2023-08-27 04:00:17
Using ESO’s Very Large Telescope (VLT), astronomers have observed a large dark spot in Neptune’s atmosphere, along with an unexpected small bright spot next to it. It is the first time that a dark spot on the planet has been observed with a telescope (A telescope, (from the Greek tele meaning “far” and skopein meaning…) terrestrial. These occasional structures on the blue background of the Neptune’s atmosphere is a mystery to astronomers, and the new results provide further clues regarding their nature and origin.
Great spots are common structures in the atmospheres of giant planets, the most famous being Jupiter’s Great Red Spot. On Neptune, a dark spot was first discovered by NASA’s Voyager 2 in 1989, before disappearing a few years later. “Since the first discovery of a dark spot, I have always wondered what these ephemeral and elusive dark structures were,” explains Patrick Irwin, professor at the university (A university is an institution of higher education whose objective is the…) of Oxford (United Kingdom) and researcher (A researcher (fem. researcher) refers to a person whose job is to do…) principal of the study published today in the journal Nature Astronomy.
Irwin and his team used data from ESO’s VLT to rule out the dark spots being caused by a “thinning” in the clouds. The new observations (Observation is the action of attentively following phenomena, without the will to them…) rather indicate that these spots are probably the result of the darkening of air particles in a layer located under the main Visible haze layer, when ice and haze mix in Neptune’s atmosphere.
Coming to this conclusion was no small feat, as the dark spots are not permanent structures in Neptune’s atmosphere and astronomers have never before been able to study them in sufficient detail. The opportunity arose following the discovery by the NASA/ESA Hubble Space Telescope of several dark spots in Neptune’s atmosphere, including one in the planet’s northern hemisphere, first noticed in 2018 Irwin and his team immediately set to work studying it from the ground – with an instrument perfectly suited for these difficult observations.
Thanks to the MUSE (Multi Unit Spectroscopic Explorer) instrument of the VLT, the researchers were able to break down the sunlight reflected by Neptune and its spot into its different colors, or wavelengths, and obtain a 3D spectrum (1). They were thus able to study the stain in more detail than before. “I am absolutely thrilled to not only have been able to detect a dark spot from the ground for the first time, but also to have recorded a reflection spectrum of such a spot for the first time,” said Patrick Irwin.
Because different wavelengths probe different depths of Neptune’s atmosphere, the spectrum has allowed astronomers to better determine how high the dark spot is in the planet’s atmosphere. The spectrum also provided information regarding the chemical composition of different layers of the atmosphere, which helped the team understand why the spot appeared dark.
The observations also gave rise to a surprising result. “We discovered a rare type of deep, bright cloud that had never been identified before, even from space,” says study co-author and researcher Michael Wong at the University of California, Berkeley ( UNITED STATES). This rare type of cloud appeared as a bright spot right next to the main large dark spot, with VLT data showing the new “deep bright cloud” was at the same level in the atmosphere as the spot. main dark. It is therefore a completely new type of cloud compared to small clouds of high altitude methane ice (Altitude is the vertical elevation of a place or object above a level.. .) previously observed.
Thanks to ESO’s VLT, astronomers can now study structures like these spots from Earth. “This is a staggering increase in humanity’s ability to observe the cosmos. At first, we might only detect these spots by sending a spacecraft there, like Voyager. Then we gained the ability to distinguish them from a distance thanks to Hubble. Finally, the technology has advanced to allow us to do this from the ground”, concludes Michael Wong, before adding jokingly: “It might put me out of work as an observer of Hubble!”.
Notes
(1) MUSE is a 3D spectrograph that allows astronomers to observe an entire astronomical object, such as Neptune, in one go. At each pixel, the instrument measures the intensity of light as a function of its color or wavelength. The data obtained form a 3D set (In set theory, a set intuitively designates a collection…) in which each pixel of the image has a complete spectrum. In total, MUSE measures over 3,500 colors. The instrument is designed to take advantage of adaptive optics (Adaptive optics is a technique that allows real-time correction of deformations…), which corrects turbulence in the Earth’s atmosphere (The Earth’s atmosphere is the gaseous envelope surrounding the solid Earth. Dry air is composed…), which allows for sharper images than would otherwise be possible. Without this combination (A combination can be:) of characteristics, the study of a dark spot of Neptune from the ground would not have been possible.
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