Huh? Jupiter was absolutely brilliant in the sky during totality. It couldn't be missed.
Re: APOD: Total Eclipse and Comets (2024 Apr 17)
Posted: Wed Apr 17, 2024 3:10 pm
by florid_snow
You missed the "Of these" reference at the start of the sentence. I think the writer was just trying to point out that the comets and Mercury were not visible to the unaided eye. But yes, Jupiter was bright! It must be just out of frame in this image.
Re: APOD: Total Eclipse and Comets (2024 Apr 17)
Posted: Wed Apr 17, 2024 3:23 pm
by Chris Peterson
florid_snow wrote: ↑Wed Apr 17, 2024 3:10 pm
You missed the "Of these" reference at the start of the sentence. I think the writer was just trying to point out that the comets and Mercury were not visible to the unaided eye. But yes, Jupiter was bright! It must be just out of frame in this image.
Ah. Quite.
Re: APOD: Total Eclipse and Comets (2024 Apr 17)
Posted: Wed Apr 17, 2024 5:09 pm
by Cousin Ricky
I saw Jupiter (not shown) and Venus. The sky was too cloudy to see Mercury or 12/P, even through a binocular.
I did see solar prominences for the first time ever, though!
Re: APOD: Total Eclipse and Comets (2024 Apr 17)
Posted: Wed Apr 17, 2024 5:34 pm
by Badbubble
Sa Ji Tario wrote: ↑Wed Apr 17, 2024 2:50 pm
Where is the Pons-Brooks comet?
Sa Ji Tario wrote: ↑Wed Apr 17, 2024 2:50 pm
Where is the Pons-Brooks comet?
It is labled 12P in the image.
Yes. But I have yet to be able to find out why it's alternate designation is "12P". Is it the 12th periodic comet known perhaps?
Re: APOD: Total Eclipse and Comets (2024 Apr 17)
Posted: Wed Apr 17, 2024 7:30 pm
by AVAO
Eclectic Man wrote: ↑Wed Apr 17, 2024 8:01 am
Superb image, particularly the corona which extends further than in many other images.
That's right.
But you should always be aware of the spatial conditions.
It looks like the corona extends almost to Mercury.
In reality, Mercury's orbit is still quite far away...
Eclectic Man wrote: ↑Wed Apr 17, 2024 8:01 am
Superb image, particularly the corona which extends further than in many other images.
That's right.
But you should always be aware of the spatial conditions.
It looks like the corona extends almost to Mercury.
In reality, Mercury's orbit is still quite far away...
I couldn't find any definitive figures for the total extent of the Corona, which makes sense since it essentially just gradually rarifies the farther it gets from the Sun's surface, but this link says the Parker Solar Probe sampled the Corona at a distance of 8.2 million miles (13 million km):
This compares to the orbit of Mercury at an average distance of 34 million miles (55 million km). So, Mercury is still 4x farther away (from at least some rarified part of the Corona).
Eclectic Man wrote: ↑Wed Apr 17, 2024 8:01 am
Superb image, particularly the corona which extends further than in many other images.
That's right.
But you should always be aware of the spatial conditions.
It looks like the corona extends almost to Mercury.
In reality, Mercury's orbit is still quite far away...
I couldn't find any definitive figures for the total extent of the Corona, which makes sense since it essentially just gradually rarifies the farther it gets from the Sun's surface, but this link says the Parker Solar Probe sampled the Corona at a distance of 8.2 million miles (13 million km):
This compares to the orbit of Mercury at an average distance of 34 million miles (55 million km). So, Mercury is still 4x farther away (from at least some rarified part of the Corona).
Well, since the solar wind is the corona... all the planets are inside of it!
Re: APOD: Total Eclipse and Comets (2024 Apr 17)
Posted: Thu Apr 18, 2024 3:59 am
by shaileshs
I wonder what makes the comet get too close to the Sun ? I'd imagine gravity pull .. but then, how long it must have taken that comet to reach that stage (i mean how many times it must have made rounds around Sun and how many years it must have been doing it before finally getting too close and getting disintegrated) ? And, will the same thing happen to planets in our solar system too (will they get closer and closer over hundreds of millions of years and eventually get disintegrated OR before that happened Sun will reach 10B and will begin end of life phase by expanding and gulping planets till Mars) ?
