A team of scientists led by a Professor from the University of Oxford, Patrick Irwin, observed a dark spot on Neptune’s surface from the ground for the first time in a momentous display of the capacities of Earth based telescopes. “Since the first discovery of a dark spot, I’ve always wondered what these short-lived and elusive dark features are,” says Irwin.
The new findings have shown that the dark spots are not caused by a clearing of the clouds but most likely the darkening of particles in a deeper layer of the atmosphere. Furthermore, the researchers also made a surprising discovery, finding a bright spot right by the dark spot, composed of a rare bright cloud type never identified before.
Neptune is the outermost planet in the solar system and its distance of 4.5 billion kilometres from the sun makes it difficult to observe closely from the surface. Dark spots on its surface were first detected by the Voyager 2 probe on its flyby in 1989, however, their examination from Earth remained elusive since they dissipated after a few years.
More recently, in 2018, the Hubble telescope discovered the latest series of dark spots which inspired Irwin and his team to set about observing them from the Earth’s surface before they disappeared again. The team used the European Southern Observatory’s “Very Large Telescope”(VLT) in Chile for their discovery.
The telescope’s system of automated mirrors is able to self-adjust to minimise interference from Earth’s atmosphere in its observations. Furthermore, the VLT’s new measurement devices allowed the researchers to obtain a 3D spectrum, a detailed record of the wavelengths (colours) of light reflected by Neptune.
According to study co-author and Berkeley planetary scientist Michael Wong, the new observations herald a new stage in humanity’s power to observe the universe: “This is an astounding increase in humanity’s ability to observe the cosmos.
“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.”
