Starship Asterisk*

by **Beyond** » Thu Nov 29, 2012 6:50 pm

Ann wrote:I still think too much learning might shrivel your brain.

D'OH!

by **Ann** » Thu Nov 29, 2012 5:30 pm

bystander wrote:
Ann wrote:By the way, bystander, how do you write "70" (seventy) as a binary number, in base 2?
1000110

Click to play embedded YouTube video.

I still think too much learning might shrivel your brain.

Ann

by **PhilT** » Thu Nov 29, 2012 2:55 pm

No one has mentioned that the 17 days to opposition also means that we are not viewing the shadow with the sun directly behind us but rather from a considerable bit to the side - 17 days means something like 36 degrees to the side (~360 * 17/365/2).

By the way, no comments in reply to my original cooling effect question yet !!!!!!

BR/P
PS Yes, I know Jupiter is moving too, I'm just illustrating that it's no surprise that the shadow is offset.

by **neufer** » Thu Nov 29, 2012 2:22 pm

JohnD wrote:
neufer wrote:I do know differently, John. Differently is a friend of mine.

If Io was lying on the surface of Jupiter its shadow would be directly under it
as viewed from Earth (~ 3.6º off the Sun-Jupiter axis).
http://space.jpl.nasa.gov/cgi-bin/wspac ... 1&showac=1

If Io was just one Jupiter radius above the surface of Jupiter
its shadow would be ~ 3.6º east longitude on Jupiter as viewed from Earth (~ 3.6º off the Sun-Jupiter axis).

Since Io is ~ 5 Jupiter radii above the surface of Jupiter
its shadow is ~ 18º east longitude on Jupiter as viewed from Earth (~ 3.6º off the Sun-Jupiter axis).
Thank you neufer! I now have a different perspective of your view.
But not the relevance of your link, which shows the Inner System from Jupiter.
Can that view be adapted to show, even animate, the Earth view of Jupiter?
JOhn

The perspective was to show the ~ 3.6º angle between the Earth & the Sun as seen from Jupiter.

One can also approximate the angle by remembering that
the Earth moves ~ 1º daily in it's orbit about the Sun
and this was 16 days before opposition so it is ~ 16º.

From Jupiter at 5.2 AU that Earth orbital angle appears to be only ~ 16º/(5.2-1) = ~ 3.8º .

[Since Jupiter is orbiting as well once every 12 years
(such that Earth passes Jupiter only 11 times in 12 years)
this reduces to ~ 3.8º x 11/12 = 3.5º.]

The (shadowless) view of Jupiter from Earth shows the position on Io, itself, on Nov. 17 00:00UT:
http://space.jpl.nasa.gov/cgi-bin/wspac ... 1&showac=1

The view of Jupiter from the Sun indicates the position on Io's shadow on Nov. 17 00:00UT:
http://space.jpl.nasa.gov/cgi-bin/wspac ... 1&showac=1

by **DavidLeodis** » Thu Nov 29, 2012 12:16 pm

The posts about the name IO looking like 10 (ten) got me wondering, so just for fun:-

10 (decimal) is A (hexadecimal base 16).
10 (hexadecimal) is 16 (decimal).
10 (hexadecimal colours) is a shade of blue.
10 (decimal) is 12 (octal base 8).
10 (octal) is 8 (decimal).

It's a shame that IO is not blue!

by **JohnD** » Thu Nov 29, 2012 9:03 am

neufer wrote:I do know differently, John. Differently is a friend of mine.

If Io was lying on the surface of Jupiter its shadow would be directly under it
as viewed from Earth (~ 3.6º off the Sun-Jupiter axis).
http://space.jpl.nasa.gov/cgi-bin/wspac ... 1&showac=1

If Io was just one Jupiter radius above the surface of Jupiter
its shadow would be ~ 3.6º east longitude on Jupiter as viewed from Earth (~ 3.6º off the Sun-Jupiter axis).

Since Io is ~ 5 Jupiter radii above the surface of Jupiter
its shadow is ~ 18º east longitude on Jupiter as viewed from Earth (~ 3.6º off the Sun-Jupiter axis).

Thank you neufer! I now have a different perspective of your view.
But not the relevance of your link, which shows the Inner System from Jupiter.
Can that view be adapted to show, even animate, the Earth view of Jupiter?
JOhn

by **bystander** » Thu Nov 29, 2012 8:15 am

Ann wrote:By the way, bystander, how do you write "70" (seventy) as a binary number, in base 2?

1000110

And what is "base 2 70" in ordinary base 10?

There is no '7' in binary, only '1' and '0'.

by **Beyond** » Thu Nov 29, 2012 7:09 am

Ann wrote:
bystander wrote:
Beyond wrote:Well... he did 'write' it, so according to what you said, the joke worked. And of course ten means ten, so why did you say what you said, bystander?
10 in binary is not ten, it's two. The joke makes no sense if you use the word ten.

