Astronomy

5 Days, 2 Spectacular Conjunctions

Saturn, Mars and Antares are shown on Sunday night August 21 two nights before their lineup. Mars is still the brightest of the bunch at magnitude –0.5. It will with Saturn at +0.4 and Antares at +1.0. Details: 35mm lens, f/2.8, ISO 400, 10 seconds. Credit: Bob King

Conjunctions of bright planets make for jewelry in the sky. This week, get ready for some celestial shimmer. If you’ve been following the hither and thither of Mars and Saturn near Antares this summer, you know these planets have been constantly on the move, creating all kinds of cool alignments in the southern sky.

On Tuesday night (August 23) the hopscotching duo will fall in line atop Antares in the southwestern sky at nightfall. Mars will sit just 1.5° above the star and Saturn 4° above Mars. Viewed from the Americas and Europe, the line will appear slightly bent. To catch them perfectly lined up, you’ll have to be in central Asia on the following evening, but the view should be pleasing no matter where you live.

This will be the scene facing southwest at nightfall from the central U.S. on Tuesday night August 23. The two planets and star form a compact gathering that’s sure to grab your attention. The moment of conjunction between Mars and Saturn occurs at 11:00 UT (7 a.m. Eastern Aug. 24), but they’ll be below the horizon at that time for the Americas and Europe. Credit: Stellarium

Nice as it is, the Mars-Saturn-Antares lineup is only the warm-up for the big event: the closest conjunction of the two brightest planets this year. On Saturday evening, August 27, Venus and Jupiter will approach within a hair’s breadth of each other as viewed with the naked eye — only 0.1° will separate the two gems. That’s one-fifth of a full moon’s width! While Mars and Saturn will be a snap to spot low in the southwestern sky during their conjunction, Venus and Jupiter snuggle near the western horizon at dusk.

Look for Venus and Jupiter right next to each other 4° (about three fingers held together horizontally) above the western horizon about a half-hour after sunset on August 27. This map shows the view from across the central U.S. at about 40°N latitude. The two planets will be closest at 22:00 UT (6 p.m. Eastern, 7 p.m. Central, 8 p.m. Mountain and 9 p.m. Pacific). Map: Bob King; source: Stellarium

To make sure you see them, find a place in advance of the date with a wide open view to the west. I also suggest bringing a pair of binoculars. It’s so much easier to find an object in bright twilight with help from the glass. You can start looking about 25 minutes after sunset; Venus will catch your eye first. Once you’ve found it, look a smidge to its lower right for Jupiter. If you’re using binoculars, lower them to see how remarkably close the two planets appear using nothing but your eyeballs. Perhaps they’ll remind you of a bright double star in a telescope or even the twin suns of Tatooine in Star Wars.

The two planets will be only 6 arc minutes apart Saturday evening and easily fit in the same field of view of a telescope at high magnification. Jupiter’s four brightest moons will be obvious. If you’re patient and wait for the air to settle, you’ll be able to make out Venus’s waxing gibbous phase. Credit: Stellarium

Have a small telescope? Take it along — Jupiter and Venus are so close together that they easily fit in the same high magnification field of view. Jupiter’s four brightest moons will be on display, and Venus will look just like a miniature version of the waxing gibbous moon. Rarely do the sky’s two brightest planets nearly fuse, making this a not-to-miss event.

Venus and Jupiter do a little square dance over the nights of August 26-28. Jupiter is headed westward toward conjunction with the sun, while Venus is moving away from the sun in the opposite direction from our perspective. Credit: Stellarium

If cloudy weather’s in the forecast that night, you can still spot them relatively close together the night before and night after, when they’ll be about 1° or two full moon diameters apart. I get pretty jazzed when bright objects approach closely in the sky, and I’m betting you do, too.

I also don’t mind being taken in by illusion once in a while. During a conjunction, planets only appear close together because we view them along the same line of sight. Their real distances add a dose of reality.

On Saturday evening Venus will be 143 million miles (230 million km) away vs. 592 million miles (953 million km) for Jupiter. In spite of appearing to almost touch, Jupiter is more than four times farther than the goddess planet.

The showpieces in this week’s conjunction parade: Jupiter, Venus, Mars and Saturn. Credit: NASA/ESA

That distance translates to the chill realm of the giant gaseous planets where sunlight is weak and ice is common. Try stretching your imagination that evening to sense as best you can the vast gulf between the two worlds.

You might also try taking a picture of them with your mobile phone. I suggest this because the sky will be light enough to get a hand-held photo of the scene. Photos or not, don’t miss what the planets have in store for earthlings this week.

Bob King

I'm a long-time amateur astronomer and member of the American Association of Variable Star Observers (AAVSO). My observing passions include everything from auroras to Z Cam stars. I also write a daily astronomy blog called Astro Bob. My new book, "Wonders of the Night Sky You Must See Before You Die", a bucket list of essential sky sights, will publish in April. It's currently available for pre-order at Amazon and BN.

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