Starship Asterisk*

by **Nitpicker** » Thu May 25, 2017 12:55 am

Of course, I don't want to understate things, either. The ~1% difference in the rotation rates of the equatorial and temperate latitudes, is still enough to create a velocity differential of ~360 km/hr (224 mph) in the cloud tops of Jupiter. This is more than enough to muss up one's hair.

by **Nitpicker** » Wed May 24, 2017 10:28 pm

Thayer, the imagery of the poles is stretched when reprojected, in keeping with what is possible when observing from Earth.

I wasn't attempting to nitpick anything in my responses. Nor to criticize in a negative way. I was merely providing some additional commentary on this fantastic APOD video.

Peter, whether or not "illusion" is an appropriate word is largely a question of semantics. It is certainly an effect. The way the flyover simulation is presented, makes it appear that only one or two Jovian days have elapsed in terms of Jupiter's rotation with respect to the Sun. Concurrently, the clouds evolve over a period of ~240 Jovian days. Both have been sped up considerably compared with the duration of the simulation, but by different amounts. This may not be obvious to everyone on first viewing. Had the flyover been presented without a night side, these two different rates would not be apparent, but it might have lost some aesthetic appeal and it would no longer represent the approach path of Juno. I do like the way it has been presented, but also felt it needed some additional commentary on the stroboscopic effect, at least for those of us on the Starship. You have explained the process thoroughly elsewhere. Love your work.

by **MarkBour** » Wed May 24, 2017 5:19 pm

Nitpicker wrote:In reality, the equatorial clouds on Jupiter rotate faster than the rest of the clouds. This is typically referred to as System I (~878 degrees per Earth-day) and System II (~870 degrees per Earth-day). So, over the ~100 Earth-day period shown in the video, the equatorial band fully rotates roughly two extra times, say 242 times, vs 240. . . .

Thanks, Nitpicker. That clears it up for me.

by **Peter R** » Wed May 24, 2017 2:30 pm

thayer wrote:I am amazed that you are all nitpicking about the rotation velocity or frame flash rate. This video was assembled from imagery taken on Earth, so how did they get pictures of the poles? Obviously they did some fancy editing combining in imagery from Juno. You are missing the forest for the trees people!

Peter R wrote:
One true magic while producing these animations was to be able to fly above the poles of a planet 630 million kilometers away from Earth and thus only photographed from the side.

/*Peter R

Thayer, no images from Juno were used. I only used ground based telescopic images taken by amateurs from around the world.
Please refer to my original video on Youtube https://www.youtube.com/watch?v=YZc1Y662jtk or the article I wrote for The Planetary Society some weeks ago for some additional explanations on the polar projections http://www.planetary.org/blogs/guest-bl ... piter.html

/*Peter R

by **Ann** » Wed May 24, 2017 2:25 pm

florid_snow wrote:
Ann wrote:
florid_snow wrote:This is beautiful. I feel the wonder of the planets, the hope in scientific pursuit, and the love in a community effort. Thank you Peter Rosen and all the contributing observers from all over Earth. Thank you APOD team.
Thank you for posting a beautiful and inspiring comment, which was even more lovely before you edited it.

Ann
The original just had an extra couple of sentences, I was worried of being too topical and emotional, I didn't want to color other experiences with how the news of the bombing in Manchester affected me. The original below. Thank you for your kind words Ann. And thanks again Peter Rosen!

This is beautiful. Tears in my eyes tonight, less justified than many on this planet I'm sure. But then I came here and shed a few more. I feel the wonder of the planets, the hope in scientific pursuit, and the love in a community effort. Thank you Peter Rosen and all the contributing observers from all over Earth. Thank you APOD team

Thanks for posting your full post again.

Like you, I think that the universe can provide some sort of comfort and consolation in times of sorrow. At the very least, it provides perspective.

