An international team of astronomers, using the Very Large Telescope (VLT) located in Chile, observed for the first time from Earth a mysterious large dark spot in Neptune’s atmosphere. During the observations, a smaller bright spot suddenly appeared next to it, the likes of which astronomers had never seen before.
As ESO’s European Southern Observatory highlights, this is the first time a spot on Neptune has been observed directly from Earth. In general, these spots are considered commonplace in the atmospheres of giant planets. The most famous of these is Jupiter’s Great Red Spot. The first spot on Neptune was discovered in 1989 by the Voyager 2 spacecraft. However, a few years later, it suddenly disappeared. Subsequently, similar phenomena were repeated more than once.
“Since the first discovery of the dark spot, I have always wondered: what are these short-lived, elusive dark spots?” says Patrick Irwin, a professor at Oxford University. Until now it has not been possible to observe spots on Neptune directly from Earth. However, Irvin and his team used the VLT data and managed to get the long-awaited images.
These images have already helped shed new light on the possible nature of the mystery spots. Ground-based observations, for example, have shown that the spots are likely the result of darkening air particles in a layer below the main visible haze layer, as ice and haze mix in Neptune’s atmosphere. .
Using the Multi Unit Spectroscope Explorer, the researchers were able to separate reflected sunlight from Neptune and sunspots into their component colors and wavelengths. As a result, a three-dimensional spectrum was obtained that allowed the spots to be studied in much more detail than ever before. Different wavelengths correspond to different heights of parts of Neptune’s atmosphere. Therefore, the presence of the spectrum helped astronomers to clearly determine the height at which the studied dark spot is located. In addition, the spectrum provided information about the chemical composition of different layers of the atmosphere, giving the team of astronomers a clue as to why the spot appears dark. The observations brought another unexpected result.
“During the observation, we discovered a rare type of deep, bright cloud that had never before been identified, even with observations from space,” said study co-author Michael Wong, a researcher at the University of California at Berkeley. This rare type of cloud appeared unexpectedly and was seen as a bright dot next to a larger dark dot. Furthermore, the cloud was in the atmosphere at the same level as the main dark spot.
“This is a completely new type of object compared to the small high-mountain methane ice clouds that have been observed before,” the researchers conclude.
