Kelsey Oseid releases her new book What We See In The Stars today so she shares some facts about the night sky to celebrate. 

Kelsey Oseid

Kelsey Oseid

Not all constellations are made of stars- some are made of shadows

While the system of constellations that is officially recognized by international astronomers today is largely based on Greco-Roman traditions of stargazing, not all cultures have restricted their skylore to the bright spots. Aboriginal culture in Australia uses a constellation called the "Emu-in-the-sky" made of the dark shadows that span field of the Milky Way.

The seventh planet from our sun was almost named "George."

Well, sort of. The planet was discovered by William Herschel in 1781, and he wanted to name it after George III, who was the King of Great Britain and Ireland at the time. But since the other planets had all taken their names from ancient gods, the astronomy community decided instead to name the newly discovered ice giant "Uranus," after Ouranos, the Ancient Greek god of the sky. Bonus fun fact: in ancient mythology, Uranus was the father of Saturn, and the grandfather of Jupiter.

Pluto is smaller than the Moon

After Pluto lost its full-fledged "planet" status in 2006 and was reclassified as a dwarf planet, many of us mourned. How could our beloved ninth planet be maligned in such a way?! It turns out, though, that there are valid reasons for the redefinition of what really constitutes a planet. And Pluto didn't really fit the bill- with a diameter of only 1,475 miles, it's actually significantly smaller than our own Moon, which has a diameter of 2,159 miles. Luckily, astronomy still recognizes the great importance of Pluto in our solar system, and it got its "day in the sun" (no pun intended) recently when NASA's New Horizons spacecraft became the first mission ever to closely explore the dwarf planet.

The shadows on the face of the moon are named after human emotions.

When early astronomers looked at the moon, they assumed the dark shapes that spotted its face were oceans and seas. They called them the "lunar maria"- Latin for "lunar seas"- and mapped and named them individually. Many were named after human feelings and states of mind, like "Mare Tranquillatus"- the Sea of Tranquility- and "Mare Crisium"- the Sea of Crises. Though we now know that the shapes we see on the moon are basaltic plains, not watery oceans, they are still known as the Lunar Maria and retain their poetic names to this day.

The north star hasn't always been the north star.

Thanks to the rotation of the Earth's axis, Polaris- the current "north star"- won't always be the northernmost bright star. The axis of our planet wobbles very slightly, so the stars pointed to by the North and South pole do change over time. Some Egyptian pyramids are believed to have been built to align with the star Thuban, which would have been the "north star" thousands of years ago.

The Ancient Greeks put the "lactic" in "galactic."

The term "galaxy" comes from the Latin "via lactea"- the Latin translation of "milky way." The ancients only knew the Milky Way as a broad stretch of soft light in the night sky. Thanks to modern science, we now know our Milky Way galaxy is just one of billions of galaxies in the known universe. But our use of the word "galaxy" to describe star systems throughout space is a relic of ancient humans' ideas about the sky.

Meteor showers are annual phenomena that occur when the Earth travels through clouds of debris left behind by comets and other celestial bodies.

As the Earth revolves on its path around the Sun, it periodically comes into contact with bits of dust and other debris. When these pieces- often fragments left behind in the wake of comets- come in contact with Earth's atmosphere, they burn up and can create flares of light that are visible from the Earth's surface as "falling stars."