In 1986, in a flyby shooting, the Voyager 2 space probe took some of our first photos of Uranus. The planet looked blue-green and featureless, a planetary pokerface. In the decades since, we’ve learned that Uranus does have weather, visible as variations in color on the surface, and new photos from by the Keck II telescope in Hawaii (above) reveal the ice giant’s meteorology in more detail than ever before. The scalloped pattern near the equator is a ring of clouds; the busy, blue-flecked cap at the right end—the planet’s North Pole—are storms.
For sunny weather, try another planet: this one gets sunlight hundreds times weaker than we do on Earth, and the temperature of its upper atmosphere drops as low as -371 F, making it the coldest planet in the solar system.
Image via Lawrence Sromovsky, Pat Fry, Heidi Hammel, Imke de Pater/University of Wisconsin
After three-plus decades of exploring the gas giants, passing the orbit of Pluto, and reaching points beyond, Voyager 2 has found something interesting near the edge of the solar system: surprisingly magnetic fluff. Researchers document their findings in this week’s Nature.
Of course, this fluff isn’t made from the dust bunnies you find under your bed, the ‘Local Fluff’ (a nickname for the Local Interstellar Cloud) is a vast, wispy cloud of hot hydrogen and helium stretching 30 light-years across [Discovery News]. Astronomers already knew this fluff was out there near the boundary area between our solar system and interstellar space. What surprised them is that the fluff is much more magnetized than they’d expected.
Nobody expected to take it this far. When NASA launched two probes named Voyager 1 and Voyager 2 in the summer of 1977, scientists hoped the probes would get as far as Saturn during their five-year mission. Instead, the nuclear-powered explorers are still sending data home over 30 years after their launch, and are currently pushing through the boundary of our solar system into interstellar space.
A collection of five papers in tomorrow’s issue of the journal Nature [subscription required] analyze the data sent back from Voyager 2 as it reached a turbulent frontier known as the termination shock. The sun is constantly spewing out particles in all directions; as these particles move through the solar system, they are known as the solar wind. This wind pushes back against the interstellar plasma that exists throughout the galaxy. At the end of the solar system, the solar wind finally begins to lose out and its speed drops below the speed of sound (relative to the interstellar medium), resulting in a roughly spherical shell known as the termination shock front [Nobel Intent blog, Ars Technica].
Voyager 1 passed through the shock in a different region several years ago but vexed scientists by failing to send back data during that crucial transition. That made Voyager 2′s observations all the more critical. NASA says the probe encountered the termination shock over August 31 and September 1 of last year, and surprised researchers by crossing the boundary several times. The multiple crossings indicate that “the shock is not the steady structure that is predicted by the simplest theory,” says Len Burlaga of NASA’s Goddard Space Flight Center in Greenbelt, Md. “It is like a wave approaching a beach, that grows, breaks, dissipates, and then re-forms closer to shore” [Science News].