Thousands of years ago, a stunning rhetorical question was put to a man named Iyov (Job) by someone with a remarkable knowledge of astronomy, and a certainty that mankind has only attained to in late-modern history.
As HaShem says to Iyov,
Can you bind the bonds of Kimah [the Pleiades] and loose the cords of Kesil [Orion]?
— Iyov 38:31
The question speaks to the physical connectedness of the stars of the Pleiades and Orion, which are on a short list of open clusters—a term in astronomy that refers to a group of stars that are gravitationally linked—that are visible to the unaided, human eye from the surface of the Earth.
According to James B. Kaler, Professor Emeritus of Astronomy, University of Illinois, there are fewer than 30 such open clusters, visible to the naked eye. Pleiades is one of them, and Orion is another.
According to the European Space Agency,
We are familiar with the constellations that we see regularly in the night sky – a distinctive pattern of stars. However, although these stars may form shapes that are recognisable to us here on Earth, they do not usually have any real link to each other, as they are often at different distances from the Earth, and are in fact very far away from each other. . . . clusters, on the other hand, are systems of stars that are held together by the gravity of their members.
— Stellar Clusters & Constellations, Introduction to the Universe
We know certain groups of stars are open clusters through astronomical spectroscopy, the study of astronomy using the techniques of spectroscopy, which originated with Isaac Newton’s optics experiments of 1666–1672.
Newton used the word “spectrum” to describe the rainbow of colours that combine to form the white light of the sun, revealed through a prism. Later scientists expanded on his work and, in the early 1800s, German physicist Joseph von Fraunhofer combined prism and telescope to observe the spectrum of various planets and stars; astronomical spectroscopy was born.
In 1842, Austrian physicist Christian Doppler proposed what became known as the Doppler effect (or Doppler shift), which is important to astronomy as it relates to electromagnetic waves such as light. The so-called redshift or blueshift of the spectrum of stars enables scientists to measure their radial velocities, the speed at which they are approaching or receding from us.
Professor Kaler was kind enough to confirm for me today that scientists have thereby been able to establish with certainty which clusters consist of stars that are bound together gravitationally as a group since some time in the late nineteenth century.
Remarkably, of all the stars that can be seen from the surface of the Earth, unaided, the book of Iyov clearly refers to two open clusters as being bound and tied together, respectively, well before mankind had the science and technology to know this with any certainty.
How, then, did the writer of Iyov know these two groups of stars are gravitationally connected?
As Amotz HaNavi (the Prophet Amos) writes,
He Who made Kimah [the Pleiades] and Kesil [Orion] . . . HaShem is His Name!
— Amotz 5:8