In the celestial theater of planetary spots, Jupiter’s Great Red Spot often steals the limelight, a tempestuous maelstrom stretching 10,000 miles wide that has been relentlessly spinning for centuries. However, other planets, including Neptune, have been known to harbor spots of their own, with Neptune’s Great Dark Spot being first captured by Voyager 2 in the 1980s, only to inexplicably disappear when the Hubble Space Telescope attempted to image it in 1994.

Now, Neptune’s elusive dark spot has been imaged from Earth for the first time, thanks to the European Southern Observatory’s Very Large Telescope (VLT). Lead researcher Patrick Irwin from the University of Oxford, who has been intrigued by these transient and elusive dark features since their first discovery, expressed his excitement at not only detecting a dark spot from the ground but also recording a reflection spectrum of such a feature for the first time. The research, published in Nature Astronomy, also revealed an unexpected bright spot next to the dark spot, believed to be an unusual type of cloud, demonstrating how astronomers can unravel the mysteries of distant solar system planets from Earth.

Neptune’s Great Dark Spot: Ground-Based Telescope Images Mysterious Atmospheric Feature

While Jupiter’s Great Red Spot, an epic storm 10,000 miles wide that has been raging for centuries, is the most famous planetary spot in our solar system, other planets have their own unique spots as well. One such is Neptune’s Great Dark Spot, first imaged by Voyager 2 during its flyby in the 1980s.

Ground-based Observation of Neptune’s Spot

In an intriguing turn of events, Neptune’s Great Dark Spot, which had seemingly vanished when the Hubble Space Telescope tried to image it in 1994, has been imaged again. This time, however, it was captured not from a spacecraft but from a ground-based telescope. The European Southern Observatory’s Very Large Telescope (VLT) has achieved the unprecedented feat of imaging a Neptune spot from Earth.

Lead researcher Patrick Irwin from the University of Oxford shared his excitement about the discovery, stating, "Since the first discovery of a dark spot, I’ve always wondered what these short-lived and elusive dark features are."

Deep Dive into the Dark Spot

When Hubble returned its gaze to Neptune in 2018, it found another spot in the northern hemisphere. This presented the astronomers with an opportunity to study a spot while it was present. They used an instrument on the VLT called MUSE (Multi Unit Spectroscopic Explorer) to obtain spectrographic data, which provided a 3D view of the spot by observing different levels of the planet’s atmosphere. The research suggests that the dark spot is created by darker air particles gathering beneath the hazy layer in Neptune’s atmosphere.

Irwin expressed his thrill at not only detecting a dark spot from the ground for the first time but also recording a reflection spectrum of such a feature.

Unexpected Discovery

In addition to the dark spot, the researchers also discovered an unexpected bright spot next to it, which they believe to be an unusual type of cloud. This discovery highlights how ground-based observations can contribute to our understanding of the atmospheres of distant solar system planets.

Co-author Michael Wong lauded this as a significant leap in humanity’s capability to observe the cosmos. Wong stated, "At first, we could only detect these spots by sending a spacecraft there, like Voyager. Then we gained the ability to make them out remotely with Hubble. Finally, technology has advanced to enable this from the ground."

The research has been published in the journal Nature Astronomy.

Takeaways

The ability to capture images of Neptune’s Great Dark Spot from Earth represents a significant advancement in our ability to study distant planets. This achievement underscores the importance of continual technological advancement in astronomy. Furthermore, the discovery of the bright spot next to the Great Dark Spot opens up new avenues for research and shows how much we still have to learn about our own solar system.