Celebrity Solstice (6:30 p.m. EST) -- After Celebrity Solstice, Celebrity Equinox and Celebrity Eclipse, we wondered what celestial name Celebrity Cruises would invoke for its fourth Solstice-class ship, launching in 2011. But we had to wait for an auspicious date -- today's winter solstice -- for the cruise line to reveal the name of its next ship: Celebrity Silhouette.

Silhouette, you may be thinking, is not the most heavenly of names. But Celebrity spokeswoman Tavia Robb explained to us that, while the name is not "as blatantly celestial," it still fits with Celebrity's style of naming these ships. A silhouette is a dark image displayed against a light background, so the name plays with the themes of light and dark, just like the other names. For example, a solar eclipse is when the moon's shadow (or silhouette) blocks the light of the sun.

Fun fact: The main dining room on Celebrity Equinox is also called Silhouette.

Celebrity Silhouette will be a sister ship to the other Solstice-class vessels, sharing their design (larger standard cabins, the Lawn Club with its real grass and glass-blowing demonstration area, multiple onboard restaurants and a futuristic disco). No details have been revealed yet about whether this fourth ship will sport any design tweaks or program innovations. Celebrity is currently focused on the launch of the third ship, Celebrity Eclipse, in April 2010. Stay tuned for more reveals about that ship (perhaps on another auspicious date like a new moon or the vernal equinox).

--by Erica Silverstein, Senior Editor