APOD: Zodiacal Road (2019 Jul 24)

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APOD: Zodiacal Road (2019 Jul 24)

Post by APOD Robot » Wed Jul 24, 2019 4:14 am

Image Zodiacal Road

Explanation: What's that strange light down the road? Dust orbiting the Sun. At certain times of the year, a band of sun-reflecting dust from the inner Solar System appears prominently just after sunset -- or just before sunrise -- and is called zodiacal light. Although the origin of this dust is still being researched, a leading hypothesis holds that zodiacal dust originates mostly from faint Jupiter-family comets and slowly spirals into the Sun. Recent analysis of dust emitted by Comet 67P, visited by ESA's robotic Rosetta spacecraft, bolster this hypothesis. Pictured when climbing a road up to Teide National Park in the Canary Islands of Spain, a bright triangle of zodiacal light appeared in the distance soon after sunset. Captured on June 21, the scene includes bright Regulus, alpha star of Leo, standing above center toward the left. The Beehive Star Cluster (M44) can be spotted below center, closer to the horizon and also immersed in the zodiacal glow.

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Re: APOD: Zodiacal Road (2019 Jul 24)

Post by Ann » Wed Jul 24, 2019 5:01 am

Queen, with Brian May second from left.
Freddy Mercury second from right.
Off topic, but did you know that Brian May, lead guitarist of the famous group Queen, is also an astrophysicist? And that he has studied the zodiacal light?
Wikipedia wrote:

Brian Harold May, CBE (born 19 July 1947) is an English musician, singer, songwriter and astrophysicist. He is the lead guitarist of the rock band Queen.
May studied physics and mathematics at Imperial College London, graduating with a BSc (Hons) degree and ARCS in physics with Upper Second-Class Honours. From 1970 to 1974, he studied for a PhD[1] degree at Imperial College, studying reflected light from interplanetary dust and the velocity of dust in the plane of the Solar System. When Queen started to have international success in 1974, he abandoned his doctoral studies, but co-authored two peer reviewed research papers,[137][138] which were based on his observations at the Teide Observatory in Tenerife.
In October 2006, May re-registered for his PhD at Imperial College and submitted his thesis in August 2007 (one year earlier than he estimated it would take to complete). As well as writing up the previous work he had done, May had to review the work on zodiacal dust undertaken during the intervening 33 years, which included the discovery of the zodiacal dust bands by NASA's IRAS satellite. After a viva voce, the revised thesis (titled A Survey of Radial Velocities in the Zodiacal Dust Cloud)[1] was approved in September 2007, some 37 years after it had been commenced.[139][140][141][22][142] He was able to submit his thesis only because of the minimal amount of research on the topic during the intervening years and has described the subject as one that became "trendy" again in the 2000s. His PhD investigated radial velocity using absorption spectroscopy and doppler spectroscopy of zodiacal light using a Fabry–Pérot interferometer based at the Teide Observatory in Tenerife. His research was initially supervised by Jim Ring,[2] Ken Reay[2] and in the latter stages by Michael Rowan-Robinson.[1] He graduated at the awards ceremony of Imperial College held in the Royal Albert Hall on 14 May 2008.
Enjoy this video about Brian May's thesis! :D

Click to play embedded YouTube video.

Ann
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Re: APOD: Zodiacal Road (2019 Jul 24)

Post by BDanielMayfield » Wed Jul 24, 2019 5:55 am

Ann, that's not off topic at all due to May's work as an astrophysicist on zodiacal dust. Thanks for sharing those Interesting facts. May has also worked (and played) for the New Horizon teem studying Ultima Thule.

I wonder, how heavy does a dust particle need to be for it to be drawn sunward rather than being swept away by solar wind and radiation?

Bruce
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Re: APOD: Zodiacal Road (2019 Jul 24)

Post by Boomer12k » Wed Jul 24, 2019 8:49 am

Is it visible to the naked eye? Because around sunset I think I saw something similar...

a patch of "lighter sky"...

