Neptune is on the left, identifiable by the "Great Dark Spot" at its centre.
Above is a Voyager image in exaggerated colour. https://en.wikipedia.org/wiki/Great_Dark_Spot
Sunlight, being a mix of all different colours of light, is the truest example of “white light” that we know of.
It is a very dubious claim that the Sun is a green colour, but that our human eyes see it as white.
The green light peak in the Sun's spectrum certainly doesn’t mean that sunlight is green.
There are no stars anywhere in the Universe that look green to human eyes. However there are green planetary nebulae.
Planetary nebula IC 1295
The reason these appear green is because their light arises from a specific electron transition which occurs at a monochromatic wavelength: 500.7 nanometers - a green wavelength.
Discover more here: https://bigthink.com/starts-with-a-bang/what-color-is-the-sun/
Looks like a trip north of the border is out of the question until September
https://www.theguardian.com/uk-news...es-thriving-wet-scottish-summer-worse-to-come
https://www.theguardian.com/uk-news...es-thriving-wet-scottish-summer-worse-to-come
I've Heard the ‘green Sun’ thing before although the spectral emission peaks in the green band, as you note Galu, the light we see is mixed with other colours, so that’s why it’s white. Is there a specific element associated with the peak emission wavelength?
Failure to detect light from Planet Nine leads to the possibility that it is a black hole.
If so, it is only the size of a grapefruit and only 5 to 10 Earth masses.
If so, it is only the size of a grapefruit and only 5 to 10 Earth masses.
Wet weather has never stopped the kids from enjoying the Glasgow Fair holidays!
https://en.wikipedia.org/wiki/Glasgow_Fair
The peak emission occurs at about 500 nm (a green wavelength).
I don't believe this represents a monochromatic wavelength emitted by a specific element, but is associated with the average temperature of the Sun's surface which is just over 5500 K.
https://www.omnicalculator.com/physics/wiens-law
I understood planet 9 [P9] was explainable because all of the planetary orbits anre inclined wrt the sun’s polar axis. IIRC it’s 11 degrees for Pluto, but the others are 4-6 degrees which makes no sense. However, if there was a large body with a much greater orbital inclination, it would tip the other planetary orbits up from the expected horizontal plane, which is what we see today.
Midges may abound in Scotland, which does not surprise me, but the weird thing is we have almost no butterflies in England this year. I don't think I have seen one yet. Whatever is going on? 🙁
Maybe Planet 9 is responsible, not Global Warming? 🤣
I watched the TED Talk too. Very interesting.
The TNO (Er, Trans Neptunian Object) that killed Pluto, Eris and its moonlet Dysnomia:
https://en.wikipedia.org/wiki/Eris_(dwarf_planet)#
Artist's conception of Eris and its dark moon Dysnomia. No, I don't know which is supposed to be which either. 🤔
It's a tidge smaller than Pluto, but @Bonsai, MORE MASSIVE!
I was intrigued as to what "Argument of Perihelion" is. An orbital parameter, it seems.
https://www.sciencedirect.com/topics/physics-and-astronomy/argument-of-perihelion
Seems straightforward enough! In fact I'll take their word for it! 👍
Maybe Planet 9 is responsible, not Global Warming? 🤣
I watched the TED Talk too. Very interesting.
The TNO (Er, Trans Neptunian Object) that killed Pluto, Eris and its moonlet Dysnomia:
https://en.wikipedia.org/wiki/Eris_(dwarf_planet)#
Artist's conception of Eris and its dark moon Dysnomia. No, I don't know which is supposed to be which either. 🤔
It's a tidge smaller than Pluto, but @Bonsai, MORE MASSIVE!
I was intrigued as to what "Argument of Perihelion" is. An orbital parameter, it seems.
https://www.sciencedirect.com/topics/physics-and-astronomy/argument-of-perihelion
Seems straightforward enough! In fact I'll take their word for it! 👍
I was similarly intrigued.
However, since Mike Brown made no attempt to explain the term I knew it would be complicated! 😀
The "Argument of Perihelion" is actually an angle (ω) as is described here: https://astronomy.swin.edu.au/cosmos/A/Argument+Of+Perihelion
EDIT: I did a fair amount of editing, but got there eventually!