Ann

by **Peter R** » Wed May 24, 2017 2:22 pm

MarkBour wrote:
florid_snow wrote:
MarkBour wrote: ... which gives the impression that the central equatorial band of clouds is orbiting at an incredible speed.

But it is delightful and educational to watch, nonetheless!
The impression? But it is in fact rotating so fast!
In this animation, the equatorial-band clouds appear to circle Jupiter at least 15 times as fast as the Great Red Spot, but I believe this is a "stroboscopic illusion".

The purpose of doing this animation was twofold: to be aesthetically appealing and scientifically correct. The frames in the animation are composed only of real ground based telescopic images so the movements of the cloud belts relative each others are absolutely correct. If the Equatorial Zone (EZ) seems to rusch like a rapid, it is precisely what it does. Remember that the speed has been increased 2 million times. It is 1 frame per earthday compared to the real time flow of 25 frames per second. Therefore I am not too fond of the expression "stroboscopic illusion" as there is no illusion, just the fact that we are not used to seeing the clouds evolve at this higher speed. The term "stroboscopic" can only be used when discussing the rotation speed of the planet itself around its axis which I can control at will, like the pilot of a spaceship, the former I cannot.

/*Peter R

by **thayer** » Wed May 24, 2017 2:02 pm

I am amazed that you are all nitpicking about the rotation velocity or frame flash rate. This video was assembled from imagery taken on Earth, so how did they get pictures of the poles? Obviously they did some fancy editing combining in imagery from Juno. You are missing the forest for the trees people!

Peter R wrote:
One true magic while producing these animations was to be able to fly above the poles of a planet 630 million kilometers away from Earth and thus only photographed from the side.

/*Peter R

by **Nitpicker** » Wed May 24, 2017 10:42 am

And ... Oops ... It is called the equatorial zone, not band. One day I'll stop mixing them up.

by **MarkBour** » Wed May 24, 2017 6:47 am

florid_snow wrote:
MarkBour wrote:
Peter R wrote: ... There are in fact 2 animations at play simultaneously.
The clouds evolve accelerated about 2 million times their normal speed independently of the rotation of the planet.
/*Peter R
... which gives the impression that the central equatorial band of clouds is orbiting at an incredible speed.

But it is delightful and educational to watch, nonetheless!
The impression? But it is in fact rotating so fast!

In this animation, the equatorial-band clouds appear to circle Jupiter at least 15 times as fast as the Great Red Spot, but I believe this is a "stroboscopic illusion".

by **Nitpicker** » Wed May 24, 2017 6:40 am

florid_snow wrote:
MarkBour wrote:
Peter R wrote: ... There are in fact 2 animations at play simultaneously.
The clouds evolve accelerated about 2 million times their normal speed independently of the rotation of the planet.
/*Peter R
... which gives the impression that the central equatorial band of clouds is orbiting at an incredible speed.

But it is delightful and educational to watch, nonetheless!
The impression? But it is in fact rotating so fast!

In reality, the equatorial clouds on Jupiter rotate faster than the rest of the clouds. This is typically referred to as System I (~878 degrees per Earth-day) and System II (~870 degrees per Earth-day). So, over the ~100 Earth-day period shown in the video, the equatorial band fully rotates roughly two extra times, say 242 times, vs 240. When System II is held stationary, or nearly stationary, as in the video, you see the different rates quite clearly and you also see the more subtle variations in speed within System II. Neither system can be said to truly rotate at a constant speed -- they are clouds, after all -- but the systems offer at least some, um, system of measurement.

There is also a System III, which is the "official" one based on measurements of the rotation of Jupiter's magnetic field, which is unobservable to most amateurs (and possibly its core, which is thus far unobservable to everyone). System III is close in rotation rate to System II (slightly faster I think). But all these cloud patterns, including the GRS, drift in longitude over time, in relation to all three systems.