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Re: APOD: Zodiacal Road (2019 Jul 24)

Post by De58te » Wed Jul 24, 2019 11:14 am

First thought is man those look like some rough seas off the Canary Islands. But there appears to be two sunsets. Why is the brighter sunset just off the left side of the road? I thought the sun sets on the horizon?

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Re: APOD: Zodiacal Road (2019 Jul 24)

Post by orin stepanek » Wed Jul 24, 2019 11:42 am

The Zodiacal light brightens up this wonderful picture! I wonder how many times we have seen this light and never paid it any attention? :roll:
Orin

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Re: APOD: Zodiacal Road (2019 Jul 24)

Post by BDanielMayfield » Wed Jul 24, 2019 12:18 pm

De58te wrote:
Wed Jul 24, 2019 11:14 am
First thought is man those look like some rough seas off the Canary Islands. But there appears to be two sunsets. Why is the brighter sunset just off the left side of the road? I thought the sun sets on the horizon?
What you're calling a "brighter sunset" off the road is from manmade lighting of human habitations. Note that this brightness is below the true horizon.
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Re: APOD: Zodiacal Road (2019 Jul 24)

Post by Tszabeau » Wed Jul 24, 2019 3:44 pm

Is it a disk of dust encircling the sun or a cloud of dust that circles the sun?

BTW - Sol, Terra, Luna, bowling ball is only 4 objects.

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Re: APOD: Zodiacal Road (2019 Jul 24)

Post by geckzilla » Wed Jul 24, 2019 3:58 pm

Tszabeau wrote:
Wed Jul 24, 2019 3:44 pm
Is it a disk of dust encircling the sun or a cloud of dust that circles the sun?

BTW - Sol, Terra, Luna, bowling ball is only 4 objects.
that's why there's also feather.
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Re: APOD: Zodiacal Road (2019 Jul 24)

Post by starsurfer » Wed Jul 24, 2019 4:19 pm

Ann wrote:
Wed Jul 24, 2019 5:01 am
Queen, with Brian May second from left.
Freddy Mercury second from right.
Off topic, but did you know that Brian May, lead guitarist of the famous group Queen, is also an astrophysicist? And that he has studied the zodiacal light?
Wikipedia wrote:

Brian Harold May, CBE (born 19 July 1947) is an English musician, singer, songwriter and astrophysicist. He is the lead guitarist of the rock band Queen.
May studied physics and mathematics at Imperial College London, graduating with a BSc (Hons) degree and ARCS in physics with Upper Second-Class Honours. From 1970 to 1974, he studied for a PhD[1] degree at Imperial College, studying reflected light from interplanetary dust and the velocity of dust in the plane of the Solar System. When Queen started to have international success in 1974, he abandoned his doctoral studies, but co-authored two peer reviewed research papers,[137][138] which were based on his observations at the Teide Observatory in Tenerife.
In October 2006, May re-registered for his PhD at Imperial College and submitted his thesis in August 2007 (one year earlier than he estimated it would take to complete). As well as writing up the previous work he had done, May had to review the work on zodiacal dust undertaken during the intervening 33 years, which included the discovery of the zodiacal dust bands by NASA's IRAS satellite. After a viva voce, the revised thesis (titled A Survey of Radial Velocities in the Zodiacal Dust Cloud)[1] was approved in September 2007, some 37 years after it had been commenced.[139][140][141][22][142] He was able to submit his thesis only because of the minimal amount of research on the topic during the intervening years and has described the subject as one that became "trendy" again in the 2000s. His PhD investigated radial velocity using absorption spectroscopy and doppler spectroscopy of zodiacal light using a Fabry–Pérot interferometer based at the Teide Observatory in Tenerife. His research was initially supervised by Jim Ring,[2] Ken Reay[2] and in the latter stages by Michael Rowan-Robinson.[1] He graduated at the awards ceremony of Imperial College held in the Royal Albert Hall on 14 May 2008.
Enjoy this video about Brian May's thesis! :D

Click to play embedded YouTube video.

