Terran Union 1.6 concludes human expansion within our solar system except for orbital platforms placed beyond the solar orbital plane and within the Kuiper belt, Oort cloud and Midway station.
Long before the external Dyson sections shell captures the solar wind that would otherwise travel beyond the Kuiper belt into the interstellar media, there are numerous energy stream lanes within and without the solar orbital plane.
Even with the advanced fusion engines, there are extended periods of hibernation required to travel from the inner solar system to the Midway station.
A stepwise colonization of the planets allows human immigration to proceed in shorter hops where periods of hibernation are less necessary than travel between stars.
So, it's immigration from Midway station rather than Earth to Alpha Centauri.
Although searches for other Earth-like planets is important, nearby star systems with many satellites to colonize is a far more effective star-to-star immigration.
If compared to the relative distances of the outer planets from each other, it becomes clear that investment in advanced spaceships spurs the immigration across our solar system.
Overview
Dark, cold and whipped by supersonic winds, giant Neptune is the eighth and most distant major planet orbiting our Sun. More than 30 times as far from the Sun as Earth, Neptune is not visible to the naked eye. In 2011, Neptune completed its first 165-year orbit since its discovery.
The planet's rich blue color comes from methane in its atmosphere, which absorbs red wavelengths of light, but allows blue ones to be reflected back into space.
Neptune is so far from the Sun that high noon on the big blue planet would seem like dim twilight to us. The warm light we see here on our home planet is roughly 900 times as bright as sunlight on Neptune.
Potential for Life
Neptune's environment is not conducive to life as we know it. The temperatures, pressures, and materials that characterize this planet are most likely too extreme, and volatile for organisms to adapt to. Keep in mind, however, that humans adapted to extreme environments even before balloons traveled high in our atmosphere.
Size and Distance
With an equatorial diameter of 30,775miles (49,528 kilometers), Neptune is about four times wider than Earth. If Earth were the size of a nickel, Neptune would be about as big as a baseball.
From an average distance of 2.8 billion miles (4.5 billion kilometers), Neptune is 30 astronomical units away from the Sun. One astronomical unit (abbreviated as AU) is the distance from the Sun to Earth. From this distance, it takes sunlight4 hours to travel from the Sun to Neptune.
Orbit and Rotation
One day on Neptune takes about 16 hours (the time it takes for Neptune to rotate or spin once). And Neptune makes a complete orbit around the Sun in about 165 Earth years (60,190 Earth days).
Sometimes Neptune is even farther from the Sun than dwarf planet Pluto. Pluto's highly eccentric, oval-shaped orbit brings it inside Neptune's orbit for 20-year period every 248 Earth years. This switch, in which Pluto is closer to the Sun than Neptune, happened most recently from 1979 to 1999. Pluto can never crash into Neptune, though, because for every three laps Neptune takes around the Sun, Pluto makes two. This repeating pattern prevents close approaches of the two bodies.
Neptune's axis of rotation is tilted28 degrees with respect to the plane of its orbit around the Sun, which is similar to the axial tilts of Mars and Earth. This means that Neptune experiences seasons just like we do on Earth; however, since its year is so long, each of the four seasons lasts for over 40years.
Moons
Neptune has 16 known moons.
Triton is the only large moon in the solar system that circles its planet in a direction opposite to the planet's rotation (a retrograde orbit), which suggests that it may once have been an independent object that Neptune captured. Triton is extremely cold, with surface temperatures around minus 391 degrees Fahrenheit (minus 235 degrees Celsius). And yet, despite this deepfreeze at Triton, Voyager 2 discovered geysers spewing icy material upward more than 5 miles (8 kilometers). Triton's thin atmosphere, also discovered by Voyager, has been detected from Earth several times since, and is growing warmer, but scientists do not yet know why.
Rings
Neptune has at least five main rings and four prominent ring arcs that we know of so far. Starting near the planet and moving outward, the main rings are named Galle, Leverrier, Lassell, Arago, and Adams. The rings are thought to be relatively young and short-lived.
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This Voyager 2 image, taken in 1989, was the first to show Neptune's rings in detail.
NASA/JPL
Neptune's ring system also has peculiar clumps of dust called arcs. Four prominent arcs named Liberté (Liberty), Egalité (Equality), Fraternité (Fraternity), and Courage are in the outermost ring, Adams. The arcs are strange because the laws of motion would predict that they would spread out evenly rather than stay clumped together. Scientists now think the gravitational effects of Galatea, a moon just inward from the ring, stabilizes these arcs.
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