Part 3/14:
Neptune orbits at a staggering 4.5 billion kilometers from the Sun—about 30 astronomical units. Its immense distance renders the Sun a faint, tiny dot in its sky, illuminating it only one-thirtieth as much as it does Earth. This faint light, combined with its frigid temperatures averaging -201°C, makes ground-based observation incredibly challenging.
Completing an orbit around the Sun takes Neptune 165 Earth years, meaning we've only experienced one full Neptunian year since its discovery. Space probes have a similarly tough journey: traveling there requires over a decade, and only Voyager 2 has visited Neptune, doing so in 1989—thanks to a rare planetary alignment that occurs roughly once every 175 years.