In a span from 1994 to 2022, images of the renowned blue world, captured from Maunakea on Hawaiʻi Island via the W. M. Keck Observatory and NASAs Hubble Space Telescope, have shown a near disappearance of these atmospheric formations, save for those collected around the worlds south pole.
The clouds hovering above Neptune are performing an unforeseen disappearing act. Its the first time in more than 3 years of observations that astronomers have actually witnessed such a thing.
Cloud formation on Neptune flows and drops over the decades. Credit: NASA.
All of this may be very normal– part of a long cycle of cloud development and disintegration connected to solar activity that is only now coming to light. However, its a really unexpected revelation that defies expectations given Neptunes distance from the Sun and its very little solar direct exposure.
Neptunes clouds are synced with the Sun
” I was captured off-guard by the quick disappearance of clouds on Neptune,” shared Imke de Pater, emeritus professor of astronomy at UC Berkeley and the senior author of the research study. “We saw a quick decline in cloud activity within a matter of months.”
The discovery was made by astronomers led by the University of California (UC) Berkeley as they observed a stable decline of cloud protection generally observed at Neptunes mid-latitudes, starting in 2019.
Erandi Chavez, who headed the study throughout her undergraduate years at UC Berkeley and is now a graduate trainee at Harvard Universitys Center for Astrophysics, added:
“Recent images reveal increased cloud presence, primarily in the northern latitudes and greater elevations. This aligns with the observed rise in solar UV flux over the past two years,” explained de Pater.
” Even 4 years later, the images we captured in June revealed that the clouds have not restored their previous presence. This is extremely unexpected, particularly when compared to Neptunes previous periods of low cloud activity, which were not nearly as remarkable or prolonged.”
While keeping an eye on Neptunes progressing clouds, the astronomers completely examined images taken between 1994 and 2022. What emerged from this data was an interesting pattern connecting Neptunes shifting cloud cover to the solar cycle– the roughly 11-year cycle during which the Suns magnetic field flips, resulting in variations in solar radiation.
Regardless of these uncertainties, one things for sure: Neptunes currently frenetic atmosphere is a lot more complicated but also more interesting than we believed.
” Its genuinely fascinating to use Earths telescopes to study the climate of a world situated more than 2.5 billion miles away,” noted Carlos Alvarez, a personnel astronomer at Keck Observatory and co-author of the research study. “Technological advances and our Twilight Observing Program have allowed us to refine Neptunes climatic models, which are vital for comprehending the connection in between the ice giants environment and the solar cycle.”
The Great Dark Spot as seen from Voyager 2. Credit: NASA.
When the Sun emits extreme ultraviolet (UV) light at the peak of its cycle, specifically the robust hydrogen Lyman-alpha emission, clouds on Neptune appear in greater numbers about two years later. The suns impact isnt alone in driving cloud coverage on Neptune. Storms from Neptunes deep atmosphere– made up mainly of hydrogen and helium with simply a little bit of methane– influence cloud cover as well, although these are unrelated to photochemically-induced clouds, possibly complicating solar cycle correlation research studies.
The suns impact isnt alone in driving cloud coverage on Neptune. The increase in UV sunshine could cultivate more clouds and haze, yet simultaneously darken them, lowering Neptunes overall brightness. Storms from Neptunes deep environment– comprised mainly of hydrogen and helium with just a little bit of methane– influence cloud cover too, although these are unassociated to photochemically-induced clouds, possibly complicating solar cycle connection studies.
Scientists will continue to observe Neptunes atmosphere for signs of cloud activity. In the last couple of years, some clouds have started to emerge accompanying increased solar UV activity. In time, Neptunes clouds will return to their previous splendor.
This connection, traced through 2.5 cycles of cloud activity covering almost three years of observation, showcases how Neptunes reflectivity increased in 2002 (reaching a brightness optimum), then dimmed in 2007, lightened up once again in 2015, and plunged to its lowest taped level in 2020, corresponding with the decrease in cloud presence. The shifts in Neptunes brightness seem to mirror the ebb and circulation of cloud formation, driven by the Suns solar cycle.
” These engaging data provide the most robust evidence up until now that Neptunes cloud cover correlates with the Suns cycle,” discussed de Pater. “Our findings provide support to the idea that the Suns potent UV rays might be setting off a photochemical procedure responsible for producing Neptunes clouds.”
This sequence of Hubble Space Telescope images narrates the waxing and waning of the quantity of cloud cover on Neptune. Credit: UC Berkeley.
Among the most iconic pictures of this blue giant was snapped by NASAs Voyager 2 during its 1989 flyby, exposing an enormous storm system named the “Great Dark Spot.” Ever since, dark areas and extra storms, including a substantial equatorial storm in 2017 and a large dark spot in northern latitudes in 2018, have actually emerged.
Neptunes methane-rich clouds are often whipped by supersonic winds– the swiftest recorded throughout our solar system. In truth, its these clouds of methane that discuss Neptunes blue marble appearance. Despite the reality it comprises a relatively small percentage of Neptunes environment, methane soaks up red wavelengths of light and shows blue light back into space.
The findings were reported in the journal Icarus.
Neptunes methane-rich clouds are frequently whipped by supersonic winds– the swiftest tape-recorded anywhere in our solar system. Scientists will continue to observe Neptunes atmosphere for indications of cloud activity.
When the Sun gives off extreme ultraviolet (UV) light at the peak of its cycle, specifically the robust hydrogen Lyman-alpha emission, clouds on Neptune appear in greater numbers about two years later. Furthermore, a connection was recognized in between cloud abundance and the worlds brightness. This makes sense since clouds show light and thereby make items brighter.