by BDanielMayfield » Sat Jul 27, 2019 6:34 pm
Chris Peterson wrote: ↑Sat Jul 27, 2019 2:05 pm
BDanielMayfield wrote: ↑Sat Jul 27, 2019 11:21 am
Thanks Chris. So, rather than mass, surface area, rotation and distance from the sun determines which way a particular particle drifts. Over time a sorting process would therefore tend to select a set of particles that would experience net zero forces over the period of a full orbit and so would remain in stable orbits indefinitely?
I realize that this isn't a simple question due to the variability of solar wind and comet conditions, but over very long time spans since conditions can be averaged out, is the zodiacal dust building up, or is it thinning out?
There is no balance. Other forces come into play, as well, such as electric charge and solar wind and thermal effects. Also, the particles collide which breaks them down. All interplanetary dust is short-lived- probably nothing is older than a few million years (probably more like tens of thousands for zodiacal dust). Interplanetary dust is constantly being lost, and constantly being renewed. The total amount at any one time probably isn't constant, either, as there are things like asteroid collisions that may inject a lot of new material at random times. Also, the number of Jupiter-family comets (the source for most zodiacal dust) varies over time.
Thanks again. That makes sense. And reading the link on Jupiter-family comets I see that they are relatively short-lived as well. From that link:
Although the orbits of Jupiter-family comets are contained within or do not extend much beyond the orbit of Jupiter, it is thought that they originate in the Kuiper Belt, a collection of rock-ice bodies located just beyond the orbit of Neptune. Collisions between Kuiper Belt objects break off small chunks of ice and rock, which can then be gravitationally perturbed by Neptune into highly elliptical orbits around the Sun. As they approach Jupiter, the orbits of these small bodies may be perturbed further, resulting in a tighter ellipse and a shorter orbital period.
This origin for Jupiter-family comets is supported by the observation that they all have relatively low orbital inclinations (the average around 18 deg. to the plane of the ecliptic), and most orbit in the same direction as the planets. This is in contrast to the Halley-type comets and long-period comets whose orbital inclinations can be very high, and which are thought to originate in the spherical Oort cloud.
There are currently over 400 Jupiter-family comets known, most of which are extremely faint. This is due to the rapid depletion of their volatiles through multiple trips to the inner Solar System, brought about by their short orbital periods.
So if not for the presence of both the Kuiper Belt and the planet Neptune the zodiacal light would be much less than it currently is.
[quote="Chris Peterson" post_id=294041 time=1564236306 user_id=117706]
[quote=BDanielMayfield post_id=294038 time=1564226514 user_id=139536]
Thanks Chris. So, rather than mass, surface area, rotation and distance from the sun determines which way a particular particle drifts. Over time a sorting process would therefore tend to select a set of particles that would experience net zero forces over the period of a full orbit and so would remain in stable orbits indefinitely?
I realize that this isn't a simple question due to the variability of solar wind and comet conditions, but over very long time spans since conditions can be averaged out, is the zodiacal dust building up, or is it thinning out?
[/quote]
There is no balance. Other forces come into play, as well, such as electric charge and solar wind and thermal effects. Also, the particles collide which breaks them down. All interplanetary dust is short-lived- probably nothing is older than a few million years (probably more like tens of thousands for zodiacal dust). Interplanetary dust is constantly being lost, and constantly being renewed. The total amount at any one time probably isn't constant, either, as there are things like asteroid collisions that may inject a lot of new material at random times. Also, the number of Jupiter-family comets (the source for most zodiacal dust) varies over time.
[/quote]
Thanks again. That makes sense. And reading the link on Jupiter-family comets I see that they are relatively short-lived as well. From that link:
[quote]Although the orbits of Jupiter-family comets are contained within or do not extend much beyond the orbit of Jupiter, it is thought that they originate in the Kuiper Belt, a collection of rock-ice bodies located just beyond the orbit of Neptune. Collisions between Kuiper Belt objects break off small chunks of ice and rock, which can then be gravitationally perturbed by Neptune into highly elliptical orbits around the Sun. As they approach Jupiter, the orbits of these small bodies may be perturbed further, resulting in a tighter ellipse and a shorter orbital period.
This origin for Jupiter-family comets is supported by the observation that they all have relatively low orbital inclinations (the average around 18 deg. to the plane of the ecliptic), and most orbit in the same direction as the planets. This is in contrast to the Halley-type comets and long-period comets whose orbital inclinations can be very high, and which are thought to originate in the spherical Oort cloud.
There are currently over 400 Jupiter-family comets known, most of which are extremely faint. This is due to the rapid depletion of their volatiles through multiple trips to the inner Solar System, brought about by their short orbital periods.[/quote]
So if not for the presence of both the Kuiper Belt and the planet Neptune the zodiacal light would be much less than it currently is.