Happy eighth night of Chanukah! To finish things out, last but certainly not least, here’s my favorite of them all, Neptune:
- Neptune orbits so far from the sun, almost three billion miles that its takes 165 Earth years to orbit the sun once. So, in July 2011, we celebrated the first full year since it was discovered in 1846.
- When Voyager 2 flew through the Neptune system in 1989 — still the only time it’s been visited from Earth — it saw a planet that was much more active than what was seen on Uranus, with a giant storm, big enough to swallow Earth, called the Great Dark Spot in its southern hemisphere. By 1994, the Great Dark Spot had vanished, as (not) seen by Hubble, but there was a similar storm in the northern hemisphere. Voyager 2 also confirmed that Neptune has a very thin and dusty ring system.
- Neptune has 14 moons. The biggest of the bunch, Triton, was discovered just a couple of weeks after Neptune itself was. From there, it was over 100 years until Nereid, which is now known to be Neptune’s third largest moon, was discovered.
- Triton is the seventh largest moon in the solar system, is bigger than Pluto, and is the only big moon in the solar system that orbits its planet retrograde — backward, relative to the planet’s rotation.
- Here’s another crazy-Neptune-moon fact. Neso, orbits Neptune the usual way (prograde), but is the moon that’s the most distant from its planet. It’s over 30 million miles out on average, and takes over 26 Earth years to zip around one time. That’s longer than it takes Saturn to orbit the sun! It reaches out as far as almost 45 million miles, which is further than Mercury’s orbit around the sun (36 million miles).
- Neptune’s orbit, which averages 30 astronomical units (AU) from the sun (30 times the Earth-Sun distance, or a bit less than 3 billion miles) forms the inner boundary of the Kupier belt. The Kuiper belt is a band of frozen objects that extends to about 55 AU and is where the dwarf planets Pluto, Haumea, and Makemake are.
- Neptune’s winds are the strongest in the solar system, as fast as 1300 miles per hour. That’s nearly ten times stronger than a Category 5 hurricane on Earth.
- Even though Neptune is a billion miles farther from the sun and gets less than half the sunlight Uranus does, it’s warmer. This is at least partly because of an internal heating mechanism. Neptune gives off more then two and a half times as much heat as it gets from the sun.
We’ve done it. Another trip through the solar system down, and another Chanukah, too. Remember, if you like my writing, have a look at my Facebook page, and like it, if you like: http://www.facebook.com/scottskywatch . Thanks for reading these this week, and happy holidays, Merry Christmas, Happy Kwanzaa, happy solstice, and all the best in 2016.