Waking up with conjunction-itis | Astronomy.com (2024)

There’s something special about conjunctions. They’re surreal, like laughter in a dark hallway. Rather suddenly, two or more celestial luminaries come together. The pattern lasts a single night. You’ll never see it again … well, not exactly.

What a contrast from the permanence astronomy normally offers. Orion’s familiar belt and the W of Cassiopeia were etched into our childhood memories, at least subconsciously. They even may be imprinted on our nervous systems, as humans have stared at them for untold millennia. They don’t merely look familiar; they feel familiar. Not so with conjunctions.

The year’s best happens this month. It’s a four-way affair involving some of the night’s brightest luminaries. The Moon, Venus, Jupiter, and Aldebaran (Alpha [α] Tauri) all come together at 4 a.m. local time July 15.

Start with that crescent Moon, which always conveys a hint of lunacy — especially this waning crescent with its surrealistic slant. Illuminated on its left side, it’s a specter confined to the predawn hours normally reserved for REM sleep. Earthshine eerily makes its dark portion fluoresce.

Below that enchanted Moon floats Venus, the Morning Star. But it’s not just any appearance of our sister planet. This is Venus at its most luminous. At magnitude –4.7, it’s an amazing 75 times brighter than Vega (Alpha Lyrae), the most brilliant star that’s out, in the west. Venus is easily brilliant enough to cast shadows.

You won’t see Venus shadows on the 15th because the Moon dominates. But wait a couple of days until the planet stands by itself. Check it out a few hours before sunrise. If you’re away from all artificial lights — after all, it’s summer and maybe you’re on vacation — look for your shadow on any white surface like a beach (or you can create such a surface by spreading out a bed sheet). There’s your Venus shadow!

Only three celestial objects can cast shadows. (Stable shadows, that is. We won’t count the brief jumpy ones made by lightning or fireball meteors.) Sun and Moon shadows look the same because a light source’s size determines the nature of its shadows, and those two disks have the same sky width. Venus, a dazzling dot, is totally different. Its shadows lack fuzzy edges. Your body by Venus-light casts a stark outline. It seems drawn on the ground with a fine-point pen. It looks like nothing else. When you later tell friends, “I cast a Venus shadow this morning!” you will observe the further oddity of blank reactions.

It’s a four-way
affair involving
some of the night’s
brightest luminaries.

But back to the Morning Star’s brilliant meet-up with other luminaries. The uppermost is Jupiter, returning for its annual nine-month visibility window after hiding behind the Sun. And the fourth participant is the orange giant Aldebaran. Although it’s the 13th-brightest star in the heavens, it’s dwarfed by the brilliance of the others.

As insurance against clouds on the 15th, observe the meeting of Venus, Aldebaran, and Jupiter the preceding week, though the Moon will be elsewhere. You’ll also enjoy lots of meteors. The Perseid shower is several weeks away, but ample “sporadic” meteors materialize every morning before dawn. That’s because the direction Earth is heading in its orbit is then high overhead, which makes the air above your location plow through the maximum number. The rate is six an hour — one every 10 minutes.

This month’s predawn view puts you in the driver’s position in other ways, too. The direction you’re moving due to Earth’s rotation is toward the conjunction, at roughly the speed of sound.

You can even look toward where our solar system whizzes at a breathtaking 140 miles per second (225 km/sec) as it partakes in our galaxy’s spin. We rotate toward Deneb (Alpha Cygni), currently the highest star in the west. Finally, the direction the entire Milky Way is heading, relative to the group of galaxies we inhabit, is visible as well: It’s nearly overhead.

It’s rare to view all four of our celestial motions at once. That morning, you face forward in every way. Too bad space lacks a wind to blow your hair back.

Venus’ wonderful morning apparition will linger through the autumn. But its maximum brilliance is confined to July alone. By summer’s end, the Morning Star will have lost half of its light. So, as they say on TV, “Hurry up, this offer won’t last!”

At 4 a.m., the dazzling mélange of Venus, Jupiter, Aldebaran, and (on July 15) the Moon grabs attention like a gorilla in a yoga class. It dominates everything. Nonetheless, check out the single lonely star low in the south. This is the oft-overlooked Fomalhaut (Alpha Piscis Austrini). It’s the most isolated bright star in the heavens. A near-twin of Vega, Fomalhaut also matches Vega’s 25 light-year distance. It’s little-known only because it never climbs high, except in places with llamas or kangaroos.

Venus at its most glorious. The lonesome Fomalhaut. A streaking meteor every few minutes. The year’s best conjunction. The straight-ahead direction for all our celestial travels. Morning Star shadows. And this entire tapestry unfolds in the enchanted predawn stillness that yields only to birdsong and Crayola colors.

It’s the stuff of dreams. Worth setting an alarm to swap out with yours. And while you’re at it, wake me, too.

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