Re: APOD: Total Eclipse and Comets (2024 Apr 17)
Posted: Thu Apr 18, 2024 4:55 am
by Ann
shaileshs wrote: ↑Thu Apr 18, 2024 3:59 am
I wonder what makes the comet get too close to the Sun ? I'd imagine gravity pull .. but then, how long it must have taken that comet to reach that stage (i mean how many times it must have made rounds around Sun and how many years it must have been doing it before finally getting too close and getting disintegrated) ? And, will the same thing happen to planets in our solar system too (will they get closer and closer over hundreds of millions of years and eventually get disintegrated OR before that happened Sun will reach 10B and will begin end of life phase by expanding and gulping planets till Mars) ?
I, the math expert, will explain.
Remember that comets are on very long orbits. They may encounter something on their very long orbits that will nudge their orbits a little bit. Their orbits are very (in many cases extremely) elongated. As you know (and as even I know), an ellipse has two focal points:
For a comet on an elongated orbit, nothing much is happening at its "far" (outer solar system) focal point, but when it comes back in, it sweeps past its other focal point, which is the Sun. Yikes! Not much nudging has to happen during one of its many orbits before the hapless comet takes the plunge!
Click to play embedded YouTube video.
However, not all comets pass very close to the Sun. Many (or most) don't.
As for the planets of the solar system, their orbits are in most cases close to circular. But the orbit of planet Mercury is less circular, and I think Mercury doesn't orbit in quite the same plane as the other planets. Since Mercury is also a lightweight planet that is the closest one to the Sun, and it is also being tugged at by the gravity of Venus and the Earth, its orbit is affected, so that it precesses. This means that the exact point of its orbit where it is closest to the Sun (perihelion) moves steadily "forward".
But unlike some hapless comets, we are not falling into the Sun. We may just be eaten by the Sun when it swells into red giant monster a couple of billion years from now.
shaileshs wrote: ↑Thu Apr 18, 2024 3:59 am
I wonder what makes the comet get too close to the Sun ? I'd imagine gravity pull .. but then, how long it must have taken that comet to reach that stage (i mean how many times it must have made rounds around Sun and how many years it must have been doing it before finally getting too close and getting disintegrated) ? And, will the same thing happen to planets in our solar system too (will they get closer and closer over hundreds of millions of years and eventually get disintegrated OR before that happened Sun will reach 10B and will begin end of life phase by expanding and gulping planets till Mars) ?
To add to Ann's explanation of gravitational perturbations: it does not need to take a long time. A comet may go around for thousands of years and never get close to the Sun, and then pass too near Jupiter and be deflected so it hits it (not common, but very much possible).
Orbital systems with just two bodies are stable. Their orbits will never change. But if you have three or more bodies, that stability is lost. Such systems will always change over time. Wait long enough and all the planets in the Solar System will be flung into interstellar space or into the Sun (except probably for Jupiter, which in the end would become a two-body system with the Sun). In theory even a two-body system will decay if you give it long enough, since bodies in orbit radiate gravitational radiation (like we pick up from merging black hole systems). But that energy loss is incredibly small, so the time scales are huge.
With comets, a few other things are going on. First, they are small and have non-uniform surfaces and shapes. So as they orbit, they are subject to forces from photons and even solar wind. That can slightly tweak their orbits. Second, as they near the Sun and expel gas and dust, their mass changes and they experience reaction forces. This also changes their orbit slightly. All of these effects are tiny, but they make it very difficult to accurately predict where a comet is going to be in hundreds or thousands of years, as these small effects, along with gravitational perturbations from Jupiter and Saturn, accumulate.
shaileshs wrote: ↑Thu Apr 18, 2024 3:59 am
I wonder what makes the comet get too close to the Sun ? I'd imagine gravity pull .. but then, how long it must have taken that comet to reach that stage (i mean how many times it must have made rounds around Sun and how many years it must have been doing it before finally getting too close and getting disintegrated) ? And, will the same thing happen to planets in our solar system too (will they get closer and closer over hundreds of millions of years and eventually get disintegrated OR before that happened Sun will reach 10B and will begin end of life phase by expanding and gulping planets till Mars) ?
To add to Ann's explanation of gravitational perturbations: it does not need to take a long time. A comet may go around for thousands of years and never get close to the Sun, and then pass too near Jupiter and be deflected so it hits it (not common, but very much possible).
Orbital systems with just two bodies are stable. Their orbits will never change. But if you have three or more bodies, that stability is lost. Such systems will always change over time. Wait long enough and all the planets in the Solar System will be flung into interstellar space or into the Sun (except probably for Jupiter, which in the end would become a two-body system with the Sun). In theory even a two-body system will decay if you give it long enough, since bodies in orbit radiate gravitational radiation (like we pick up from merging black hole systems). But that energy loss is incredibly small, so the time scales are huge.
