If your birthday falls around this time of year, namely May 21 through June 21, you are, according to the western zodiac, a Gemini. As a birthday present I\u2019m going to present a star in the Gemini constellation. The star is named Castor.<\/p>\n
First we\u2019ll find it. Then we\u2019ll unwrap it. And, guess what? There\u2019s a surprise inside.<\/p>\n
The birthday candle is burning short on Castor\u2019s cake. Castor sets early these days, about three hours after sunset. And in a few weeks it will be gone for the season, so don\u2019t come whining to me if you miss it.<\/p>\n
Castor is roughly 300 trillion miles away. Its light takes 52 years to reach Earth. On the scale of the universe, this is next-door-neighbor close.<\/p>\n
Fortunately, Castor is now in the west so it\u2019s in the most viewable slice of the sky for most Saipan residents.<\/p>\n
Here\u2019s how to find Castor: If you wait until one hour after sunset this weekend, you\u2019ll notice, looking due west of Saipan, a bright star roughly 30 degrees over the horizon. This star is named Procyon.<\/p>\n
How do you measure 30 degrees? By using your fist: It\u2019s a built-in degree measurer. If you hold a fist at arm\u2019s length like you\u2019re presenting someone the Olympic torch, your fist will cover 10 degrees of vertical arc. So if you walk it up from the horizon three times, you\u2019ll be sighting 30 degrees over the horizon.<\/p>\n
Once you\u2019ve found Procyon, you can scan horizontally by 20 degrees (two fists) directly to the right, maintaining the same distance over the horizon. This will land you on a really bright object. This object is brighter than Procyon. It\u2019s the planet Jupiter.<\/p>\n
Jupiter, like all planets, is just passing through any given area of the sky. It\u2019s not a permanent fixture. So, while the stars maintain essentially fixed positions relative to each other, at least over the human lifespan scale of things, the planets aren\u2019t as well behaved. Therefore, you can\u2019t always use Jupiter to find Castor. We\u2019re just enjoying a chance alignment right now.<\/p>\n
Anyway, it\u2019s time to get diagonal now. Let\u2019s slant up and to the right of Jupiter by one fist. This will land us near two bright stars, though they\u2019re not as bright as Jupiter or even as bright as Procyon. These two stars are the Gemini twins. The brighter of them is Pollux, which is a little bit yellow or orange, and to the right of Pollux, and a little bit lower in the sky, is Castor.<\/p>\n
Like many textual descriptions, this sounds like gobbledygook until you try it. Then it\u2019s easy.<\/p>\n
Easy, yes. Foolproof, no: Let\u2019s not forget that it\u2019s predicated on one hour after sunset. This region of the sky is setting, so if you\u2019re late to the party, you\u2019ll have to adjust your sights lower.<\/p>\n
Anyway, now that we\u2019ve got our hands on Castor, let\u2019s unwrap it.<\/p>\n
And, surprise, surprise! Castor isn\u2019t really \u201ca\u201d star.\u00a0 No, it\u2019s actually six stars and they\u2019re doing a wacky cosmic dance.<\/p>\n
Castor\u2019s six-star array consists of three pairs of stars. Each pair is like a married couple: They are gravitationally bound to their counterpart. Furthermore, all the pairs are also gravitationally bound to the other pairs, so these stellar couples are doing the do-si-do around the dance floor, with little orbits spinning inside of bigger orbits.<\/p>\n
Maybe \u201cdo-si-do\u201d is a dated concept. So for you younger readers, I\u2019ll note that it\u2019s sort of like twerking, only different.<\/p>\n
Anyway, marriages among paired stars, known as \u201cbinary\u201d stars, aren\u2019t always marriages of equals. One star is often brighter than its companion. Although they are presumably created at the same time and from the same blob of stuff (e.g. hydrogen), they often have nothing else in common. Some are big, some are small. Some are cooler, some are hotter. Some will burn out quickly, while others will become cosmic geezers.<\/p>\n
Yes, there are a lot of odd couples up there. Physics, like Cupid, has a droll sense of humor.<\/p>\n
Although Castor looks like just one star to the bare eyeball, an amateur telescope can see the brightest of each stellar pair. In this case, of these three visible stars, two are bright and very close to each other. The third is sort of an outcast, dimmer and distant, the true odd-man-out in an already odd arrangement. This weird scene is a cool sight.<\/p>\n
But far cooler is simply knowing Castor\u2019s story. Nobody needs a telescope for that, just as nobody needs a telescope to appreciate the night sky in general. The sky is, in fact, full of interesting stories like Castor\u2019s. There is no price of admission for spectators.\u00a0 This is a present we can all enjoy, even if it\u2019s not our birthday.<\/p>\n","protected":false},"excerpt":{"rendered":"
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