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Tag: Uranus

  • Uranus Emits More Than Thought

    Uranus Emits More Than Thought

    Since Voyager 2 visited Uranus in 1986, scientists have debated the odd ice giant’s heat balance. The other giant planets of our solar system — Jupiter, Saturn, and Neptune — all emit much more heat than they absorb from the sun, indicating that they have strong internal heat sources. Voyager 2’s measurements from Uranus indicated only weak heat emissions.

    But a new study indicates that Uranus does, in fact, have an internal heat source contributing to its heat flux. The study combined observations with a global model of Uranus across the planet’s full 84-year orbit and concluded that Uranus emits 12.5% more internal heat than it absorbs from the sun. That suggests that Uranus may not be so different from its fellow giants, but the planet’s large seasonal variations and differences across hemispheres raise plenty of questions about the planet’s interior structure. (Image credit: NASA; research credit: X. Wang et al.; via Gizmodo)

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  • Seeking Uranus’s Spin

    Seeking Uranus’s Spin

    Uranus is one of our solar system’s oddest planets. An ice giant, it spins on its side. We originally estimated its rate of rotation using measurements from Voyager 2, the only spacecraft to have visited the planet. But that measurement was so imprecise that within two years, astronomers could no longer use it to predict where the planet’s poles were. Now a new study, drawing on over a decade of Hubble observations of Uranus’s auroras, has pinned down the planet’s rotation rate far more precisely: 17 hours, 14 minutes, and 52 seconds. While that’s within the original measurement’s 36-second margin of error, the new measurement has a margin of error of only 0.036 seconds. In addition to helping plan a theoretical future Uranus mission, this more accurate rotation rate allows researchers to reexamine decades of data, now with certainty about the planet’s orientation at the time of the observation. (Image credit: ESA/Hubble, NASA, L. Lamy, L. Sromovsky; research credit: L. Lamy et al.; via Gizmodo)

  • Why Icy Giants Have Strange Magnetic Fields

    Why Icy Giants Have Strange Magnetic Fields

    When Voyager 2 visited Uranus and Neptune, scientists were puzzled by the icy giants’ disorderly magnetic fields. Contrary to expectations, neither planet had a well-defined north and south magnetic pole, indicating that the planets’ thick, icy interiors must not convect the way Earth’s mantle does. Years later, other researchers suggested that the icy giants’ magnetic fields could come from a single thin, convecting layer in the planet, but how that would look remained unclear. Now a scientist thinks he has an answer.

    When simulating a mixture of water, methane, and ammonia under icy giant temperature and pressure conditions, he saw the chemicals split themselves into two layers — a water-hydrogen mix capable of convection and a hydrocarbon-rich, stagnant lower layer. Such phase separation, he argues, matches both the icy giants’ gravitational fields and their odd magnetic fields. To test whether the model holds up, we’ll need another spacecraft — one equipped with a Doppler imager — to visit Uranus and/or Neptune to measure the predicted layers firsthand. (Image credit: NASA; research credit: B. Militzer; via Physics World)

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  • Reinterpreting Uranus’s Magnetosphere

    Reinterpreting Uranus’s Magnetosphere

    NASA launched the Voyager 2 probe nearly 50 years ago, and, to date, it’s the only spacecraft to visit icy Uranus. This ice giant is one of our oddest planets — its axis is tilted so that it rotates on its side! — but a new interpretation of Voyager 2’s data suggests it’s not quite as strange as we’ve thought. Initially, Voyager 2’s data on Uranus’s magnetosphere suggested it was a very extreme place. Unlike other planets, it had energetic energy belts but no plasma. Now researchers have explained Voyager 2’s observations differently: they think the spacecraft arrived just after an intense solar wind event compressed Uranus’s magnetosphere, warping it to an extreme state. Their estimates suggest that Uranus would experience this magnetosphere state less than 5% of the time. But since Voyager 2’s data point is, so far, our only look at the planet, we just assumed this extreme was normal. (Image credit: NASA; research credit: J. Jasinski et al.; via Gizmodo)

  • Uranus’s Polar Cyclone

    Uranus’s Polar Cyclone

    Uranus is an oddity among the planets of our solar system. Where other planets spin around an axis roughly in line with their orbital axis, Uranus spins on its side, placing its poles in line with the sun. On Earth, the polar regions are naturally colder the equator, but that doesn’t hold true for Uranus. Yet new observations of the ice giant show that it, like the other planets with atmospheres in our solar system, has a polar cyclone.

    Those observations are thanks to improvements in radio astronomy over the past couple decades. Uranus’s odd orbital geometry means that each of its poles are hidden from Earth for 42 years at a time; the current northern-hemisphere spring marks our first view of Uranus’s northern pole since 1965. In the recent observations, researchers saw a bright spot on the pole, surrounded by a faint darker ring. The team modeled the temperature and gas composition necessary to match their observations and found that those patterns were consistent with a cyclone sitting at the northern pole. (Image credit: NASA/JPL-Caltech/VLA; research credit: A. Akins et al.; via Physics Today)