A Galilean Night (Oct 23rd)
Posted: Mon Oct 26, 2009 8:29 pm
Hi,
Looking at the photo supposedly showing the Gallilean moons of Jupiter, I was immediately struck by the fact that the moons are in the wrong plane. Surely they should line up with the moon since the Earth and its moon, and Jupiter and its moons are all in the plane of the planets. So the photo is either doctored, or those points of light are background stars.
I think it unlikely that the camera would be able to see the Galilean moons at all, especially with the glare of the full moon. Only 6 other stars are visible in the shot. If the moons were visible (magnitude ~5) then I think a lot more other stars would also be visible.
Also, the bottommost "moon" is about 25 arcminutes from Jupiter (measured by comparing it with the Moon's 30 arcminutes), which is about 2 and a half times the greatest separation, which, according to Wikipedia, is 10 arcminutes.
Lastly, at least 4 of the other stars in the shot are short streaks showing that this was quite a slow exposure. However, the "moons" do not show this at all.
So I think that the photo was doctored, with the Galilean moons being added in later.
Cheers,
Brent.
Looking at the photo supposedly showing the Gallilean moons of Jupiter, I was immediately struck by the fact that the moons are in the wrong plane. Surely they should line up with the moon since the Earth and its moon, and Jupiter and its moons are all in the plane of the planets. So the photo is either doctored, or those points of light are background stars.
I think it unlikely that the camera would be able to see the Galilean moons at all, especially with the glare of the full moon. Only 6 other stars are visible in the shot. If the moons were visible (magnitude ~5) then I think a lot more other stars would also be visible.
Also, the bottommost "moon" is about 25 arcminutes from Jupiter (measured by comparing it with the Moon's 30 arcminutes), which is about 2 and a half times the greatest separation, which, according to Wikipedia, is 10 arcminutes.
Lastly, at least 4 of the other stars in the shot are short streaks showing that this was quite a slow exposure. However, the "moons" do not show this at all.
So I think that the photo was doctored, with the Galilean moons being added in later.
Cheers,
Brent.