With comets, a few other things are going on. First, they are small and have non-uniform surfaces and shapes. So as they orbit, they are subject to forces from photons and even solar wind. That can slightly tweak their orbits. Second, as they near the Sun and expel gas and dust, their mass changes and they experience reaction forces. This also changes their orbit slightly. All of these effects are tiny, but they make it very difficult to accurately predict where a comet is going to be in hundreds or thousands of years, as these small effects, along with gravitational perturbations from Jupiter and Saturn, accumulate.
But I suppose even if there are only two bodies in a system, like, say, the Sun and Jupiter, the Sun may - and will - change mass over time through its evolution along the Hertzsprung-Russell diagram due to changes in its nuclear fusion processes. So I'd think that could also eventually perturb Jupiter's orbit?
shaileshs wrote: ↑Thu Apr 18, 2024 3:59 am
I wonder what makes the comet get too close to the Sun ? I'd imagine gravity pull .. but then, how long it must have taken that comet to reach that stage (i mean how many times it must have made rounds around Sun and how many years it must have been doing it before finally getting too close and getting disintegrated) ? And, will the same thing happen to planets in our solar system too (will they get closer and closer over hundreds of millions of years and eventually get disintegrated OR before that happened Sun will reach 10B and will begin end of life phase by expanding and gulping planets till Mars) ?
To add to Ann's explanation of gravitational perturbations: it does not need to take a long time. A comet may go around for thousands of years and never get close to the Sun, and then pass too near Jupiter and be deflected so it hits it (not common, but very much possible).
Orbital systems with just two bodies are stable. Their orbits will never change. But if you have three or more bodies, that stability is lost. Such systems will always change over time. Wait long enough and all the planets in the Solar System will be flung into interstellar space or into the Sun (except probably for Jupiter, which in the end would become a two-body system with the Sun). In theory even a two-body system will decay if you give it long enough, since bodies in orbit radiate gravitational radiation (like we pick up from merging black hole systems). But that energy loss is incredibly small, so the time scales are huge.
With comets, a few other things are going on. First, they are small and have non-uniform surfaces and shapes. So as they orbit, they are subject to forces from photons and even solar wind. That can slightly tweak their orbits. Second, as they near the Sun and expel gas and dust, their mass changes and they experience reaction forces. This also changes their orbit slightly. All of these effects are tiny, but they make it very difficult to accurately predict where a comet is going to be in hundreds or thousands of years, as these small effects, along with gravitational perturbations from Jupiter and Saturn, accumulate.
But I suppose even if there are only two bodies in a system, like, say, the Sun and Jupiter, the Sun may - and will - change mass over time through its evolution along the Hertzsprung-Russell diagram due to changes in its nuclear fusion processes. So I'd think that could also eventually perturb Jupiter's orbit?
Yeah, because a true two-body system consists of point masses. In the real world, the two bodies aren't points or perfect, homogeneous spheres. So there are other forces involved (like tidal ones), and as you note, masses can change due to lost material. In practice, though, I don't think the changes the Sun or Jupiter will go through would ever result in Jupiter being ejected. Just having its orbital parameters tweaked.
Re: APOD: Total Eclipse and Comets (2024 Apr 17)
Posted: Thu Apr 18, 2024 4:54 pm
by shaileshs
Thank you Ann and Chris. As always, you help me understand things a bit better.
Re: APOD: Total Eclipse and Comets (2024 Apr 17)
Posted: Thu Apr 18, 2024 5:38 pm
by Fred the Cat
In a two-dimensional image, the corona extends perpendicularly but what of the part that is directed toward or away from us? The actual corona extends in all directions during a “total eclipse” image of the moon. This may entail a SOHO-like orbiter above the sun’s poles following the Cluster mission unless Parker fulfills that objective.
Fred the Cat wrote: ↑Thu Apr 18, 2024 5:38 pm
In a two-dimensional image, the corona extends perpendicularly but what of the part that is directed toward or away from us? The actual corona extends in all directions during a “total eclipse” image of the moon. This may entail a SOHO-like orbiter above the sun’s poles following the Cluster mission unless Parker fulfills that objective.
Are you suggesting that the Corona might be markedly different in the portions of it that we can't currently study well (that is, those portions that extend in directions other than in the 2-D radial view we usually see during eclipses)?
EDIT: come to think of it, we ARE currently viewing the Corona through sight lines that extend through almost all the Corona since the Moon is only blocking a very narrow 0.5° cone! Right?