Ann
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Re: APOD: Zodiacal Road (2019 Jul 24)

Post by neufer » Wed Jul 24, 2019 5:58 pm

Art Neuendorffer

Tszabeau

Re: APOD: Zodiacal Road (2019 Jul 24)

Post by Tszabeau » Wed Jul 24, 2019 5:59 pm

geckzilla wrote:
Wed Jul 24, 2019 3:58 pm
Tszabeau wrote:
Wed Jul 24, 2019 3:44 pm
Is it a disk of dust encircling the sun or a cloud of dust that circles the sun?

BTW - Sol, Terra, Luna, bowling ball is only 4 objects.
that's why there's also feather.
Doh! It’s the first one in the list too. I must be going blind. I double-checked and still overlooked it. Sigh.

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Re: APOD: Zodiacal Road (2019 Jul 24)

Post by Ann » Thu Jul 25, 2019 4:03 am

Boomer12k wrote:
Wed Jul 24, 2019 8:49 am
Is it visible to the naked eye? Because around sunset I think I saw something similar...

a patch of "lighter sky"...

:---[===] *
I didn't see that post, Boomer. Yes, the zodiacal light is visible to the naked eye, if you live in a dark place. But the zodiacal light is most easily visible in spring and fall, when the zodiacal light forms a steep angle with the horizon.

At least I think that Dr. Becky said so in the video about Brian May's thesis that I posted!

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Re: APOD: Zodiacal Road (2019 Jul 24)

Post by Apu » Thu Jul 25, 2019 4:41 pm

Didn't I see Richard Dreyfuss looking for mashed potatoes on that road?

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Re: APOD: Zodiacal Road (2019 Jul 24)

Post by Chris Peterson » Sat Jul 27, 2019 7:22 am

BDanielMayfield wrote:
Wed Jul 24, 2019 5:55 am
I wonder, how heavy does a dust particle need to be for it to be drawn sunward rather than being swept away by solar wind and radiation?
Particles smaller than about 1 um will be pushed outward by radiation pressure. Particles from there up to about 1 mm will experience Poynting–Robertson drag, and spiral in towards the Sun over thousands of years. Larger particles experience forces that depend upon their rotation, and can either be moved outward or inward.
Chris

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Re: APOD: Zodiacal Road (2019 Jul 24)

Post by BDanielMayfield » Sat Jul 27, 2019 11:21 am

Chris Peterson wrote:
Sat Jul 27, 2019 7:22 am
BDanielMayfield wrote:
Wed Jul 24, 2019 5:55 am
I wonder, how heavy does a dust particle need to be for it to be drawn sunward rather than being swept away by solar wind and radiation?
Particles smaller than about 1 um will be pushed outward by radiation pressure. Particles from there up to about 1 mm will experience Poynting–Robertson drag, and spiral in towards the Sun over thousands of years. Larger particles experience forces that depend upon their rotation, and can either be moved outward or inward.
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?

Bruce
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Re: APOD: Zodiacal Road (2019 Jul 24)

Post by Chris Peterson » Sat Jul 27, 2019 2:05 pm

BDanielMayfield wrote:
Sat Jul 27, 2019 11:21 am
Chris Peterson wrote:
Sat Jul 27, 2019 7:22 am
BDanielMayfield wrote:
Wed Jul 24, 2019 5:55 am
I wonder, how heavy does a dust particle need to be for it to be drawn sunward rather than being swept away by solar wind and radiation?
Particles smaller than about 1 um will be pushed outward by radiation pressure. Particles from there up to about 1 mm will experience Poynting–Robertson drag, and spiral in towards the Sun over thousands of years. Larger particles experience forces that depend upon their rotation, and can either be moved outward or inward.
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.
Chris

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Re: APOD: Zodiacal Road (2019 Jul 24)

Post 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.
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