Is there any tool that can help me visualize this? If not, just how big and how visible would Jupiter would be in night/day sky compared to moon/sun? And how often would it be visible?

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    $\begingroup$ There actually is a planet in the asteroid belt: Ceres, which contains 40% of the asteroid belt's total mass, and would be considered a planet in its own right if it weren't part of a larger debris field. It's now classified as a dwarf planet (similar to Pluto). $\endgroup$ Commented 2 days ago

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It would be bright, but not super-bright.

Simulation using Stellarium shows that Jupiter has a peak magnitude of about -3.5 from Ceres, which orbits in the main asteroid belt. This is less bright than Venus is from Earth, but significantly brighter than any other planet. It has an apparent diameter, at opposition, of just over 1 arcminute, and so would be too small for the naked eye to resolve as a disc, and so would appear to be star-like.

The moons would probably remain hard to observe, as they would still be close to the planet, but it is at least possible that skilled observers would be able to see the moons with the naked eye, perhaps using an occluding disc to cover the brightness of the planet.

It would be visible for about half the time, when it was above the local horizon. There would be periods when it was close to the sun in the sky and so invisible. But the situation is not fundamentally much different from being on Earth.

The view from other asteroids, such as Jupiter's Trojans, would be different, but generally less bright.

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    $\begingroup$ Just for comparison purposes on that magnitude, Jupiter has a mag of -2.7 from Earth, and Venus is always close to -4.5. So at -3.5, Jupiter as seen from Ceres is just about twice as bright as the brightest Jupiter ever gets for us, but only half as bright as Venus seen from Earth. $\endgroup$ Commented 2 days ago
  • $\begingroup$ FWIW, here's a plot of Jupiter relative to Ceres (in the ecliptic plane) for 1974-Oct-1 to 2034-Jan-1, with a 90 day timestep. The horizontal line is the equinox direction. i.sstatic.net/cGNd86gY.png $\endgroup$
    – PM 2Ring
    Commented 2 days ago

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