APOD: Jupiter and Io (2012 Nov 28)

APOD Robot · Post by **APOD Robot** » Wed Nov 28, 2012 5:06 am

Jupiter and Io

Explanation: On December 3 (UT), Jupiter, the solar system's largest planet, will be at opposition, opposite the Sun in planet Earth's sky, shining brightly and rising as the Sun sets. That configuration results in Jupiter's almost annual closest approach to planet Earth. So, near opposition the gas giant offers earthbound telescopes stunning views of its stormy, banded atmosphere and large Galilean moons. For example, this sharp series was recorded on the night of November 16/17 from the island of Sardinia near Dolianova, Italy. North is up in the images that show off Jupiter's famous Great Red Spot, and planet girdling dark belts and light zones. Also seen in transit is Jupiter's volcanic moon Io, its round, dark shadow tracking across the Jovian cloud tops as the sequence progresses left to right.

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A.A. Verveen · Post by **A.A. Verveen** » Wed Nov 28, 2012 8:52 am

Nice squinted-eye "3D pictures" of Jupiter, and and also of Jupiter and Io!

PhilT · Post by **PhilT** » Wed Nov 28, 2012 9:41 am

Hi,
I've experienced an eclipse once here on Earth and there was a noticeable temperature drop (surprise, surprise

).

Could the shadowing effect of IO affect the storms on Jupiter and explain why we see bands of storms ?

Just a thought/Phil

5jdw28 · Post by **5jdw28** » Wed Nov 28, 2012 11:03 am

The Earth, with its shorter orbit, approaches Jupiter each year, NOT the other way around!!!
Try for some ACCURACY, PLEASE.
It is annoying to constantly find errors of fact, grammar, and spelling at this site.
And you actually have TWO editors who aren't doing their jobs!

owlice · Post by **owlice** » Wed Nov 28, 2012 11:08 am

If the site annoys you, perhaps you ought not to be looking at it.

~~~~~~~~~~~~~~~~~~~

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

JohnD · Post by **JohnD** » Wed Nov 28, 2012 11:55 am

If Jupiter is at opposition, and the images of it confirm that - no shadowed area on the gas surface, why is the shadow of Io so displaced to the right?
Even when Io approaches the centre of Jupiter's disc, the shadow is significantly displaced, when I would expect it to almost coincide.

John

Markus Schwarz · Post by **Markus Schwarz** » Wed Nov 28, 2012 11:57 am

5jdw28 wrote:The Earth, with its shorter orbit, approaches Jupiter each year, NOT the other way around!!!
Try for some ACCURACY, PLEASE.

Dear 5djw28,
since English is not my native language, I looked up the meaning of approach at Merriam-Webster. I find the following two examples helpful:
- The cat approached the baby cautiously.
- Ease off the gas pedal to slow down as the bend in the road approaches.
In the first example the cat actively closes the distance to the baby, and the situation is viewed by a third observer. In the second example, the situation is viewed from inside a vehicle, say a car. Clearly, the bend in the road is not approaching the car actively. An observer on the side of the road would say that the car approaches the bend.
IMHO, the situation is the same for Earth and Jupiter. You take the position of an outside observer, who sits at the center of gravity of the solar system. Earthlings that they are, the APOD editors seem to take the second point of view. From my linguistic understandings, both are correct statements.
From a physics point of view, keep in mind that you can solve the equations of motion for the planets in any coordinate system you like. In practice, they are most easily solved if you take the center of gravity as the origin. But besides mathematical complexity, nothing prevents you from solving them taking Earth as your origin.

soulfly66 · Post by **soulfly66** » Wed Nov 28, 2012 1:28 pm

Hi i'm Wolfgang F. from Austria greetings to all here on this site.
What a splendid page Astronomy picture of the Day Thank you sooooooo much enjoy it every Day!!!!

ber.droid · Post by **ber.droid** » Wed Nov 28, 2012 1:37 pm

JohnD wrote:If Jupiter is at opposition, and the images of it confirm that - no shadowed area on the gas surface, why is the shadow of Io so displaced to the right?
Even when Io approaches the centre of Jupiter's disc, the shadow is significantly displaced, when I would expect it to almost coincide.

I was immediately wondering at this, too!

Ber

FloridaMike · Post by **FloridaMike** » Wed Nov 28, 2012 2:18 pm

ber.droid wrote:
JohnD wrote:If Jupiter is at opposition, and the images of it confirm that - no shadowed area on the gas surface, why is the shadow of Io so displaced to the right?
Even when Io approaches the centre of Jupiter's disc, the shadow is significantly displaced, when I would expect it to almost coincide.
I was immediately wondering at this, too!

Ber

I "third" this question.

neufer · Post by **neufer** » Wed Nov 28, 2012 2:20 pm

ber.droid wrote:
JohnD wrote:
If Jupiter is at opposition, and the images of it confirm that -
no shadowed area on the gas surface, why is the shadow of Io so displaced to the right?

Even when Io approaches the centre of Jupiter's disc, the shadow is significantly displaced, when I would expect it to almost coincide.
I was immediately wondering at this, too!

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.

APOD Robot wrote: Jupiter and Io

On December 3 (UT), Jupiter will be at opposition,
this sharp series was recorded on the night of November 16/17

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

moonstruck · Post by **moonstruck** » Wed Nov 28, 2012 2:34 pm

hi io

neufer · Post by **neufer** » Wed Nov 28, 2012 2:52 pm

Click to play embedded YouTube video.

moonstruck wrote:
hi io

Chris Peterson wrote:
I know of nothing about the Universe that precludes teleportation, but the Universe seems quite adamant about its restriction on conveying information faster than light. So this thought experiment becomes just another variation on "what if we could travel faster than light", replete with the same paradoxes and causality variations. Amusing, but with no basis in reality.

Gary E. Johnson · Post by **Gary E. Johnson** » Wed Nov 28, 2012 4:00 pm

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?

Gary again · Post 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!

Ann · Post 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

FloridaMike · Post 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!

JohnD · Post 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

neufer · Post 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).

mtilley · Post 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?

neufer · Post 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

Anthony Barreiro · Post 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.

bystander · Post 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?

neufer · Post 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.

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

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

:---[===] *

Starship Asterisk*

APOD: Jupiter and Io (2012 Nov 28)

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Oh, "hi io."

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