To an observer rotating with System II or III, the equatorial band would appear to rotate about 3 degrees per Jovian day. Not that fast by comparison, perhaps.

by **florid_snow** » Wed May 24, 2017 5:19 am

MarkBour wrote:
Peter R wrote: ... There are in fact 2 animations at play simultaneously.
The clouds evolve accelerated about 2 million times their normal speed independently of the rotation of the planet.
/*Peter R
... which gives the impression that the central equatorial band of clouds is orbiting at an incredible speed.

But it is delightful and educational to watch, nonetheless!

The impression? But it is in fact rotating so fast!

by **florid_snow** » Wed May 24, 2017 5:17 am

Ann wrote:
florid_snow wrote:This is beautiful. I feel the wonder of the planets, the hope in scientific pursuit, and the love in a community effort. Thank you Peter Rosen and all the contributing observers from all over Earth. Thank you APOD team.
Thank you for posting a beautiful and inspiring comment, which was even more lovely before you edited it.

Ann

The original just had an extra couple of sentences, I was worried of being too topical and emotional, I didn't want to color other experiences with how the news of the bombing in Manchester affected me. The original below. Thank you for your kind words Ann. And thanks again Peter Rosen!

This is beautiful. Tears in my eyes tonight, less justified than many on this planet I'm sure. But then I came here and shed a few more. I feel the wonder of the planets, the hope in scientific pursuit, and the love in a community effort. Thank you Peter Rosen and all the contributing observers from all over Earth. Thank you APOD team

by **MarkBour** » Tue May 23, 2017 8:29 pm

Peter R wrote: ... There are in fact 2 animations at play simultaneously.
The clouds evolve accelerated about 2 million times their normal speed independently of the rotation of the planet.
/*Peter R

... which gives the impression that the central equatorial band of clouds is orbiting at an incredible speed.

But it is delightful and educational to watch, nonetheless!

by **Peter R** » Tue May 23, 2017 6:44 pm

Thank you all for your comments.

florid_snow wrote:This is beautiful. I feel the wonder of the planets, the hope in scientific pursuit, and the love in a community effort. Thank you Peter Rosen and all the contributing observers from all over Earth. Thank you APOD team.

Thank you florid_snow. I haven't read the unedited version that Ann is referring to, but what you wrote made me wake up with a warm smile on my face.

Nitpicker wrote:This is a fantastic project and a huge effort. I love the cylindrical and polar projection animations shown in the video in the first link.

The simulation of the Juno flyby is perhaps a little fanciful. It is very much a "stroboscopic" time-lapse, as in reality, Jupiter would have rotated ~250 times over this ~100 Earth-day time period -- too fast to see any of the changes in Jupiter's cloud patterns. Maybe I am being influenced by my experience of tuning old car engines with a strobe light, but I feel a strange urge to tweak the timing a bit, so as to keep the Great Red Spot stationary, relative to the Sun angle.

Nitpicker, you are absolutely right about the "stroboscopic" effect, and the stationary Great Red Spot is what occurs when you take one image every 9h56m corresponding exactly to one revolution of Jupiter. That is what is shown in the famous Voyager approach movie from 1979 and that I replicated in our "Voyager 3" video 3 years ago. But if you increase or decrease the timing by some minutes, you will get a slow prograde or retrograde rotation of the planet itself while the cloud belts will evolve independently in exactly the same way.There are in fact 2 animations at play simultaneously.
The clouds evolve accelerated about 2 million times their normal speed independently of the rotation of the planet.

One true magic while producing these animations was to be able to fly above the poles of a planet 630 million kilometers away from Earth and thus only photographed from the side.

/*Peter R

by **Ann** » Tue May 23, 2017 4:29 pm

florid_snow wrote:This is beautiful. I feel the wonder of the planets, the hope in scientific pursuit, and the love in a community effort. Thank you Peter Rosen and all the contributing observers from all over Earth. Thank you APOD team.

Thank you for posting a beautiful and inspiring comment, which was even more lovely before you edited it.

Ann

by **Chris Peterson** » Tue May 23, 2017 1:41 pm

desertengineer wrote:Interesting factoid...

