Neptune III

StarDate

When Voyager 2 flew past Neptune, 35 years ago, its list of discoveries included six moons, a set of rings, a giant storm, and an odd magnetic field. Mission scientists converted some of its observations of the field to sound. And scientists are still trying to understand the magnetic field today.

Neptune is the Sun’s most remote major planet. It’s about four times Earth’s diameter. Methane in its upper atmosphere absorbs red light, giving the planet a blue-green color.

Neptune is tilted on its axis at about the same angle that Earth is. Also like Earth, its magnetic poles don’t line up with its geographic ones. But on Neptune, there’s a much bigger angle between the two – about 47 degrees, versus about 11 degrees for Earth.

And while Earth’s magnetic field is generated near the center of the planet, Neptune’s is generated closer to its cloud tops than its core.

Scientists haven’t settled on an explanation for how Neptune’s field is generated. It may be powered by “bubbling” motions inside a hot, slushy layer of ammonia, methane, and water. However it’s generated, Neptune’s magnetic field is powerful and complicated – befitting one of the giants of the solar system.

Neptune is at its best this week. It rises at sunset and remains in view all night, in Pisces. It’s brightest for the year as well. But it’s so far away that you need strong binoculars or a telescope to see it.

Script by Damond Benningfield