NEW YORK (AP) — Venus will pass between the Earth and sun on Saturday during what's called an inferior conjunction.

But don't plan on seeing the linkup. The sight is extremely difficult to spot without special equipment and a trained eye.

“The glare from the sun makes it really, really difficult to see,” said Michelle Nichols with Chicago's Adler Planetarium.

A conjunction happens when two celestial bodies appear close together in the sky. It could be two planets, or a planet and the sun. An inferior conjunction of Venus happens when the planet swings between the sun and Earth.

Such an alignment happens about every 19 months because of how Venus and Earth orbit the sun. The moment of inferior conjunction happens around 9 p.m. EDT.

“Some people call that a Venus kiss because we're extremely close together,” said astronomer Geary Albright with James Madison University.

Venus has phases just like the moon. Before and after the conjunction, Venus looks like a thin crescent — though only telescopes can see it. Those looking for signs of the transition can watch Venus move from the evening to morning sky Sunday.

In the nights leading up to the conjunction, find a flat area and look near the horizon just after sunset to glimpse Venus before it sets. It appears as one of the brightest objects in the sky.

After the conjunction, Venus will be visible in the morning sky just before sunrise. Take precaution to not stare directly at the sun.

While this weekend's event isn't much of a visual spectacle, scientists say it's an opportunity to track how the planets shift in space.

“Get a chance to get to know Venus,” said Nichols.

Paul McCartney's “The Kiss of Venus” was partly inspired by a book chapter describing the inferior conjunction. And two upcoming NASA missions will put a spotlight on Venus, investigating how it formed and why it turned out so different from Earth.