You've probably caught sight of Jupiter and Venus at dusk this winter. The sky's two brightest planets have been slowly approaching each other for weeks. And the closer they draw together the more exciting the view. There's a kind of cosmic electricity generated when two bright celestial objects come together. Not the shocking kind but the anticipation of something special about to happen.
We won't have to wait long. On Wednesday evening, Jupiter and Venus will be closest — just 0.5 degrees apart, equal to one full-moon diameter. Shining side by side like a distant pair of luminous eyes, all you'll need is good weather to meet their gaze. Best views will be from an hour to 90 minutes after sunset. Just face the western sky and look up — they'll be impossible to miss. For planning purposes check the time of your local sunset at timeanddate.com/sun .
Both planets are covered in clouds which reflect a lot of sunlight, the reason they're so brilliant. Jupiter spans more than 11 Venuses, so you'd think it would be the brighter of the two. But Venus is four times closer, so the smaller planet noticeably outshines the gas giant.
I always enjoy planetary conjunctions because they give the appearance of objects almost touching. But as we just learned, planets lie at vastly difference distances. We only see them close together because they appear along the same line of sight, the same way you might see the moon line up above a church steeple.
The reason planets (or the moon and a planet) occasionally align is because we live in a pancake-flat solar system where all these objects orbit in nearly in the same plane. As we look out towards the planets from our from our mobile blue observatory, better known as Earth, our gaze is constrained to that plane, making it inevitable that near and far planets will occasionally fall along the same sight line.
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When they do, we see them paired up in conjunction. Because planets are always on the move, Venus and Jupiter will slowly separate after March 1. Two things make that happen. Venus is moving up and away from the sun (toward the east) from our perspective.
Meanwhile, Jupiter is sliding westward along with all the other stars in the western sky to make room for the spring-time constellations rising in the east. Earth's changing position along its orbit as it circles the sun causes the stars and planets in the eastern sky to slowly drift to the west over the seasons. The same motions that brought the two together will soon split them apart.
What happens though if you have cloudy skies? Venus and Jupiter will still be close for a few days, so you can continue to enjoy the show. You can also watch the conjunction online. Astronomer Gianluca Masi will livestream the event on both March 1 and March 2 starting at 2:30 p.m. Central Time on his Virtual Telescope website .
Aurora alert!
As if the conjunction weren't enough, space weather experts predict a significant G2 geomagnetic storm on Sunday night, Feb. 26. The cause is a combination of a coronal hole, a gusher of high-speed particles from the sun, and a coronal mass ejection, another shot of solar stuff caused by a flare on Feb. 24.
According to the latest forecast activity will start with a minor G1 storm, with aurora possibly visible low in the northern sky as early as nightfall. But the main show is expected after 9 p.m., probably from about 10 p.m. to 1 a.m. Find a place with an open view to the north with as few cities as possible in that direction for a good view. I'll post updates on the Astro Bob Facebook page .
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