1. About how much time passed between when Io began to pass behind the limb of J
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Question
1. About how much time passed between when Io began to pass behind the limb of Jupiter to when Io was completely obscured?
2. What is the amount of time it takes for a complete cycle of Ganymede?
3. What is the amount of time it takes for a complete cycle of Europa?
4. What is the maximum elongation of Callisto?
5. Starting from June 1, 2014, at 1:00 PM, what is which time is a viewing opportunity to see all moons on the same side of Jupiter? (To find the first viewing opportunity, expand in the horizontal graph and move time forward until all the lines are above the central line.)
6. In what constellation is Jupiter on June 1, 2014?
(Among these four, Virgo, Libra, Gemini, and Cancer, there is the answer)
Explanation / Answer
(1) Io orbits Jupiter at a distance of 421,700 km (262,000 mi) from Jupiter's center and 350,000 km (217,000 mi) from its cloudtops. It is the innermost of the Galilean satellites of Jupiter, its orbit lying between those of Thebe and Europa. Including Jupiter's inner satellites, Io is the fifth moon out from Jupiter. It takes Io about 42.5 hours to complete one orbit around Jupiter (fast enough for its motion to be observed over a single night of observation). Io is in a 2:1 mean-motion orbital resonance with Europa and a 4:1 mean-motion orbital resonance with Ganymede, completing two orbits of Jupiter for every one orbit completed by Europa, and four orbits for every one completed by Ganymede. This resonance helps maintain Io's orbital eccentricity (0.0041), which in turn provides the primary heating source for its geologic activity Without this forced eccentricity, Io's orbit would circularize through tidal dissipation, leading to a geologically less active world.
Like the other Galilean satellites and the Moon, Io rotates synchronously with its orbital period, keeping one face nearly pointed toward Jupiter. This synchronicity provides the definition for Io's longitude system. Io's prime meridian intersects the equator at the sub-Jovian point. The side of Io that always faces Jupiter is known as the subjovian hemisphere, whereas the side that always faces away is known as the antijovian hemisphere. The side of Io that always faces in the direction that Io travels in its orbit is known as the leading hemisphere, whereas the side that always faces in the opposite direction is known as the trailing hemisphere
(2) Ganymede is the seventh moon and third Galilean satellite outward from Jupiter, orbiting at about 665,000 miles (1.070 million km). It takes Ganymede about seven Earth days to orbit Jupiter.
Size: Ganymede’s mean radius is 1,635 miles (2,631.2 km). Due to its size, Ganymede can be viewed with the naked eye. Early Chinese astronomical records show the discovery of a moon of Jupiter, mostly likely the first observation of Ganymede. Although Ganymede is larger than Mercury it only has half its mass, classifying it as low density.Temperature: Daytime temperatures on the surface average -171F to -297F, and night temperatures drop to -193C. It is unlikely that any living organisms inhabit Ganymede.
Ganymede orbits Jupiter at a distance of 1,070,400 km, third among the Galilean satellites, and completes a revolution every seven days and three hours. Like most known moons, Ganymede is tidally locked, with one side always facing toward the planet. Its orbit is very slightly eccentric and inclined to the Jovian equator, with the eccentricity and inclination changing quasi-periodically due to solar and planetary gravitational perturbations on a timescale of centuries. The ranges of change are 0.0009–0.0022 and 0.05–0.32°, respectively. These orbital variations cause the axial tilt (the angle between rotational and orbital axes) to vary between 0 and 0.33°.
(3) Europa is the sixth-closest moon of Jupiter, and the smallest of its four Galilean satellites, but still the sixth-largest moon in the Solar System. Europa was discovered in 1610 by Galileo Galilei and was named after Europa, mother of king Minos of Crete, who became one of Zeus' lovers. Progressively better observations of Europa have occurred over the centuries by Earth-bound telescopes, and by space probe flybys starting in the 1970s.
Europa orbits Jupiter in just over three and a half days, with an orbital radius of about 670,900 km. With an eccentricity of only 0.009, the orbit itself is nearly circular, and the orbital inclination relative to Jupiter's equatorial plane is small, at 0.470°. Like its fellow Galilean satellites, Europa is tidally locked to Jupiter, with one hemisphere of Europa constantly facing Jupiter. Because of this, there is a sub-Jovian point on Europa's surface, from which Jupiter would appear to hang directly overhead. Europa's prime meridian is the line intersecting this point. Research suggests the tidal locking may not be full, as a non-synchronous rotation has been proposed: Europa spins faster than it orbits, or at least did so in the past. This suggests an asymmetry in internal mass distribution and that a layer of subsurface liquid separates the icy crust from the rocky interior.
The slight eccentricity of Europa's orbit, maintained by the gravitational disturbances from the other Galileans, causes Europa's sub-Jovian point to oscillate about a mean position. As Europa comes slightly nearer to Jupiter, Jupiter's gravitational attraction increases, causing Europa to elongate towards and away from it. As Europa moves slightly away from Jupiter, Jupiter's gravitational force decreases, causing Europa to relax back into a more spherical shape, and creating tides in its ocean. The orbital eccentricity of Europa is continuously pumped by its mean-motion resonance with Io. Thus, the tidal flexing kneads Europa's interior and gives it a source of heat, possibly allowing its ocean to stay liquid while driving subsurface geological processes. The ultimate source of this energy is Jupiter's rotation, which is tapped by Io through the tides it raises on Jupiter and is transferred to Europa and Ganymede by the orbital resonance.
(4) greatest elongation at Callisto can be up to 10.7 arcminutes from Jupiter, and should be visible with the naked eye if light from the planet is blocked off, perhaps by occulting it behind a building or a tree branch.
(5) On sunday, june 1: moon 5.4 degrees south of Jupiter is not long for the world; we'll watch the bloated behemothdescending lower in the western evening sky. Tonight, one will find it close to the waxing crescent moon. Despite its decreased altitude,Jupiter remains the brightest night sky object apart from the moon and Venus. Behold Zeus and Diana early this evening.
(6) The planets Venus and Jupiter have been drawing closer together in the evening sky over the span of the winter and the spring. Back in February, 2015, these planets were on opposite sides of the sky, since Jupiter was rising in the east while Venus was in the western sky after sunset. If you were watching all this time, you would have seen Jupiter creeping across the evening sky over the last three months, moving toward its July, 2015 rendezvous with Venus. By now in the month of May, these two bright objects are now sharing the same patch of sky, and are approaching a little bit more each evening!
After the sunset during May, you can see the position of these planets among the stars of the zodiac. During May, Venus will appear to be moving through the stars of the constellation Gemini. Jupiter is currently in the constellation Cancer, “the dark constellation,” formed of very faint stars. However, even from the brightly-lit cities, it should be easy to see that Jupiter is in between Gemini and the constellation Leo.
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