If you were to travel towards Jupiter very near the speed of light, and shift the color spectrum down from blue to visible, this is how you would see the journey. Heavily exaggerated because it's a few light hours away. If it were light days away where a Newtonian journey would take years, you would see the time dilation per above.

An observer in orbit around Jupiter, correcting the shifts would see the opposite?

Just some back-of-the-envelope calculations: it looks like we're observing about 15 hours of time (1.5 Jupiter rotations). Assuming we start our journey from Earth, and travel 4 AU, means a speed of about 10,000 km/s. So, about 0.03c, which is essentially non-relativistic.

In reality, the simulation appears to start much closer to Jupiter than the Earth (Jupiter's apparent size only increases by about one order of magnitude), so this simulation actually models something that we might see with an actual probe traveling at a currently attainable speed.

by **desertengineer** » Tue May 23, 2017 1:23 pm

Interesting factoid...

If you were to travel towards Jupiter very near the speed of light, and shift the color spectrum down from blue to visible, this is how you would see the journey. Heavily exaggerated because it's a few light hours away. If it were light days away where a Newtonian journey would take years, you would see the time dilation per above.

An observer in orbit around Jupiter, correcting the shifts would see the opposite?

by **Chris Peterson** » Tue May 23, 2017 1:05 pm

APOD Robot wrote:Image taking began in 2014 December and lasted just over three months. The resulting fictitious approach sequence...

I think "simulated" would be a far better description than "fictitious".

by **heehaw** » Tue May 23, 2017 11:29 am

I agree with Nitpicker! But I am also reminded of Phil Morrison's call to imagine viewing the rotation of our Galaxy over a billion years. It would rotate 360 degrees five times or so over that timespan. But! You imagined it incorrectly! You forgot that every couple of hundred years a supernova would have been going off! So your imagined galaxy should actually look like a fireworks pinwheel!

by **RedFishBlueFish** » Tue May 23, 2017 9:56 am

A product of society at its best.

Wonderful.

Thanks to those who did the scientific and technical work necessary to obtain the images, to those who created this clip and thanks to to all of us US tax-payers who funded such horizon expanding exploration.

by **Nitpicker** » Tue May 23, 2017 5:57 am

This is a fantastic project and a huge effort. I love the cylindrical and polar projection animations shown in the video in the first link.

The simulation of the Juno flyby is perhaps a little fanciful. It is very much a "stroboscopic" time-lapse, as in reality, Jupiter would have rotated ~250 times over this ~100 Earth-day time period -- too fast to see any of the changes in Jupiter's cloud patterns. Maybe I am being influenced by my experience of tuning old car engines with a strobe light, but I feel a strange urge to tweak the timing a bit, so as to keep the Great Red Spot stationary, relative to the Sun angle.

by **florid_snow** » Tue May 23, 2017 4:48 am

This is beautiful. I feel the wonder of the planets, the hope in scientific pursuit, and the love in a community effort. Thank you Peter Rosen and all the contributing observers from all over Earth. Thank you APOD team.

by **APOD Robot** » Tue May 23, 2017 4:08 am

Approaching Jupiter

Explanation: What would it look like to approach Jupiter? To help answer this, a team of 91 amateur astrophotographers took over 1,000 pictures of Jupiter from the Earth with the resulting images aligned and digitally merged into the featured time-lapse video. Image taking began in 2014 December and lasted just over three months. The resulting fictitious approach sequence has similarities to what was seen by NASA's robotic Juno spacecraft as it first approached the Jovian world last July. The video begins with Jupiter appearing as a small orb near the image center. As Jupiter nears from below, the planet looms ever larger while the rotation of its cloud bands becomes apparent. Jupiter's shrinking Great Red Spot rotates into view twice, at times showing unusual activity. Many white ovals are visible moving around the giant planet. The video ends as the imaginary spacecraft passes over Jupiter's North Pole.

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