show us a view of the stars from outside of the belts, even though they have no problems putting satellites into 22,000 mile high orbits which are in the outer region of the belts. They have lots of cameras looking at the Earth from high orbit, none looking away from Earth. Pity.
I am still hoping Elon Musk may put up a space telescope, or better still, why not put up a few small, visible light space telescopes and create an array that would give a telescope with an effective diameter far greater than Hubbles? On the other hand though, he probably already knows there is nothing to be seen out there at visible wavelengths. Maybe Joe Rogan could put the question to him next time Musk is a guest?

[Cargo]

Of interest I happened along some information about OSIRIS-REx visible wavelength cameras, there are 3 of them. During calibration phase in situ the CCD's had exposure times from .4ms to 1.4ms for the earth and moon shots. The pictures show the effort to check and manage ever pixel, and maybe how difficult the task is, taking a picture. There are also star-field calibration shots that measured around 10s to take. But I have not found pictures of those tests yet.