Uranus surface temperature
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Surface Temperature of Uranus
Infrared Observations and Temperature Profiles
The surface temperature of Uranus has been extensively studied using various observational techniques. Infrared observations from the Voyager 2 mission provided significant insights into the thermal emission spectra of Uranus. These observations revealed that the effective temperature of Uranus is approximately 59.4 kelvins 1. The temperature profiles derived from these spectra indicate that temperatures are nearly identical at the poles and near the equator, but are slightly lower by 1 or 2 degrees at mid-latitudes in both hemispheres 1.
Near-Millimeter Brightness Temperature
Further studies using near-millimeter photometric measurements have confirmed these findings. The brightness temperature spectra of Uranus, measured between 0.35 and 2.0 mm, show a smoothly varying continuum with no strong unresolved spectral structures 2. These measurements have allowed for an empirical fit to the Uranian temperature spectrum, confirming the effective temperature to be around 59.1 kelvins 2.
Temperature Inversions in the Stratosphere
Additional observations have identified temperature inversions in the lower stratosphere of Uranus. Photometric data at 20 micrometers indicate a brightness temperature difference of 0.8 ± 0.5 K, suggesting a weaker temperature inversion than previously thought 3. This inversion is attributed to the absorption of sunlight by methane and aerosols in the stratosphere 3.
Energy Balance and Effective Temperature
The energy balance of Uranus, derived from Voyager IRIS data, further supports these temperature measurements. The bolometric Bond albedo of Uranus is approximately 0.300, leading to an equilibrium temperature of 58.2 ± 1.0 K 4. The effective temperature, derived from thermal spectra, is 59.1 ± 0.3 K, which is consistent with previous findings and represents a substantial improvement in accuracy 4.
Upper Atmosphere and Thermosphere
In the upper levels of Uranus' atmosphere, temperatures are significantly higher. Data from solar and stellar occultations indicate temperatures around 750 kelvins, primarily due to the presence of atomic and molecular hydrogen 5. This high temperature contributes to an extensive thermal hydrogen corona around Uranus, which affects the orbital lifetime of ring particles and biases the size distribution toward larger particles 5.
Conclusion
In summary, the surface temperature of Uranus is characterized by an effective temperature of approximately 59.1 kelvins, with slight variations across different latitudes. The presence of temperature inversions in the stratosphere and high temperatures in the upper atmosphere further complicate the thermal dynamics of the planet. These findings provide a comprehensive understanding of the thermal environment on Uranus, contributing to our broader knowledge of the outer planets in our solar system.
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