APOD: Moons and Jupiter (2009 Jul 14)

[nstahl]

I was very surprised to see the moons of Jupiter in that photo. They look visible to the naked eye in that picture, but we've been told Galileo discovered them with his telescope. There have to have been a lot of sharp-eyed people back in those days before tv and computer screens and such; if they are that nearly obvious, why weren't they discovered and recorded earlier? Or could this photo have been altered/augmented?

http://apod.nasa.gov/apod/ap090714.html

From this Wikipedia article:

All four Galilean moons are bright enough that they could, if they were farther away from Jupiter, be sighted from Earth without a telescope. (They are, however, easily visible with even low-powered binoculars.) They have apparent magnitudes between 4.6 and 5.6 when Jupiter is in opposition with the Sun,[38] and are about one unit of magnitude dimmer when Jupiter is in conjunction. The main difficulty in observing the moons from Earth is their proximity to Jupiter since they are obscured by its brightness.[39] The maximum angular separations of the moons are between 2 and 10 minutes of arc from Jupiter,[40] close to the limit of human visual acuity. Ganymede and Callisto, at their maximum separation, are the likeliest targets for potential naked-eye observation. The easiest way to observe them is to cover Jupiter with an object, e.g. a tree limb or a power line that is perpendicular to the plane of moons' orbits.

[ChiefChuckalucky]

I am wondering what that speck of light is directly above Jupiter. I'm thinking it's a star, because it isn't in the plane of moons.

Great photo!

[stevei]

I am also skeptical that those dots are Jupiter's moons. Not only are they visible to the naked eye in the photo, but the separation between them and Jupiter seems quite large (especially the one on the right). Isn't it more likely that these points of light are distant stars coincidentally lining up near Jupiter in the photo?

[BMAONE23]

I remember seeing an orbital diagram and they are definitely like they are shown. If you were to take the Jupiter System and scale it to the size of the solar system, jupiter becomes the size of the sun and its moons fall in orbits similar to Mercury, Venus and Earth
http://lasp.colorado.edu/education/oute ... lilean.php

[Chris Peterson]

I was very surprised to see the moons of Jupiter in that photo. They look visible to the naked eye in that picture, but we've been told Galileo discovered them with his telescope. There have to have been a lot of sharp-eyed people back in those days before tv and computer screens and such; if they are that nearly obvious, why weren't they discovered and recorded earlier?

The Galilean moons of Jupiter are visible to the naked eye. Their typical brightness and separation is comparable to many visual double stars. The challenge with seeing them is that they are easily lost in the glare of Jupiter itself. The way I view them is to position myself so that a somewhat distant phone or power line blocks Jupiter. I've also seen kids with good eyes see the moons directly.

Some people may have noticed the moons in the past; very few would be in a position to record that information. There are similar examples: why wasn't Uranus discovered much earlier? It's a reasonably easy naked eye object. How about the rings of Saturn? They make that planet appear noticeably elongated to people with good vision (another case I've seen kids comment on). I assume that all of these were occasionally observed, and simply not recorded anywhere, so the information didn't come down to us.

[Chris Peterson]

I am also skeptical that those dots are Jupiter's moons. Not only are they visible to the naked eye in the photo, but the separation between them and Jupiter seems quite large (especially the one on the right). Isn't it more likely that these points of light are distant stars coincidentally lining up near Jupiter in the photo?

They are certainly Jupiter's moons. The orientation and separation are correct. When you view Jupiter, you occasionally will see a single background star enter the field in a position to resemble another Moon; I've never seen two stars do this, let alone four. Jupiter's moons are brighter than most stars- you'd need to be in a very bright cluster to get four stars that bright and that close together.

[rigelan]

Yeah, these definitely are the right distances to be Jupiter's moons. The four largest (Galilean) ones anyway. They are a significant angle away from Jupiter, and are quite a sight to see through binoculars. Night after night you can see their apparent positions change. If you don't have equipment to see any of the other astronomical items, such as gas clouds and nebulae very easily, Jupiter's moons are a great task for the introductory astronomer.

[neufer]

I am wondering what that speck of light is directly above Jupiter.
I'm thinking it's a star, because it isn't in the plane of moons.

Neptune (magnitude 7.8 ) & Triton (magnitude 13.5 ).

[aristarchusinexile]

...not recorded anywhere, so the information didn't come down to us.

Much information may have been well published, but libraries were and are, I am led to believe, often destroyed by conquering 'civilizations' who wanted to destroy the culture, heart, soul, intellect of the peoples conquered .. makes for easier assimilation into the Empire of New Barbaria, Province of Consensus.

[neufer]

I am wondering what that speck of light is directly above Jupiter.
I'm thinking it's a star, because it isn't in the plane of moons.

Neptune (magnitude 7.8 ) & Triton (magnitude 13.5 ).

