Since Voyager 2 passed Neptune in 1989the giant black smudge that appears in the atmosphere of a distant planet presented a strange puzzle.
Now, for the first time, the specks can be observed in unprecedented resolution using terrestrial instruments, allowing scientists to understand why they appear so dark and why they are so different from those on other planets. It helps to elucidate whether
“Ever since dark spots were first discovered, I’ve always wondered what these short-lived, elusive dark features are.” Astronomer Patrick Irwin says PhD from the University of Oxford, UK.
“We are really excited not only to detect a dark spot from the ground for the first time, but also to record the reflectance spectrum of such a feature for the first time.”
neptune is dark vortex actually anticyclonic A storm like Jupiter’s Great Red Spot, but different in some important and mysterious ways. First, they are relatively short-lived, appearing and disappearing every few years.
It is also believed that there are relatively few clouds in their centers compared to the storm eddies of Saturn and Jupiter. The clouds we can detect are fluffy white clouds that appear around the edge, probably the result of gas freezing into methane ice crystals as it lifts from low altitudes.
But Neptune’s distance and short vortex lifetimes made it difficult to learn more. Since 1994, the Hubble Space Telescope has been the only instrument capable of observing and tracking planets, and the range of wavelengths over which it can observe planets is limited.
But when a large storm vortex formed in 2018, Irwin and his team turned to another instrument, the Very Large Telescope’s Multi-Unit Spectroscopic Probe (muse). MUSE was able to detect sunlight reflected from Neptune and split it into constituent wavelengths to reconstruct her 3D spectrum of the planet.
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Because different wavelengths are associated with different altitudes in Neptune’s atmosphere, the researchers were able to determine the altitude of the scotoma. And they discovered something surprising: it didn’t seem to be a “hole” in Neptune’s atmosphere, after all.
Rather, the deeper color is thought to be the result of darkening particles in the layer of hydrogen sulfide beneath the top layer of Neptune’s atmospheric aerosol haze. The researchers think this may be the result of localized heating deep within the anticyclonic eddy, causing hydrogen sulfide ice to evaporate and reveal a darker eddy core. The researchers’ observations are consistent with the particles in the upper aerosol layer becoming smaller and less opaque.
They also discovered another surprise. It’s a bright cloud that accompanies a vortex. This wasn’t the methane cloud that often accompanies Neptune’s swirls, but a type of cloud that had never been seen before. It appeared to be at the same altitude as the dark vortex rather than higher in the atmosphere.
What this is, and whether the team’s proposed mechanism for Neptune’s atmospheric darkening is correct, will need further investigation. However, with the ability to observe Neptune from the ground, the answer seems to be much closer.
“This is an amazing improvement in humanity’s ability to observe the universe.” Astronomer Michael Wong said. PhD from the University of California, Berkeley.
“At first, we could only detect these spots by sending spacecraft like Voyager there. Then we were able to see them remotely using Hubble. Progress has made this possible from the ground.”
The study was published as: natural astronomy.