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I found this short explanatory video:
https://content.cld.iop.org/journal...tKTQueqanfj~NpUZQ__&Key-Pair-Id=KL1D8TIY3N7T8
The lunar caves featured in H G Wells' The First Men in the Moon actually do exist!
Profs at the University of Trento in Italy found the cave system by using radar to penetrate the opening of a pit on the Sea of Tranquility.
Perhaps someday we'll find the Selenites!
Sources:
https://www.seradata.com/h-g-wells-was-right-lunar-caves-do-exist/
https://www.bbc.co.uk/news/articles/ce784r9njz0o
Profs at the University of Trento in Italy found the cave system by using radar to penetrate the opening of a pit on the Sea of Tranquility.
Perhaps someday we'll find the Selenites!
Sources:
https://www.seradata.com/h-g-wells-was-right-lunar-caves-do-exist/
https://www.bbc.co.uk/news/articles/ce784r9njz0o
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I thought we were talking about Planet 9, @Galu. I know all about the Caves of the Moon, I am very well informed.
And used to enjoy a bit of potholing. Sumps, stalactites, carbide lamps and wetsuits and ladders and helmets... 😎
That Planet 9 video of yours was very slow to load! Weird.
Seems that what they were saying is there are a load of KBOs (Kuiper Belt Objects) that are coincidentally very elliptical and similarly aligned and take up to tens of thousands of years to orbit:
A 10 Earth mass object is the likely explanation. It will be very faint indeed due to distance and weakness of sunlight, which makes for a double inverse square faintness.
There is more... such an object will create even more highly inclined "Centaurs" at very odd angles to the ecliptic plane.
AFAIK, you need 6 orbital elements to describe the general elliptic orbit.
2 to define an ellipse. Eccentricity and semi-major axis.
2 to define the objects orbital plane relative to the ecliptic. Inclination and how twisted it is relatively.
2 to define the ecliptic plane itself. An argument angle, and either a time zero or an angular rate of precession called the true anomaly.
Making 6, just like x, y and z position and dx/dt, dy/dt and dz/dt momentum. I think conservation of angular momentum is happy to allow precession.
In practice, polar co-ordinates make more sense. This all takes some getting used to, but I think you want to use some sort of elliptical co-ordinates in the end to make it easier. And if there are symmetries like circular orbits you can get away with 5 elements.
https://en.wikipedia.org/wiki/Orbital_elements
All very interesting. We must wait and see where this pesky Planet 9 thing is lurking! It must be kind of opposite all the KBOs. Can't wait! 🙂
And used to enjoy a bit of potholing. Sumps, stalactites, carbide lamps and wetsuits and ladders and helmets... 😎
That Planet 9 video of yours was very slow to load! Weird.
Seems that what they were saying is there are a load of KBOs (Kuiper Belt Objects) that are coincidentally very elliptical and similarly aligned and take up to tens of thousands of years to orbit:
A 10 Earth mass object is the likely explanation. It will be very faint indeed due to distance and weakness of sunlight, which makes for a double inverse square faintness.
There is more... such an object will create even more highly inclined "Centaurs" at very odd angles to the ecliptic plane.
AFAIK, you need 6 orbital elements to describe the general elliptic orbit.
2 to define an ellipse. Eccentricity and semi-major axis.
2 to define the objects orbital plane relative to the ecliptic. Inclination and how twisted it is relatively.
2 to define the ecliptic plane itself. An argument angle, and either a time zero or an angular rate of precession called the true anomaly.
Making 6, just like x, y and z position and dx/dt, dy/dt and dz/dt momentum. I think conservation of angular momentum is happy to allow precession.
In practice, polar co-ordinates make more sense. This all takes some getting used to, but I think you want to use some sort of elliptical co-ordinates in the end to make it easier. And if there are symmetries like circular orbits you can get away with 5 elements.
https://en.wikipedia.org/wiki/Orbital_elements
All very interesting. We must wait and see where this pesky Planet 9 thing is lurking! It must be kind of opposite all the KBOs. Can't wait! 🙂
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I had looked at the above Wiki article when investigating the six Keplerian elements.
