Neptune Hot Spot!
Way back at the 2005 AGU Meeting, someone suggested that Enceladus' polar "hot spot" could be repeated in other worlds, even Saturn herself. Just this June 15, this blog reported that Tethys and Dione are hot too, as predicted. Using the European Southern Observatory Very Large Telescope in Chile, astronomers have discovered yet another "hot spot." Neptune's South Pole is markedly warmer than the rest of the planet.
The upper left image was taken at a wavelength of about 17.6 microns, and shows temperatures in the troposphere. The South Pole is warmer than the rest of the surface by 10 degrees Celsius. Saturn's hot spot is also most visible at 17.6 microns. Lower two images, taken 6.3 hours apart, show temperatures in the stratosphere. Here the hottest area rotates around the pole. The ESO Press Release attributes this heating to the Sun.
When a significant discovery is made, observers will often come up with a half-baked explanation. If premature conclusions are not examined critically, they might find their way into textbooks. As on Saturn, the Uranus hot spot is concentrated within a few degrees of the pole. If the Sun caused polar hot spots, Earth's warmest region would be the poles not the tropics. Polar hot spots on Enceladus have no relation to the Sun. Analogs from other worlds hint that the heat source probably comes from within.
Neptune's upper atmosphere contains methane, which causes the planet to appear blue. However, most of the atmosphere is hydrogen and helium. Methane's freezing point is -182.5 degrees C, but Neptune's atmosphere has a temperature of -200 degrees. How CH4 can exist in the atmosphere, where it should be frozen into liquid, has been a mystery. The hot spot provides a mechanism to transport methane from a warmer interior. Methane issues from deep within Earth--recently astronomers have found that Titan also creates methane. Production of hydrocarbons also requires an internal source of heat.
Astronomers have never adequately explained how planets began forming at all. Since Pierre Laplace, we have used the theory that the Solar System collapsed from a gaseous nebula. However, gas particles colliding at orbital speed will not stick together unless those particles have the mass of mountains. Something else is needed to start planet formation, internal heat and magnetic fields.
Most physicists believe that the Big Bang created billions of tiny Black Holes. These typically had the mass of mountains in a volume smaller than a proton. If a few of these tiny holes collided with a gas cloud, their gravity would gather material around them. The Black Holes were too tiny to suck everything up, but the small amount they did eat gave off radiation which opposed gravity's inward pull. Eventually the Sun was orbited by many balls of rock and gas with warm cores, the beginnings of planets.
The Black Holes are still there, hidden within planetary cores. The tiny amount of matter that they consume is far less than the planets gain through meteor collisions. This small diet, converted into heat, would produce internal heat. Some of the Black Holes rotate, dragging some of the core with them. This rotation could power the dynamo of a magnetic field.
Like most of the planets, Uranus rotates anti-clockwise as seen from the North. Radiation from the core would turn gas into electrons and positively charged ions. A magnetic field is formed with the "positive" pole in the South. A Black Hole's magnetic field drives charged particles into polar jets. The Northern jet is composed of electrons which are absorbed by the atmosphere. The Southern jet is composed of heavier ions which penetrate the atmosphere to warm the South Pole.
Neptune's hot spot adds to similiar discoveries on Saturn and moons like Enceladus. Discovery of internal heat on many worlds hints at something hidden within. Heat from a Black Hole may be the origin of earthquakes, volcanoes, our islands and continents. A magnetic field guides compass needles and protects life from the radiation of Space. The possible role of Black Holes connects cosmology with the planet we live on. There is far more within planets than meets the eye.
More Space news at the new Carnival of Space.