Getting Bullish on Star Clusters

Astronomers now believe that most stars are formed in clusters. Giant interstellar clouds of gas and dust produce dozens to hundreds of stars in fairly close associations. Then over millions of years, these families become more diffuse as the gravity of the rest of the galaxy tugs stars apart. Indeed, if our sun had siblings four-point-whatever billion years ago, they have long since fled their nest, leaving us well on our own.

The constellation Taurus (the bull) features two contrasting star clusters you can see with reasonably dark skies, the Hyades (the face of the bull) and the Pleiades (the seven sisters, above in infrared light; credit: NASA/JPL-Caltech). They aren’t really related; they just happen to be fairly close in a line of sight from Earth.

And as for the eye candy image at the top, infrared light highlights the dust in between the stars of the Pleiades. Most standard long-exposure images in visual light show a bluish hue around the stars.

In the chart above you see the Pleiades labeled. The Hyades are that “V” with Aldebaran, plus most of the other nearby stars. Bright Aldebaran (home of a certain Star  Trek whiskey) isn’t part of the Hyades, per se; it just happens to lie between Earth and the cluster behind it. In early Spring, these stars are all pretty high in the sky around sunset.

Here’s a brief comparison between the two clusters:

  Pleiades Hyades
core diameter 16 light years 18 light years
influence of gravity 86 light years 65 light years
age 115 million years 625 million years
distance 440 light years 151 light years
population 1,000 350
mass 800 solar masses 350 solar masses

 

That these clusters have stayed together so long, especially the Hyades, seems to go against the grain of thought that in our galaxy, clusters get ripped apart within about a hundred million years of being formed. The Hyades, especially, is something of an anomaly. But a logical explanation is that it once might have been huge, and what we see today as the head of the bull was once much more populated with suns–maybe thousands of them.

The Pleiades have three mentions in the Old Testament: twice in the Book of Job: 9:9 and 38:31, plus once by the prophet Amos (5:8). You can check the links above to catch some of the non-Christian  mythology behind these star formations. There’s quite a bit of interest behind this simple sun sign and the popular astrology behind it. I leave you off with an image of the Hyades with far more stars than you can see with your unaided eyes, especially in or near a city.

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About catholicsensibility

Todd and his family live in Ames, Iowa. He serves a Catholic parish of both Iowa State students and town residents.
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