Chris Peterson wrote: ↑Thu Apr 18, 2024 2:16 pm
To add to Ann's explanation of gravitational perturbations: it does not need to take a long time. A comet may go around for thousands of years and never get close to the Sun, and then pass too near Jupiter and be deflected so it hits it (not common, but very much possible).
Orbital systems with just two bodies are stable. Their orbits will never change. But if you have three or more bodies, that stability is lost. Such systems will always change over time. Wait long enough and all the planets in the Solar System will be flung into interstellar space or into the Sun (except probably for Jupiter, which in the end would become a two-body system with the Sun). In theory even a two-body system will decay if you give it long enough, since bodies in orbit radiate gravitational radiation (like we pick up from merging black hole systems). But that energy loss is incredibly small, so the time scales are huge.
With comets, a few other things are going on. First, they are small and have non-uniform surfaces and shapes. So as they orbit, they are subject to forces from photons and even solar wind. That can slightly tweak their orbits. Second, as they near the Sun and expel gas and dust, their mass changes and they experience reaction forces. This also changes their orbit slightly. All of these effects are tiny, but they make it very difficult to accurately predict where a comet is going to be in hundreds or thousands of years, as these small effects, along with gravitational perturbations from Jupiter and Saturn, accumulate.
But I suppose even if there are only two bodies in a system, like, say, the Sun and Jupiter, the Sun may - and will - change mass over time through its evolution along the Hertzsprung-Russell diagram due to changes in its nuclear fusion processes. So I'd think that could also eventually perturb Jupiter's orbit?
Yeah, because a true two-body system consists of point masses. In the real world, the two bodies aren't points or perfect, homogeneous spheres. So there are other forces involved (like tidal ones), and as you note, masses can change due to lost material. In practice, though, I don't think the changes the Sun or Jupiter will go through would ever result in Jupiter being ejected. Just having its orbital parameters tweaked.
And when the Sun expands in a few billion years, might that be enough to affect the outer planet orbits much?
Fred the Cat wrote: ↑Thu Apr 18, 2024 5:38 pm
In a two-dimensional image, the corona extends perpendicularly but what of the part that is directed toward or away from us? The actual corona extends in all directions during a “total eclipse” image of the moon. This may entail a SOHO-like orbiter above the sun’s poles following the Cluster mission unless Parker fulfills that objective.
Are you suggesting that the Corona might be markedly different in the portions of it that we can't currently study well (that is, those portions that extend in directions other than in the 2-D radial view we usually see during eclipses)?
But I suppose even if there are only two bodies in a system, like, say, the Sun and Jupiter, the Sun may - and will - change mass over time through its evolution along the Hertzsprung-Russell diagram due to changes in its nuclear fusion processes. So I'd think that could also eventually perturb Jupiter's orbit?
Yeah, because a true two-body system consists of point masses. In the real world, the two bodies aren't points or perfect, homogeneous spheres. So there are other forces involved (like tidal ones), and as you note, masses can change due to lost material. In practice, though, I don't think the changes the Sun or Jupiter will go through would ever result in Jupiter being ejected. Just having its orbital parameters tweaked.
And when the Sun expands in a few billion years, might that be enough to affect the outer planet orbits much?
The simple expansion of the Sun should really have no significant impact on those orbits at all. It effectively appears as a point mass to them.
Yeah, because a true two-body system consists of point masses. In the real world, the two bodies aren't points or perfect, homogeneous spheres. So there are other forces involved (like tidal ones), and as you note, masses can change due to lost material. In practice, though, I don't think the changes the Sun or Jupiter will go through would ever result in Jupiter being ejected. Just having its orbital parameters tweaked.
And when the Sun expands in a few billion years, might that be enough to affect the outer planet orbits much?
The simple expansion of the Sun should really have no significant impact on those orbits at all. It effectively appears as a point mass to them.
Fred the Cat wrote: ↑Thu Apr 18, 2024 5:38 pm
In a two-dimensional image, the corona extends perpendicularly but what of the part that is directed toward or away from us? The actual corona extends in all directions during a “total eclipse” image of the moon. This may entail a SOHO-like orbiter above the sun’s poles following the Cluster mission unless Parker fulfills that objective.
Are you suggesting that the Corona might be markedly different in the portions of it that we can't currently study well (that is, those portions that extend in directions other than in the 2-D radial view we usually see during eclipses)?
Did you notice my edit of my post since your reply? (I'm never sure if that causes people to get a separate notice of a change or not.)
This was what I had added:
EDIT: come to think of it, we ARE currently viewing the Corona through sight lines that extend through almost all the Corona since the Moon is only blocking a very narrow 0.5° cone! Right?
Total Eclipse and Comets
