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Are Neptune’s Disappearing Clouds Connected to the Solar Cycle?

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Astronomers have made a remarkable discovery – a connection between Neptune’s shifting cloud abundance and the 11-year solar cycle. This cycle, which is marked by the waxing and waning of the Sun’s magnetic fields, drives solar activity.The link between Neptune and solar activity is especially interesting because Neptune is in the distant reaches of our solar system, and receives only 0.1% of the sunlight that Earth does. And yet it seems that solar activity is influencing the planet’s cloud cover, rather than its four seasons, which each last around 40 years.

This connection was discovered by a team of astronomers led by Imke de Pater, who is an emeritus professor of astronomy at the University of California (UC) Berkeley. The team observed data from NASA’s Hubble Space Telescope, the W. M. Keck Observatory in Hawaii, and the Lick Observatory in California for 30 years. They noted that the clouds normally seen at Neptune’s mid-latitudes began to fade in 2019.

This finding came as a surprise to de Pater, who said: “I was surprised by how quickly clouds disappeared on Neptune. We essentially saw cloud activity drop within a few months.” Even four years later, according to Erandi Chavez – a graduate student at the Center for Astrophysics /Harvard-Smithsonian (CfA) – cloud levels remain low.

For now, the only visible clouds on Neptune are those hovering over the planet’s south pole. Researchers are now eager to understand why this sudden shift in cloud cover has occurred, and its potential implications for our understanding of solar activity. The discovery of this link between Neptune and the Sun is a fascinating one that could lead to further breakthroughs in our knowledge of our home star system.

A journey of Discovery to the Sun and Neptune.

As any astronomer will tell you, Neptune is an incredibly beautiful and complex planet. With its bright blue atmosphere and white ice caps, it’s truly a sight to behold. Yet, this beauty has become even more fascinating as we study the intricate relationship between this distant world and our own star – the Sun.
For years, scientists have been observing the changes in Neptune’s atmosphere as it moves around its orbit. Led by Dr. Christina Chavez and her team, they have been cataloguing images from the Keck Observatory from 2002 to 2022, Hubble Space Telescope archival observations from 1994, and data from the Lick Observatory in California from 2018 to 2019.
These images have revealed the seasonal changes in Neptune’s cloud cover and its connection to our own Sun’s 11-year solar cycle. As the sunspot activity increases and the flares become more frequent, we witness more active weather patterns on Neptune, with its clouds shifting according to the intensity of our own star.
The Twilight Zone program and Hubble’s Outer Planet Atmospheres Legacy (OPAL) program have helped us to better understand the complexities of Neptune’s relationship with the Sun. These efforts have allowed us to track the planet’s changing appearance over time and better understand how its environment is affected by our star’s flux in activity.
Neptune’s Brightness Changes in Sync With Sun, But With A Two-Year Delay.
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The power of the Sun is an incredible thing. Its rays of light can have a profound impact on the planets in our solar system, including Neptune. Recent observations by the Hubble Space Telescope give us an unprecedented glimpse into the relationship between the Sun’s 11-year solar cycle and Neptune’s clouds.Scientists have discovered an interesting connection between the solar cycle and Neptune’s cloudy weather pattern. By analyzing 2.5 cycles of cloud activity over a 29-year span of Neptunian observations, researchers found that Neptune’s reflectivity increased in 2002 and dimmed in 2007. After that, the planet brightened again in 2015 and then darkened to the lowest level ever observed in 2020, where most of the clouds went away.

The team of scientists behind the discovery have found that two years after a peak in the solar cycle, an increasing number of clouds appear on Neptune. This is due to the photochemistry that happens high in Neptune’s upper atmosphere, which takes time to form clouds. The more intense ultraviolet radiation from the sun during the solar peak triggers this photochemical reaction, leading to a greater abundance of clouds.
These findings provide strong evidence for a correlation between cloud cover and solar activity on Neptune. But it’s not just about the number of clouds — the team also discovered a positive correlation between cloud abundance and Neptune’s brightness from sunlight reflecting off it. When the sun is at its stormiest, it causes Neptune to dim, while when it’s at its brightest the planet will become brighter as well.
Our solar system is a fascinating and ever-changing place. We can observe changes in brightness on the distant planet Neptune, and it appears to be in sync with the coming and going of clouds on the planet. Surprisingly, according to a recent study, there is a two-year time lag between the peak of the solar cycle and the abundance of clouds seen on Neptune.So what’s causing the delay? It turns out that chemical changes on Neptune are caused by photochemistry, which happens high in Neptune’s upper atmosphere and takes time to form clouds. This process is key to understanding the correlation between the ice giant’s climate and the solar cycle.
The research team, led by Carlos Alvarez at Keck Observatory, used telescopes on Earth to study the climate of Neptune, located more than 2.5 billion miles away. The team’s observations have helped them constrain Neptune’s atmospheric models, which are essential for learning more about this distant world.The team has also observed more clouds in recent images taken during the same time that NASA’s James Webb Space Telescope observed the planet. These clouds were in particular seen at northern latitudes and at high altitudes, as expected from an increase in UV sunlight. This increase in UV light could produce more clouds and haze, but it could also darken them, thus reducing Neptune’s overall brightness.
Storms on Neptune rising up from its deep atmosphere can affect cloud cover too, but these storms are unrelated to photochemically produced clouds. As such, they can complicate correlation studies with the solar cycle. The research team is continuing to track Neptune’s cloud activity as new observations are made with Hubble, the Webb Space Telescope, Keck Observatory and Lick Observatory.


Are Neptune’s Disappearing Clouds Connected to the Solar Cycle?

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