Alert fans noticed something amazing on the Game of Thrones finale: when Sam walked into the Citadel library, the chandelier had a sphere that looked suspiciously like the mechanical sun on the Game of Thrones opening credits. And it was the same thing. It’s called an astrolabe, and we have all the details about it.

Here’s what you need to know.

The Armillary Sphere or Astrolabe Can Track Stars and Perhaps Seasons on ‘Game of Thrones’

An “armillary sphere” also known as spherical astrolabe, armilla, or armil, shows up in the title credits of Game of Thrones. It’s that thing we see right at the start which seems to represent the sun, and has marking that depict battle scenes. You can see a photo of it at the very top of this article.

In the season 6 finale, when Sam finally gets into the library at the Citadel, he we see what appears to be this exact same object dangling from the roof in the middle of the library.

Here is what Sam saw in the library:

And here it is up close:

We wanted to known more about this “armillary sphere” thing, so we first consulted the Maester of the internet: Wikipedia. The Greek astronomer Hipparchus (c. 190 – c. 120 BCE) credited Eratosthenes (276 – 194 BCE) as the inventor of the armillary sphere. The name of this device comes ultimately from the Latin armilla (circle, bracelet), since it has a skeleton made of graduated metal circles linking the poles and representing the equator, the ecliptic, meridians and parallels.

Usually a ball representing the Earth or, later, the Sun is placed in its center. It is used to demonstrate the motion of the stars around the Earth. Before the advent of the European telescope in the 17th century, the armillary sphere was the prime instrument of all astronomers in determining celestial positions.

This means that we might get a glimpse of the “astronomy” around the planet at some point. It also indicates that this armillary might be used to help track the seasons. With long winters and such, the seasons are hard to track and are very different from Earth. The Citadel must be tracking the changes somehow if it can send out a white raven to indicate a season has changed. This is likely how they do so.

Reddit has a great discussion about this interesting find too, which you can see here.

This May Indicate that Sam or Another Maester Changes the ‘Map’ We See in the Opening Credits

Some think that this is the first sign that Game of Thrones may ultimately be Sam’s retelling of the events of Westeros. This would explain the opening credits using the same astrolabe that Sam finds in the Citadel. Perhaps he makes the tiny Westeros map and updates it as he tells the story of Westeros and the fight for the Iron Throne.

Giving further credence to this idea is that the glasses that the Maester in the Citadel uses for magnification also just happen to be very similar to what the viewer “sees through” when he’s viewing the map during the opening credits.

Here are the glasses the Maester uses:

And here is what we see through to view the map in the opening credits:

Which we then peer through, to see the map:

This just lends more credence to the idea that a Maester at the Citadel (hopefully Sam) is reading the Song of Ice and Fire. Which means that everything we’re seeing might have actually taken place in the past. A Redditor posits that this might also mean that history is written by the victors, so maybe the Lannisters aren’t as terrible as we “see” them as being.

The Astrolabe May Also Harness the Power of the Sun to Light the Map

How does the sun contraption work? Well, first of all, they probably don’t want to allow candles or lanterns inside the Citadel, so the books don’t catch on fire. Instead, they’ll harness the power of the sun and mirrors to light up the library. That’s why this mechanical contraption produces light, in addition to keeping track of the seasons and the motions of the stars. So it’s not only an astrolabe but also a sunlight projector or a heliostat. The Ancient Egyptians used these.

It might be helpful to note that the astrolabe is all about the history of Westeros. Each blade represents a different battle, as shown in the intro. The first blade is the conquest of Westeros by Aegon the Conqueror. The second blade shows the stag, the wolf, and the lion beating the dragon (aka the Baratheons, Starks, and Lannisters defeating the Targaryens.) Then we see all of Westeros bowing to the stag (Baratheon.)

I wonder how Sam will change the blades next?