Jupiter and Venus are executing something close to a celestial merger this weekend.

From the perspective of terra firma, again on Sunday morning they will appear almost close enough to each other to kiss.

They made their closest approach Saturday morning, but shortly before dawn Sunday the sight of the aligned planets “will be pretty good too,” said Karen Masters, an astrophysics professor at Haverford College.

» READ MORE: Stargazing around Philadelphia: Everything you need to know

“Venus and Jupiter are the two brightest things in the night skies and seeing them close together … always gives me a real sense of the celestial mechanics going on in our solar system.”

On Saturday, they made their closest encounter in six years, and they still will appear quite near each other on Sunday morning for the benefit of early rising participants in the Blue Cross Broad Street Run or others awake before the sun comes up.

But their relationship is doomed. For one thing, Jupiter is 11 times the size of Venus, and in subsequent days, they will be drifting apart ponderously.

» READ MORE: Broad Street run weather should be perfect for runners

When and where to look

The show will occur in the southeast sky right before daybreak. Venus and Jupiter will come nearest each other around 5 a.m.

From the universe’s vast perspective this might pass for a near-collision, and while it may look that way for those of us on planet Earth, Venus and Jupiter still will be separated by about 400 million miles, says Masters.

Because Jupiter is so much farther away, it will appear only about half as bright as Venus, notes space.com.

What’s so special about this weekend

These conjunctions aren’t all that unusual, but viewing conditions on Sunday morning should be unusually excellent, despite all the light interference around here.

The moon won’t be in the way, and skies will be clear. Plus, humidities are going to be so low that water vapor won’t be obscuring the vista.

You might have noticed that the Philadelphia skies have been about as blue as they get. Relative humidities the last two days have been a rarefied zone of lowness — a desert-like 13% Saturday afternoon, a level rarely experienced around here.

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Venus-Jupiter conjunctions aren’t all that uncommon, and the next one, March 2023, will occur at a time when people normally would be awake. However, they won’t be as close together, and who’s to say what the sky conditions will be like. Another one is due in May 2024, Masters said, but due to astronomical conditions it will be all but invisible.

In the very short term, the viewing windows should be wide open Saturday and Sunday mornings. If you’re up for it.