In that article the Argument of Perihelion is replaced by the general term Argument of Periapsis (both represented by the same angle ω).
The above diagram makes it all appear so easy peasy lemon squeezy, but it's not! 😀
In that article the Argument of Perihelion is replaced by the general term Argument of Periapsis (both represented by the same angle ω).
The above diagram makes it all appear so easy peasy lemon squeezy, but it's not! 😀
I've been puzzling over this all day! Your above diagram shows that two planes intercept in a straight line. Euclid would have known that.
But the perihelion (Helios = Sun) as the red vector can point anywhere. And the line of interception can point anywhere too.
I suppose in Astronomy we do everything relative to the Earth's orbit plane. The Ecliptic along which the planets and Moon roughly drift.
It's a terrible muddle really. I have decided henceforth to solely use Galactic Coordinates and Time:
https://en.wikipedia.org/wiki/Galactic_coordinate_system
You just need to know where Sagittarius A* and the Anticentre is, and use the Milky Way as your 0 degrees equator:
In the course of my research I found this picture from August 8, 2022 of Mars (and presumably faint Uranus) in Taurus, photographed from Earth.
Since Mars is in almost exactly the same place right now, we can confirm it orbits the Sun in approx. 1.9 years.
Orbital mechanics is really quite easy! 😀
But the perihelion (Helios = Sun) as the red vector can point anywhere. And the line of interception can point anywhere too.
I suppose in Astronomy we do everything relative to the Earth's orbit plane. The Ecliptic along which the planets and Moon roughly drift.
It's a terrible muddle really. I have decided henceforth to solely use Galactic Coordinates and Time:
https://en.wikipedia.org/wiki/Galactic_coordinate_system
You just need to know where Sagittarius A* and the Anticentre is, and use the Milky Way as your 0 degrees equator:
In the course of my research I found this picture from August 8, 2022 of Mars (and presumably faint Uranus) in Taurus, photographed from Earth.
Since Mars is in almost exactly the same place right now, we can confirm it orbits the Sun in approx. 1.9 years.
Orbital mechanics is really quite easy! 😀
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If Ecliptic Coordinates were good enough for Claudius Ptolemy, they're good enough for me! 🤓
Unlike the celestial equator, the plane of the ecliptic does not depend on the Earth’s axial precession.
This means that the plane of the ecliptic is fixed in space, providing a reliable reference for astronomers.
This coordinate business is getting worse! It seems that most of them rely on a plane and a centre and an orientation direction.
Usually you then choose one that makes the maths easy and wherein you know where you are and can thus navigate your spaceship.
Consider life for our intrepid heroes in the Firefly TV series (My Favourite Space Show), living in "The Verse", which I understand is a few tens of light years from "The Earth That Was":
I really don't know how Wash got them from A to B for more adventures every week in this confusing multi star/ multi planet system. Clearly White Sun centric.
However, Star Trek "Voyager" used Central Galactic coordinates but a similar squad of nine which allows a full arc of character development apparently.
You probably were as vague as I was where the Delta Quadrant was, apart from being 70,000 LY away, but now you know.
I did resist buying the Voyager boxed set, though I was a latecomer to the series. I really know little about The Maquis and why Kes got dumped from the series. But feel that life is too short for all that stuff.
My current obsession is to explore "coordinate free geometry". This seems the way forward. 😎
Usually you then choose one that makes the maths easy and wherein you know where you are and can thus navigate your spaceship.
Consider life for our intrepid heroes in the Firefly TV series (My Favourite Space Show), living in "The Verse", which I understand is a few tens of light years from "The Earth That Was":
I really don't know how Wash got them from A to B for more adventures every week in this confusing multi star/ multi planet system. Clearly White Sun centric.
However, Star Trek "Voyager" used Central Galactic coordinates but a similar squad of nine which allows a full arc of character development apparently.
You probably were as vague as I was where the Delta Quadrant was, apart from being 70,000 LY away, but now you know.
I did resist buying the Voyager boxed set, though I was a latecomer to the series. I really know little about The Maquis and why Kes got dumped from the series. But feel that life is too short for all that stuff.
My current obsession is to explore "coordinate free geometry". This seems the way forward. 😎