The stars shine brighter in winter than in summer due to the more stable and less turbulent atmosphere in the cold season, which reduces the effects of atmospheric turbulence on the light of the stars and makes them clearer and less twinkling.
In winter, the marked contrast between the very cold air near the ground and the warmer layers of air higher up enhances atmospheric turbulence. The air keeps mixing and rippling, which leads to an irregular deviation in the path taken by the light from the stars to our eyes. This agitation of the air causes the brightness of the stars to fluctuate rapidly, creating that famous twinkling effect. The more pronounced these air exchanges are, the more the stars seem to "blink." Typically, during cold winter nights, these turbulences are more intense, which explains why the stars generally appear to twinkle more during this time.
In winter, the air is generally colder and drier, unlike the summer season where high humidity tends to stabilize the atmosphere. However, cold and dry air often leads to more unstable and turbulent atmospheric layers. This instability enhances air movements and further disrupts the light coming from the stars. And indeed, these small air movements create the phenomenon we call twinkling. Sometimes, there are also more cold fronts, significant temperature differences, and dynamic weather phenomena in winter, all of which contribute to these additional turbulences that make the stars blink like distant little bulbs.
In winter, in the northern hemisphere, stars generally appear lower on the horizon. However, when observing stars close to the horizon, their light passes through a thicker layer of the atmosphere. The longer the light travels through the atmosphere, the more it encounters atmospheric disturbances, resulting in even more pronounced twinkling. As a result, when they are low during winter nights, stars appear to shimmer or blink more than when viewed high in the sky in summer. It's like looking at something through thick glass: the more it is tilted, the more it distorts.
In winter, the nights are simply longer, which provides more time to observe the starry sky. During these extended nights, the temperature drops, making the air denser and creating more atmospheric turbulence. This turbulence causes the light from the stars to flicker, giving the impression of a more intense twinkling. We enjoy the sky for extra hours, making this winter twinkling phenomenon much more remarkable and visible. The longer the observation time, the more we notice how much the stars seem to twinkle brightly.
In winter, certain human activities slow down: fewer lit terraces, fewer outdoor parties, fewer nighttime events. As a result, fewer artificial light sources spoil the night. Once the city's lights are diminished, the darkness of the sky becomes deeper. Consequently, the contrast between the stars and this very dark sky increases significantly, making their twinkling much more striking. This winter decrease in urban brightness also facilitates the observation of stars that are usually less visible, highlighting a richer and more intense starry sky. In short, with fewer distracting lights, our eyes easily notice this dance of twinkling stars, a phenomenon already amplified by the cold and dry air of winter.
The seasonal reduction of certain urban and agricultural lighting sources in winter allows for better observation not only of stars but also of fainter celestial objects, such as some galaxies or nebulae.
The fact that stars do not twinkle when observed from space proves that their twinkling is solely the result of terrestrial atmospheric disturbances.
In the mountains, the stars "twinkle" even more, as the colder and more turbulent air at high altitude enhances this phenomenon officially known as stellar scintillation.
Sirius, nicknamed 'the Dog Star', appears particularly bright and sparkling in winter. It is actually the brightest star visible from Earth after the Sun.
Winter nights generally provide better astronomical visibility due to a longer duration of darkness, cold and dry air reducing light scattering, and a often observed decrease in light pollution in rural areas or locations far from large cities.
In cold and dry weather, the atmosphere contains less water vapor, further limiting light diffusion. This allows for better visibility of the stars, making them appear brighter and more defined to the observer on Earth.
Planets twinkle significantly less than stars because they appear as disk-shaped (extended source). This apparent diameter minimizes the effect of atmospheric disturbances, making their brightness much more stable to the naked eye.
Sure! Here’s the translation: "Yes, when stars are observed from space, they do not twinkle, as they are no longer affected by Earth's atmospheric turbulence. Furthermore, very calm nights with a stable atmosphere significantly reduce the twinkling observed from Earth."
The apparent change in color of stars is due to atmospheric refraction. The atmosphere acts like a prism, causing the light from stars to undergo variable refractions, particularly in winter when atmospheric turbulence is often heightened. This makes the colors of stars appear more fluctuating to the human eye.
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