Believing it to be a fixed star, "ChiefChuckalucky" is not credited with Neptune's discovery!

<<Galileo's drawings show that he first observed Neptune on December 28, 1612, and again on January 27, 1613; on both occasions, Galileo mistook Neptune for a fixed star when it appeared very close (in conjunction) to Jupiter in the night sky.



Believing it to be a fixed star, he is not credited with its discovery. At the time of his first observation in December 1612, it was stationary in the sky because it had just turned retrograde that very day; because it was only beginning its yearly retrograde cycle, Neptune's motion was far too slight to be detected with Galileo's small telescope. However, in July 2009 University of Melbourne physicist David Jamieson announced new evidence suggesting that Galileo was indeed aware that he had discovered a new planet. In one of his notebooks he noticed the movement of a background star (Neptune) on January 28 and a dot (in Neptune's position) drawn in a different ink suggests that he found it on an earlier sketch, drawn on the night of January 6, suggesting a systematic search among his earlier observations. However, any notification about the discovery hasn't found. If confirmed, it would move the discovery of Neptune back by over two centuries.>>

[geckzilla]

I was surprised to see Jupiter there at all considering there is a cloud in front of it. The optics in the photo confuse me.

[rigelan]

I opened up Kstars for that night, July 11th (Actually July 12th) at around 2 AM local time. Copied a picture here.

u Capricorn magnitude = 5.1
Neptune magnitude = 7.8
Jupiter magnitude = -2.6
Callisto magnitude = 5.7

The little blue dot below Neptune is NC 1408, a galaxy of some sort, I don't think its visible. (Mag 15)

And for some reason this program doesn't show me Triton. (I looked it up, triton shines at Magnitude 13.5)

Behind the word 'Jupiter' is the fourth moon.

jupiter.png (4.25 KiB) Viewed 5473 times

[bystander]

I am wondering what that speck of light is directly above Jupiter.
I'm thinking it's a star, because it isn't in the plane of moons.

Neptune (magnitude 7.8 ) & Triton (magnitude 13.5 ).

I opened up Kstars for that night, July 11th (Actually July 12th) at around 2 AM local time. Copied a picture here.

u Capricorn magnitude = 5.1
Neptune magnitude = 7.8
Jupiter magnitude = -2.6
Callisto magnitude = 5.7

Looks like μ Cap not Neptune

[neufer]

I opened up Kstars for that night, July 11th (Actually July 12th) at around 2 AM local time. Copied a picture here.

u Capricorn magnitude = 5.1
Neptune magnitude = 7.8
Jupiter magnitude = -2.6
Callisto magnitude = 5.7

Using Celestia it is clear from Jupiter's moons that this is July 11th at around 3 AM local time.

Neptune is definitely further from Jupiter than Callisto at that time consistent with:
http://apod.nasa.gov/apod/image/0907/lu ... 4_riou.jpg

OK... I concede: μ Cap it is.

Neptune is hidden in the clouds (or too faint) and Triton is a smudge on my computer screen.

[bystander]

<<Galileo's drawings show that he first observed Neptune on December 28, 1612, and again on January 27, 1613; on both occasions, Galileo mistook Neptune for a fixed star when it appeared very close (in conjunction) to Jupiter in the night sky.>>

Galileo's notebooks may reveal secrets of new planet
Science Centric | 9 July 2009

Galileo knew he had discovered a new planet in 1613, 234 years before its official discovery date, according to a new theory by a University of Melbourne physicist. Professor David Jamieson, Head of the School of Physics, is investigating the notebooks of Galileo from 400 years ago and believes that buried in the notations is the evidence that he discovered a new planet that we now know as Neptune.

[apodman]

I am also skeptical that those dots are Jupiter's moons. Not only are they visible to the naked eye in the photo ...

Your statement makes no sense. A photo is a photo, not a naked eye view. And there's no reason for skepticism, as (1) capturing Jupiter's moons in a photo like this is not difficult at all - the only trick was finding our moon sufficiently dimmed by clouds to be in the same photo, and as (2) these are Jupiter and its moons, guaranteed - one of the sights in the sky that can't be mistaken for anything else.

I was surprised to see Jupiter there at all considering there is a cloud in front of it.

Jupiter is very bright. You can see it through thin and not-so-thin solid cloud cover (and even light rain!), just as you can sometimes see the moon, the sun, and Venus through solid clouds (except maybe in NYC). Just kidding, you can see them in NYC too if you find a spot to get the lights out of your eyes.

The Galilean moons of Jupiter are visible to the naked eye.

My eyesight (corrected by glasses) is only average, and in the proper skies I make an exercise of sighting Jupiter's moons with the naked (with glasses) eye. It's not exceedingly difficult to see a couple of moons. The same goes for daytime sightings of Venus at its maximum elongation from the sun; I have even seen it when the sun is higher than Venus - it's all in picking a good sky, knowing where to look, and looking carefully. You can see M31 through light-polluted city skies (also a good exercise in naked eye viewing) and other things you wouldn't imagine. Jack Horkheimer used to recommend simply looking through an empty cardboard toilet paper roll to isolate objects for naked eye viewing.