"There are 10 ten kinds of people in the world: Those who understand binary and those who don't!"
Ummm. I feel like the "0" part of the "10" here. I remember a little - make that a microscopic tiny amount - of the binary stuff we were taught in school. And that was back in the seventies, long before ordinary people knew what a computer was.

By the way, bystander, how do you write "70" (seventy) as a binary number, in base 2? And what is "base 2 70" in ordinary base 10?

Ann

I'm in the same "0" boat as ann, but w-a-y at the back, hanging off the stern by my fingernails.

by **Ann** » Thu Nov 29, 2012 7:02 am

bystander wrote:
Beyond wrote:Well... he did 'write' it, so according to what you said, the joke worked. And of course ten means ten, so why did you say what you said, bystander?
10 in binary is not ten, it's two. The joke makes no sense if you use the word ten.

"There are 10 ten kinds of people in the world: Those who understand binary and those who don't!"

Ummm. I feel like the "0" part of the "10" here. I remember a little - make that a microscopic tiny amount - of the binary stuff we were taught in school. And that was back in the seventies, long before ordinary people knew what a computer was.

By the way, bystander, how do you write "70" (seventy) as a binary number, in base 2? And what is "base 2 70" in ordinary base 10?

Ann

by **bystander** » Thu Nov 29, 2012 5:36 am

Beyond wrote:Well... he did 'write' it, so according to what you said, the joke worked. And of course ten means ten, so why did you say what you said, bystander?

10 in binary is not ten, it's two. The joke makes no sense if you use the word ten.

"There are 10 ten kinds of people in the world: Those who understand binary and those who don't!"

by **Beyond** » Thu Nov 29, 2012 4:23 am

bystander wrote:
flash wrote:Reminds me of an old quip:
"There are ten kinds of people in the world: Those who understand binary and those who don't!"
That joke only works if you write it
"There are 10 kinds of people ..."
Ten is a word that means, well, ten, not two.

Well... he did 'write' it, so according to what you said, the joke worked. And of course ten means ten, so why did you say what you said, bystander?

by **bystander** » Thu Nov 29, 2012 2:14 am

flash wrote:Reminds me of an old quip:
"There are ten kinds of people in the world: Those who understand binary and those who don't!"

That joke only works if you write it
"There are 10 kinds of people ..."
Ten is a word that means, well, ten, not two.

by **flash** » Thu Nov 29, 2012 1:29 am

Ann wrote:
owlice wrote: I cannot help but think of this little bit of verse when seeing an image of Jupiter and Io: http://www.baltastro.org/AstroPoetry.html#JupiterAndTen

I agree. "Jupiter and Ten" sounds considerably more frustratingly fascinating than "Jupiter and Io" (Jupiter and IO?)

Ann

Reminds me of an old quip:
"There are 10 (not ten) kinds of people in the world: Those who understand binary and those who don't!"

by **Anthony Barreiro** » Thu Nov 29, 2012 12:17 am

Boomer12k wrote:"Dance of the Planets", round and round ad infinitum.

I've been waiting for Chris to remind us that the planets will not orbit the Sun for an infinite length of time, explaining the relevant orbital mechanics and the effects of the evolution of the Sun itself ... .

by **Boomer12k** » Wed Nov 28, 2012 10:38 pm

"Dance of the Planets", round and round ad infinitum.

:---[===] *

by **neufer** » Wed Nov 28, 2012 9:44 pm

bystander wrote:
neufer wrote:
JohnD wrote:
Unless you know differently.
I do know differently, John. Differently is a friend of mine.
I thought you were differently. There's another like you?

I'm definitely diffidently not differently.

by **bystander** » Wed Nov 28, 2012 8:20 pm

neufer wrote:
JohnD wrote:Unless you know differently.
I do know differently, John. Differently is a friend of mine.

I thought you were differently. There's another like you?

by **Anthony Barreiro** » Wed Nov 28, 2012 6:29 pm

Regarding the displacement between Io and Io's shadow on Jupiter's cloud tops, you also need to remember that Io and Jupiter's other moons orbit Jupiter's equator. While Jupiter's equator is only inclined three degrees relative to the plane of it's orbit around the Sun, this angle is enough to affect what we see from here on Earth as we look at Jupiter from along the ecliptic plane. In addition to the east-west displacement (and shadow eclipses) seen before and after opposition, we will also see the moons casting shadows to the south of the equator during Jupiter's northern hemisphere summer (as currently) and to the north during Jupiter's northern hemisphere winter in six years. At Jupiter's equinoxes the shadows will pass right over the equator and a moon will pass directly over its shadow at mid-transit. Jupiter's next equinox will happen in 2015.

