Just a little reminder: Look to the skies tonight and you'll notice an important part of our solar system is missing.

Tonight Saturn will shed its rings — or rather, the rings will hardly be reflecting any sunlight.

According to Astronomy Now:

Equinox is a twice-yearly event when the Sun lies directly above a planet's equator. For Saturn, this occurs every 15 Earth years and sees the Sun pass through the plane containing the giant planet's rings. The unique illumination geometry allows features to be discerned in unprecedented detail. As Saturn marches towards its 11 August equinox, the Sun's angle to the ring plane lowers, causing out-of-plane structures to cast long shadows across the rings' broad expanse, making them easy to detect.

The image above, from Hubble Space Telescope, shows Saturn's axis tilting. Each image is almost a year apart: "starting on the left in 1996, just after the last time the rings were edge-on, and ending on the right in 2000 when the rings had opened up significantly from our point of view."

Send an email to Meredith, the author of this post, at meredith@io9.com.