When looking for Jupiter's moons, whether with the naked eye or in binoculars or a telescope, (1) it pays to know in what direction they are lined up - they are lined up roughly parallel to the ecliptic, so first get an idea of which way the ecliptic runs, and (2) it pays to know the size of the spread you are looking for - today's APOD is valuable in this regard because you can compare the size of the spread among Jupiter's moons with the size of our moon, or in a telescope you can compare the size of the spread with the size of Jupiter itself.

[DavidLeodis]

I am confused as to who took the photograph.

The credit indicates that it was Anne Riou, but the "This skyscape" link brings up the image in an Astrosurf forum where it seems to be credited to a Penn Kalet. My admittedly simple translation of the French caption to the image in the forum does seem to state that Penn Kalet claims to have taken the photo. Unless Anne Riou and Penn Kalet are the same person then who did take the photo I'll no doubt be suitably when I find out.

[Indigo_Sunrise]

I am confused as to who took the photograph.

The credit indicates that it was Anne Riou, but the "This skyscape" link brings up the image in an Astrosurf forum where it seems to be credited to a Penn Kalet. My admittedly simple translation of the French caption to the image in the forum does seem to state that Penn Kalet claims to have taken the photo. Unless Anne Riou and Penn Kalet are the same person then who did take the photo I'll no doubt be suitably when I find out.

Scroll several post down in that forum, and several of the posters are addressing someone named "Anne", so maybe that is her 'name' on that particular site..... Just a guess.

[DavidLeodis]

I am confused as to who took the photograph.

The credit indicates that it was Anne Riou, but the "This skyscape" link brings up the image in an Astrosurf forum where it seems to be credited to a Penn Kalet. My admittedly simple translation of the French caption to the image in the forum does seem to state that Penn Kalet claims to have taken the photo. Unless Anne Riou and Penn Kalet are the same person then who did take the photo I'll no doubt be suitably when I find out.

Scroll several post down in that forum, and several of the posters are addressing someone named "Anne", so maybe that is her 'name' on that particular site..... Just a guess.

Thanks Indigo_Sunrise. I did notice that some of the forum mentioned Anne. I suspect they are the same person but it is confusing, but then I'll admit that I'm easily confused.

[bystander]

Scroll several post down in that forum, and several of the posters are addressing someone named "Anne", so maybe that is her 'name' on that particular site..... Just a guess.

Thanks Indigo_Sunrise. I did notice that some of the forum mentioned Anne. I suspect they are the same person but it is confusing, but then I'll admit that I'm easily confused.

But then, the posts that mention Anne also mention apod. Maybe they got the name Anne from apod.

I tried to send an email to Anne Riou for clarification, but the address has been disabled.

Penn Kalet seems to mean head strong or obstinate in Breton (Celtic dialect of Britanny).

[DavidLeodis]

Scroll several post down in that forum, and several of the posters are addressing someone named "Anne", so maybe that is her 'name' on that particular site..... Just a guess.

Thanks Indigo_Sunrise. I did notice that some of the forum mentioned Anne. I suspect they are the same person but it is confusing, but then I'll admit that I'm easily confused.

But then, the posts that mention Anne also mention apod. Maybe they got the name Anne from apod.

Good point bystander. Unless there is a reply having a definite answer I guess I'm going to have to remain confused.

[penn kalet]

Hi,

I would not want that David is still confused , so I just wanted to explain that my name is Anne Riou and my nickname on Astrosurf Penn Kalet ("hard-headed" in Celtic ) !
Thank you for your interest in my picture !
I have no treatment to accentuate the satellites of Jupiter.
I used the 70-200 Canon lens with a focal length of 149, ISO 400, Av f4, Tv 0.8s.
Thank you again !

Penn (Anne )

(Please, excuse my grammatical errors and spelling)

[DavidLeodis]

Hi,

I would not want that David is still confused , so I just wanted to explain that my name is Anne Riou and my nickname on Astrosurf Penn Kalet ("hard-headed" in Celtic ) !
Thank you for your interest in my picture !
I have no treatment to accentuate the satellites of Jupiter.
I used the 70-200 Canon lens with a focal length of 149, ISO 400, Av f4, Tv 0.8s.
Thank you again !

Penn (Anne )

(Please, excuse my grammatical errors and spelling)

Thank you Anne.

Votre anglais est bien mieux que mon Français. I cheated there, as I used an online translation service.

[penn kalet]

I cheated there, as I used an online translation service.

Me too !!
(to check that I did not write too much nonsense !)

[DavidLeodis]

I cheated there, as I used an online translation service.

Me too !!
(to check that I did not write too much nonsense !)