The Moon begins its slow retreat back toward invisibility
A cada 29,5 dias, a Lua percorre um ciclo completo de luz e sombra — e neste sábado, 21 de junho de 2025, ela se encontra em seu quarto minguante, com apenas 25% de sua face iluminada. Em quatro dias, no dia 25, ela desaparecerá completamente do céu noturno, encerrando mais uma lunação antes de renascer como um fio de luz no horizonte. Esse ritmo, antigo como o próprio sistema solar, continua a organizar o tempo e o olhar humano sobre o céu.
- A Lua está em retirada: sua face iluminada encolhe noite após noite, restando apenas um quarto de sua luminosidade neste 21 de junho.
- Em apenas quatro dias, no dia 25 às 7h33, ela desaparecerá inteiramente — a lua nova marcará o fim de mais um ciclo completo.
- O mês de junho narrou um arco lunar inteiro: do crescente inicial no dia 3 ao plenilúnio do dia 11, e agora à lenta dissolução do minguante.
- Para observadores do céu, agricultores, maregrafistas ou simplesmente curiosos, saber onde a Lua está em seu ciclo determina o que se pode ver — e o que a escuridão revela.
Neste sábado, 21 de junho de 2025, a Lua ocupa o céu com apenas um quarto de seu brilho total. É a fase minguante — o momento do ciclo lunar em que a porção iluminada diminui progressivamente, noite após noite. Em quatro dias, no dia 25 às 7h33 da manhã, ela completará sua retirada e entrará na lua nova, encerrando mais uma lunação.
O calendário lunar de junho conta uma história completa. No dia 3, às 0h41, a Lua surgiu como um fino crescente. Ao longo de uma semana e meia, foi crescendo no céu até atingir seu ponto máximo: a lua cheia do dia 11, às 4h46, redonda e luminosa. A partir do dia 18, às 16h20, o processo se inverteu e o minguante teve início.
Esse padrão se repete com notável regularidade. Uma lunação — o intervalo entre duas luas novas consecutivas — dura em média 29,5 dias, tempo suficiente para a Lua atravessar quatro fases principais e suas transições intermediárias: crescente, gibosa crescente, gibosa minguante e minguante. Cada estágio transforma sutilmente a aparência do satélite no céu.
Os dados que registram essas fases são fornecidos pelo Instituto Nacional de Meteorologia do Brasil. Para quem observa o céu noturno ou planeja atividades que dependem da luz — ou da ausência dela —, conhecer o momento lunar importa. A lua cheia ilumina a paisagem; a lua nova entrega o céu às estrelas. O minguante de hoje oferece um meio-termo: luz suficiente para enxergar, mas não o bastante para apagar os astros mais tênues.
Em quatro dias, a Lua desaparecerá. E então, como tem feito por bilhões de anos, voltará a surgir — um fio de luz no horizonte ocidental, recomeçando o ciclo.
On Saturday, June 21st, the Moon hangs in the sky at a quarter of its full brightness, steadily diminishing. This is the waning phase—the part of the lunar cycle when the Moon's illuminated portion shrinks night after night, pulling back toward darkness. In four days, on June 25th at 7:33 in the morning, it will disappear entirely into the new moon phase, completing one of the Moon's eternal rhythms.
The lunar calendar for June tells a complete story. The month began on the 3rd at 12:41 in the morning when the Moon emerged as a thin crescent, just beginning to grow. For the next week and a half, it swelled in the sky—the waxing phase, when more and more of its face catches the Sun's light. By June 11th, at 4:46 in the morning, it had reached its fullest expression: the full moon, bright and round and commanding the night sky. Then the reversal began. On June 18th at 4:20 in the afternoon, the waning phase started, and the Moon began its slow retreat back toward invisibility.
This pattern repeats with remarkable consistency. Astronomers call it a lunation, or lunar cycle—the complete interval from one new moon to the next. On average, this cycle takes 29.5 days, a span long enough for the Moon to move through four distinct phases, each lasting roughly a week. But the Moon's journey is more nuanced than that simple division suggests. Between the new and full phases lies the waxing crescent and the waxing gibbous—the latter a swollen, almost-full Moon. Between the full and new phases comes the waning gibbous and the waning crescent. These intermediate stages, sometimes called interfases, mark the Moon's gradual transitions, the subtle shifts in its appearance as it moves through its cycle.
The data tracking these phases comes from Brazil's National Institute of Meteorology, an organization that monitors not just the weather but the celestial events that shape our skies. For anyone watching the night sky or planning activities that depend on moonlight—or the absence of it—knowing where the Moon stands in its cycle matters. A full moon floods the landscape with reflected sunlight. A new moon leaves the night sky dark, revealing the stars in their full glory. The waning phase, where the Moon sits today, offers a middle ground: enough light to see by, but not so much that it washes out the fainter stars overhead.
In four days, the Moon will vanish from the evening sky entirely. Then, just as it has for billions of years, it will begin to reappear, a thin sliver of light returning to the western horizon after sunset. The cycle will begin again.
Citações Notáveis
A lunation or lunar cycle is the interval between new moons, averaging 29.5 days, during which the Moon passes through four main phases lasting roughly seven days each— Instituto Nacional de Meteorologia (Inmet)
A Conversa do Hearth Outra perspectiva sobre a história
Why does the Moon's cycle matter to anyone who isn't an astronomer?
Because it's one of the few celestial events that touches daily life. Tides follow it. Animals behave differently under a full moon versus a new moon. Photographers and night sky watchers plan around it. Even historically, people marked time by lunar phases long before calendars existed.
So when you say the waning moon is 25% visible, what does that actually mean visually?
Imagine a circle. Right now, a quarter of that circle is lit up and facing Earth. The rest is in shadow. As the days pass, even that quarter shrinks—you'd see a thinner and thinner crescent in the sky until it disappears entirely.
And these interfases—the gibbous phases—those are real distinctions people can see?
Absolutely. A gibbous moon is visibly different from a crescent. It's fat, almost full but not quite. Most people don't have names for these phases, but if you watch the sky night after night, you see the shape changing constantly.
Why is the cycle always 29.5 days? Is that just how the Moon orbits?
It's more subtle than that. The Moon orbits Earth every 27.3 days, but Earth is also moving around the Sun. So from Earth's perspective, it takes the Moon about 29.5 days to return to the same phase relative to the Sun. That's why the cycle is called a lunation—it's the full dance between all three bodies.
If someone wanted to see the new moon on June 25th, could they?
No—that's the whole point. A new moon is invisible because it's positioned between Earth and the Sun. The sunlit side faces away from us. You'd have to wait until a day or two after to see the first thin crescent reappearing.