As autumn arrives, days grow shorter and colors deepen, while the fading light urges both body and mind to adjust.  Astronomers explain how this season affects the sky — from the paths of stars to the cycles of the Sun.

Nature shifts its rhythm, the sky lowers, and people become more reflective. This season both unites and challenges us — some see in it color and beauty, others see melancholy and weariness. Yet we all agree on one thing: in autumn, the days grow shorter.

The American philosopher Carlos Castaneda (1925–1998), echoing ancient wisdom, once wrote: “We do not see things as they are; we see them as we are.”

Astronomers’ View of Autumn in the Sky

IVARS ŠMELDS, PhD (Physics), Senior Researcher at Ventspils University of Applied Sciences

When we look up at the sky, we see only a small section of the celestial sphere — as though we were standing inside a globe of stars. From the outside, it would appear as a sphere with Earth at the center and the sky stretching above and below. Because we’re so small, we can’t immediately sense that Earth is round — its surface appears flat to us. The same effect can be seen inside a planetarium. The sky is there, but it doesn’t seem infinite: we see only the visible upper part, and our sense of distance is relative — a plane may seem high in the sky, but in reality, it’s far closer than the stars.

We don’t feel Earth turning on its axis each day or orbiting the Sun throughout the year — just as we don’t sense motion while riding a train, even though the landscape rushes past the window. Because of this movement around the Sun, the stars seem to circle the Earth during a single day, though in reality it’s Earth that’s rotating. Over the course of a year, the Sun appears to travel across the entire celestial sphere, crossing the celestial equator twice and tracing a path known as the ecliptic. Seen from the pole, the Sun forms a circle parallel to Earth’s surface, explaining the polar day and night. From the equator, the Sun rises and sets at right angles to the horizon, and twilight descends swiftly.

In astronomical terms, autumn begins with the equinox — the moment when the Sun crosses the celestial equator and rises due east, setting due west. From then on, nights grow darker and more favorable for observation, especially in optical astronomy. In radio astronomy, the Sun causes no interference, so studies continue regardless of day or night.

At the end of December, more intense meteor showers are expected — most notably the Geminids. The northern lights are linked to solar activity and appear most vividly in darkness. Solar flares that trigger them can disrupt radio communication, satellites, and even power grids, and may briefly influence the human nervous system and mental state.

The greatest threat to humanity lies in processes of our own making — pollution and overpopulation. No danger from large meteorites is expected in the coming century. Astronomers can track the trajectories of such objects and, if necessary, adjust their course. We study radio emissions to understand how stars are born. There may never be final answers in this field, yet every observation adds to our understanding.

VLADISLAVS BEZRUKOVS, Mg. sc. ing., Researcher at Ventspils University of Applied Sciences

Earth’s axis is tilted by about 23.5 degrees, so our hemisphere receives varying amounts of sunlight throughout the year.

The autumn sky is alive with change. As night falls, the winter constellations begin to appear — Orion with its bright belt, the Pleiades sparkling like a handful of diamonds, and Sirius, the brightest star of the night. In October, the Orionids streak across the sky, born of Halley’s Comet, and in November, the Leonids take their turn.

This autumn brings a special visitor — the comet 3I/ATLAS, arriving from beyond our Solar System. Only the third interstellar comet ever observed, it was discovered this summer and already shows signs of activity, with a visible tail in which NASA telescopes have detected carbon dioxide and water ice. Although it will pass safely by, its visit gives us a rare glimpse of matter from another star system.

The 25th solar cycle has brought some surprises.  When it began in 2019, scientists predicted it would be weak, but the number of sunspots and the frequency of solar flares have been far higher than expected.

This results in powerful geomagnetic storms that can interfere with radio communication, satellites, and power networks. Yet even with the most advanced telescopes and supercomputers, the Sun continues to guard its mysteries.

Text by Rebeka Busule

Ventas Balss newspaper