Venus Is Putting on a Dazzling Show This Month
Look west on September 18, when the planet reaches peak brilliance. Here’s what makes it so bright and how to see its crescent through a telescope.
The brightest planet in our sky is putting on an especially dazzling show. On September 18, Venus will reach the greatest illuminated extent of its 2026 evening appearance, blazing low in the western sky after sunset.
What makes the event especially interesting is that Venus isn’t brightest when it looks “full.” Instead, the planet peaks in brightness while appearing as a crescent through a telescope—a result of a delicate balance between how much of Venus is illuminated and how close it is to Earth.
Why is Venus so bright?
Venus is the brightest planet seen from Earth and typically the third-brightest natural object in our sky, behind only the sun and moon. Part of that comes down to its proximity and size: Venus is one of Earth’s nearest planetary neighbors, and it’s relatively large for a rocky planet.
But it’s Venus’ permanent cloud cover that significantly boosts the planet’s brightness. “The composition of Venus’ atmosphere makes it extremely reflective. In fact, it reflects from 75 to 90 percent of the incident light,” says Alex Gianninas, an astronomy professor at Connecticut College. “This is the highest reflectivity, or, as astronomers call it, ‘albedo,' of any planet in the solar system.”
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In other words, much of the sunlight that strikes Venus is bounced back into space rather than absorbed. Combined with the planet’s proximity to Earth, that highly reflective cloud cover helps make Venus far more visible in our sky than the other rocky planets.
The atmosphere that makes Venus appear so brilliant also helps make the planet extraordinarily harsh. “The atmosphere on Venus is composed mostly of carbon dioxide and is over 90 times thicker than the atmosphere on Earth,” says Gianninas. That dense atmosphere drives a runaway greenhouse effect, pushing the planet’s average surface temperature to about 867 degrees Fahrenheit (464 degrees Celsius). That’s hotter than Mercury, even though Venus is much farther from the sun.
Why Does Venus Change Brightness?
Like the moon, Venus cycles through phases as its position relative to Earth and the sun changes. “The phases of Venus were first observed by Galileo in 1610 and served as important observational proof of the heliocentric model of the solar system proposed by Copernicus,” says Gianninas.
Its changing brightness comes from two factors: distance and phase. When Venus is on the far side of the sun from Earth, much of its illuminated hemisphere faces us, so it appears nearly full—but it is also farther away and looks smaller. As Venus swings closer to Earth, its apparent disk grows dramatically, even as less of its sunlit side faces us.
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“Somewhat counterintuitively, Venus achieves its greatest illuminated extent when it's in its 'crescent' phase because it is closer to the Earth and thus appears bigger, as opposed to when it is closer to 'full' because it is further away and thus smaller,” says Gianninas.
How to See Venus at Its Brightest in September
Around September 18, look toward the west shortly after sunset. Venus will appear as an extraordinarily bright, steady point of light and should be easy to spot, even during dusk. A clear, unobstructed western horizon will offer the best view, since Venus will sit relatively low in the evening sky. And don’t wait too long after sunset to look for Venus—the planet will set about an hour after the sun.
No equipment is required to enjoy the show. With a telescope, however, you can see the geometry responsible for all that brilliance: Instead of a round, fully illuminated disk, Venus will appear as a crescent.
