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Using ESO’s Very Large Telescope (VLT), astronomers have noticed a large dark spot in Neptune’s atmosphere, along with an unexpected smaller bright spot. This is the first time that a dark spot on the planet has been observed using a telescope on Earth. These sporadic features in Neptune’s blue atmosphere have baffled astronomers, but the new findings provide more insight into their nature and origin.
Large spots can often be seen in the atmospheres of giant planets. The most famous of these is Jupiter’s Great Red Spot. A dark spot on Neptune was first spotted in 1989 by NASA’s Voyager 2 space probe, but it disappeared a few years later. “Since the first discovery of the dark spot, I have always wondered what these ephemeral and elusive dark features are,” says Patrick Irwin, a professor at the University of Oxford (UK) and lead researcher on the study, which is published today in the journal Science. Natural Astronomy. Published.
Irwin and his team used data from the European Southern Observatory’s VLT to rule out dark spots caused by “brightness” in cloud cover. The new observations indicate that they are likely due to the presence of a deep, dark layer of aerosols below the more prominent vapor layer, where the mixing of ice and vapor occurs. It wasn’t easy to come to this conclusion, because dark spots are not always visible in Neptune’s atmosphere, and astronomers haven’t had a chance to study them in detail. That changed when NASA’s Hubble Space Telescope and the European Space Agency detected several dark spots in Neptune’s atmosphere, including one in the planet’s northern hemisphere that was first spotted in 2018. Irwin and his team immediately began studying this patch of land, Using an instrument ideally suited to these difficult notes.
This image shows Neptune observed with the MUSE instrument
From the European Southern Observatory’s Very Large Telescope – Image: ESO/P. Irwin et al.
Using the VLT’s Multi-Unit Spectroscopic Explorer (MUSE), the researchers were able to divide the sunlight reflected from Neptune and its spot into its component colors, or wavelengths, and obtain a three-dimensional spectrum. [1]. This means that they can study the macula in greater detail than was previously possible. “I am thrilled that not only was I able to observe a dark spot on Earth for the first time, but I was also able to capture a reflective spectrum from such a spot for the first time,” says Irwin. Since you are actually scanning different depths in Neptune’s atmosphere at different wavelengths, this spectrum allowed astronomers to more precisely determine the height of the dark spot in the planet’s atmosphere. The spectrum also provided information about the chemical composition of the different layers of the atmosphere, which in turn provided clues as to why the spot appears dark.
The observations also resulted in a surprise. “Thus we discovered a rare deep, bright cloud that had never been seen before, even from space,” said study co-author Michael Wong, a researcher at the University of California, Berkeley, USA. This rare type of cloud appeared as a bright spot next to the larger main dark spot. The VLT data showed that the new “deep bright cloud” was at the same level in the atmosphere as the main dark spot. This means that this structure is very different from the small “companion” clouds of methane ice at high altitudes that were previously observed.
With the help of the European Southern Observatory’s VLT telescope, astronomers can now study these types of spots from Earth. “This is a huge leap forward. At first, we could only observe these spots by sending a space probe, like Voyager, to them. Then we had the opportunity to monitor them remotely with Hubble. Now the technology is so advanced that we can do it from the ground up Z,” concludes Wong, jokingly adding, “This might make me obsolete as a Hubble observer!”
Nuts
MUSE is a 3D spectrogram that allows astronomers to observe an astronomical object, such as Neptune, in its entirety. At each pixel, the device measures the intensity of light as a function of color or wavelength. The resulting data forms a 3D sequence where each pixel of the image is supplied with a full spectrum of light. In all, MUSE measures over 3,500 colours. The device is designed to use adaptive optics, which counteract the effect of turbulence in the Earth’s atmosphere, resulting in sharper images. Without this combination of properties, it would not have been possible to study the Neptune dark spot from Earth.
source: iso
