The pleiades and star clusters

The Pleiades is a beautiful example of a star cluster. It is often called “the seven sisters.” There are many stories from mythology that are associated with the Pleiades star cluster. The Pleiades can be seen in the Constellation Taurus with the naked eye if you are in a location with a very dark sky and little light pollution. The Pleiades can be found by first finding the Constellation Orion with its 3 “belt” stars, then follow the line of the belt pointing to the Pleiades.

Picture credit: NASA, ESA, AURA/Caltech, Palomar Observatory

The Pleiades is considered an open cluster by astronomers, which means the stars in it are far enough apart that they are slowly drifting apart and their collective gravity is not enough to hold them together. But, they do move together in our galaxy. If a star cluster has stars closer together so that gravity is strong enough to keep them from drifting apart, they are referred to as a “bound cluster.” The Pleiades also exist in a nebula, a gas cloud in space that is referred to by astronomers as a “reflection nebula.” The Pleiades stars are mostly bright blue stars and are generally larger than our Sun. This makes for beautiful pictures. The Pleiades have also been important for astronomers refining methods for measuring distance. The Pleiades are about 440 Light-Years (LY) from Earth, within our galaxy. The most direct method for determining distance is the method called Parallax, which is a simple triangulation technique. Parallax can currently be done for stars out to about 500 LY. The Hubble Space Telescope results were compared to ground based telescopes to refine the distance estimate. Some sources say there are about 500 stars in the Pleiades, others say as many as 1000 or more. But with the naked eye we only see a few of them. Such a beautiful group of stars stands out to us even though it is small in the sky.

The Pleiades are mentioned in the Bible in Job 9:7-10, Job 38:31-33, and Amos 5:6-9. The Pleiades are always mentioned with Orion in these verses. This is probably because the names of the Constellations are very ancient and there has long been stories from different cultures about mythical characters that people have associated with the stars. The Greek myth for this has a trouble-maker named Orion who was chasing the seven sisters who were the daughters of Atlas. In the story the sisters were turned into stars so that Orion could not reach them. There are other similar stories to this that likely are from before the Greeks. However, the Bible mentions them to make points about God. The stars are far beyond our control. But God created the stars and controls them. I’ve often thought, why did God create so much beauty in the universe? He didn’t have to, but He did. I think it shows us his goodness and greatness. Job 9:7-10 has the following (NIV text; blue emphasis added):

7He speaks to the sun and it does not shine;
he seals off the light of the stars.                       
8He alone stretches out the heavens         
and treads on the waves of the sea.

He is the Maker of the Bear and Orion,
the Pleiades and the constellations of the south.

 10He performs wonders that cannot be fathomed,
miracles that cannot be counted.

Astronomers have discovered some puzzling things about blue stars and star clusters. Astronomers examine the spectra of the light from stars and infer things about the ages of the stars and how they formed. I question much of this because it goes well beyond real verification. I do not accept that we can know how old a star is just from observing it’s spectra. I also question accepted ideas on star formation, since you cannot actually see stars forming in dense nebulas. Blue stars are believed to be “young” by most astronomers, such as 100 million years or less. Blue stars are large massive stars that burn up their hydrogen fuel very rapidly. So blue stars cannot last billions of years, yet there are many blue stars in our galaxy and most galaxies. I think you could argue these stars suggest the galaxy is younger than astronomers generally believe. If you accept that our galaxy is billions of years old but the blue stars are only millions of years old, then the blue stars would have to continue forming or they would have disappeared by now. This is the usual way scientists understand blue stars. But it possible to view the galaxy as young and then the blue stars, being some of the youngest objects in it, are an indicator of the young age of the galaxy. This is advocated in this article by astronomer Jason Lisle ( ). This is relevant to the Pleiades since it is a cluster of blue stars.

A mystery recently discovered about star clusters is from NASA’s Chandra X-Ray observatory satellite. In studying star clusters, the age of the stars is inferred from their light as mentioned above. Accepted theories would have expected the stars in a cluster to form from inside-out, since the denser regions of a collapsing cloud would be deeper in the interior. So scientists expected the older stars in the cluster to be closer to the center, but they found this was often wrong. The older stars were in the outer regions of the cluster. The reason for this is unknown. I would say astronomers reasoning about the ages of objects is often wrong. Certainly there is a need for more research on star clusters and what is truly going on in them. To see the NASA article on this go to

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