Sol Region Sight-Seeing Tour #1 – Castor

So what is this “Tour” you speak of?

The Tour? Why that’s a geeky idea I had to dig up all the fact and fiction about the stars around and including our Sun, known as Sol in science and science fiction. Ostensibly, as a bit of a learning experience while I go about the playing a video-game.

You see, I’ve been playing a “space flight simulator” video game I really love called Elite Dangerous that has excited my long interest in Astronomy.  The game is set in the future where humanity has moved out to begin to settle and explore our galaxy. As such the game includes a 1 to 1 online mock-up of our Milky Way Galaxy with as much as we know to be true added to it, and fairly realistic algorithms for what we don’t know, and a lot of fictional future-history and lore added to give it all some drama, and all kinds of different ways to “play” depending on your interests. From exploration, pvp & pve combat, mining, commodity trading, power play politics, passenger liner business, bounty hunting, and much more.

I wanted to explore some of the famous stars we know in our real night skies.

In the game there are some star systems that are “locked” where you are not allowed to visit unless you have done something or achieved something for the government that controls that system. One of those “permit locked systems” is Sol System: our species home solar system with Earth and all the planets we know. Having just earned this permit I planned on heading towards the center of the “bubble” of civilized space to do some sight seeing, but didn’t just want to visit Sol. No, I wanted to explore some of the famous stars we know in our real night skies… To research the known details, and compare that to the fictional details in the game and in other famous science fiction genre examples.

And so, without further ado…. The first stop on our tour!

1st in a series of posts inspired by Elite Dangerous, a space video-game that I’ve been playing; full of images, cool astronomy & science facts, and associated sci-fi & pop culture trivia.

Sol Region Sight-Seeing Tour – Stop #1:
Castor / α Geminorum


51 lightyears from Sol. 25th brightest star as seen from Earth (including the Sun). 2nd brightest star in constellation Gemini. This single very bright star as seen by the naked eye is in reality a sextuple star system: six stars that orbit each other in a complex way. In this case the system is made up of 3 binary pairs.


History & Trivia, Real and Fictional:

  • Reality: 
    • Star & Constellation names from Greek Myth: The Constellation Gemini is named for “The Twins” of Greek mythology, Castor and Pollux. The two brothers were fraternal twins, born of their mother, Leda, but inseminated by separate fathers. The brightest star in the constellation is the “head” of the twin Pollux, son of the god Zuess, who seduced the queen in the guise of a swan. (Now that’s an odd pairing.) The 2nd brightest star in the constellation forms the “head” of the other twin, Castor, fathered by her husband Tyndareus, King of Sparta.
    • Chinese Star & Constellation Name: In the Chinese Constellation of the “North River” Běi Hé, (which consists of the stars western society named Castor, Pollux and ρ Geminorum), Castor is known as Běi Hé èr or “Second Star of North River”. (Poor Castor, always playing 2nd fiddle to Pollux.)
    • 1718: First recorded as a double star by James Pound, though it may have been resolved into two sources of light by Cassini as early as 1678
  • Fictional References: Couldn’t find any cool sci-fi references to the Castor star system itself, but the Castor name certainly has appeared in some popular media.
    • Castor Troy, fictional character in the movie Face/Off (1997), portrayed by Nicolas Cage and John Travolta.
    • Castor, fictional character in the movie Tron: Legacy (2010), portrayed by Michael Sheen.
    • Project Castor, a set of male clones in the TV series Orphan Black (2013-2017), portrayed by Ari Millen.

System Details:

Nothing interesting in the system in the game other than the amazing sextuplet star formation and currently a couple of players’ parked Carriers near the primary. Data from Elite Dangerous below, matches fairly closely with what is known in real life.

  • Castor Aa: Class A (hot white or blue/white dwarf stars, 1.4 to 2.1) solar mass in size, ~10,000°K temp.)
    • Age: 130 Million years
    • Solar Mass (w/ 1 being our sun): 1.39861
    • Solar Radius (w/ 1 being our sun): 1.5508
    • Surface Temp: 9,761K
  • Castor Ab: Class M (red dwarf,low mass & temp stars, majority of stars in galaxy or Class M.)
    • Age: 130 Myrs
    • Solar Mass: 0.4052
    • Solar Radius: 0.5808
    • Surface Temp: 3266K
    • Orbit: 0.8 days @ 0.02AU (1 AU is mean dist from Earth to Sun) from Caster Aa.
  • Castor Ba: Class A
    • Age: 130 Myrs
    • Solar Mass: 1.4141
    • Solar Radius: 1.2473
    • Surface Temp: 7,055K
  • Castor Bb: Class M
    • Age: 130 Myrs
    • Solar Mass: 0.2617
    • Solar Radius: 0.4298
    • Surface Temp: 2571K
    • Orbit: 1.5 days @ 0.03AU from Castor Ba
  • Castor Ca: Class M
    • Age 130 Myrs
    • Solar Mass: 0.4062
    • Solar Radius: 0.5827
    • Surface Temp: 3228K
    • Orbit: 0.9 D @ 0.01AU around shared center of mass w/ Castor Cb
  • Castor Cb: Class M
    • Age 130 Myrs
    • Solar Mass: 0.5664
    • Solar Radius: 0.5800
    • Surface Temp: 4119K
    • Orbit: 0.9 D @ 0.01AU around shared center of mass w/ Castor Ca

The Orrery image from Elite is zoomed out all the way so you can see the primaries of the 3 pairs and their respective orbits around each other. The yellow pin is in primary of Castor A pair. Fairly close you see Castor B Pair in a relatively circular orbit around A. Those 2 pairs have a shared inner orbit on another plane inside the far distant orbit of the Castor C pair of red dwarfs.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Next Tour Stop ->

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