Near Jupiter's northern winter solstice, as currently, Ganymede passes high behind Jupiter's northern limb and low in front of the southern limb. More distant Callisto passes above and below the disk of Jupiter as seen from Earth.

And regarding whether Jupiter is approaching us or we are approaching Jupiter, I believe the answer is "yes."

This a lovely series of images, by the way, thank you Alessandro!

Anybody with a telescope of any size and a clear sky should be observing Jupiter and his moons these nights. While you may not see the level of detail in Alessandro's pictures, you will see the cloud bands, and you can watch the moons in their graceful orbital dance and strive to understand what Galileo figured out using a crude one-inch refractor.

by **neufer** » Wed Nov 28, 2012 6:02 pm

mtilley wrote:
I'm curious about the temporal spacing of these pictures, given Jupiter's rotation rate and IO's orbital period.

Can anyone clarify?

~Every half hour on average?

http://space.jpl.nasa.gov/cgi-bin/wspac ... 1&showac=1

http://space.jpl.nasa.gov/cgi-bin/wspac ... 1&showac=1

by **mtilley** » Wed Nov 28, 2012 5:52 pm

I'm curious about the temporal spacing of these pictures, given Jupiter's rotation rate and IO's orbital period.

Can anyone clarify?

by **neufer** » Wed Nov 28, 2012 5:49 pm

JohnD wrote:
neufer, I can't square your answer with geometry. The distance of Io from Jupiter is irrelevant.

At the orbit of Jupiter, the Sun's rays are as near to parallel as dammit.
So the distance Io moves daily in its orbit is the same as the distance moved on the 'surface' of Jupiter, increased as the shadow moves away from directly under the Sun, and decreased as the shadow moves from the limb of Jupiter towards its centre, by the Tangent of the angle of the sun above the horizon.

Unless you know differently.

I do know differently, John. Differently is a friend of mine.

If Io was lying on the surface of Jupiter its shadow would be directly under it
as viewed from Earth (~ 3.6º off the Sun-Jupiter axis).
http://space.jpl.nasa.gov/cgi-bin/wspac ... 1&showac=1

If Io was just one Jupiter radius above the surface of Jupiter
its shadow would be ~ 3.6º east longitude on Jupiter as viewed from Earth (~ 3.6º off the Sun-Jupiter axis).

Since Io is ~ 5 Jupiter radii above the surface of Jupiter
its shadow is ~ 18º east longitude on Jupiter as viewed from Earth (~ 3.6º off the Sun-Jupiter axis).

by **JohnD** » Wed Nov 28, 2012 5:23 pm

neufer,
I can't square your answer with geometry. The distance of Io from Jupiter is irrelevant.

At the orbit of Jupiter, the Sun's rays are as near to parallel as dammit.
So the distance Io moves daily in its orbit is the same as the distance moved on the 'surface' of Jupiter, increased as the shadow moves away from directly under the Sun, and decreased as the shadow moves from the limb of Jupiter towards its centre, by the Tangent of the angle of the sun above the horizon.

That difference would not be visible from Earth at opposition, when we are looking along the Sun's rays, although it should be if we could see Jupiter 'from the side', with an obvious terminator. Do we ever see it that way, except from Galileo?

I'll gladly accept your point about the pictures being taken some time before true opposition. If the angle of the Sun was so great in relation to the angle of view from Earth that Io's shadow is so displaced, should we not see the terminator at the edge of Jupiter's disc, peeping around it by a similar amount?
John

by **FloridaMike** » Wed Nov 28, 2012 4:54 pm

neufer wrote:
1) The picture was taken over a fortnight before opposition.

2) Io orbits almost 5 Jupiter radii above Jupiter's surface
. thereby exaggerating the solar surface shadow displacement (as viewed from Earth) by a factor of ~5.

Ahhh, I was thinking of the angular change in Jupiter's position over a "fortnight" and neglecting the angular change of the earth. Thanks!

by **Ann** » Wed Nov 28, 2012 4:13 pm

owlice wrote: I cannot help but think of this little bit of verse when seeing an image of Jupiter and Io: http://www.baltastro.org/AstroPoetry.html#JupiterAndTen

I agree. "Jupiter and Ten" sounds considerably more frustratingly fascinating than "Jupiter and Io" (Jupiter and IO?)

Ann

by **Gary again** » Wed Nov 28, 2012 4:04 pm

Gary E. Johnson wrote:If Jupiter and Sol are at opposition in Earth's sky, then the sun's rays passing earth go directly to Jupiter. Why is it that we can see the shadow of Io on Jupiter's surface? Shouldn't that shadow be directly behind the moon?

Guess I should read all posts before posting -- a good expanation was already provided. Thanks and cheers!

Starship Asterisk*

APOD: Jupiter and Io (2012 Nov 28)

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