David Wilson, age 10s of Bridgeport  Conn

Are there really double stars?

Gemini is the constellation of the Heavenly Twins. The stars Castor and Pollux mark the heads of the shining cherubs. Castor is now the fainter one, but in Roman days the two were more equally bright and looked more like twins. Actually, these two stars are not related, They are trillions of miles apart and moving away from each other at a great rate, However there are real twins and even triplets among the stars, Though the ancients who named the Gemini did not know this, The news had to wait until the faraway stars could be seen and studied through the telescope,

Certain starry tricks had been suspected for a long time. The Arabs named the star Algol with their word for demon. To them, Algol in the constellation of Perseus was an unreliable pointer star, For two and a half days, the demon star would shine bright and clear. Then it dimmed for a few hours. Much later, the orbit of Sirius was carefully checked and found to be wavy instead of smooth. The telescope showed that the spectrum of still other stars changed from time to time,

These antics could be explained only by strong influences near these changeable stars. Algol might be dimmed as a dark star nearby passed across it, eclipsing our view. Sirius could be pulled out of orbit by the gravity from a nearby star, Spectrums could be changed as two close stars blended and unblended their light. All this could mean that certain stars were really twins, or double stars, And so they were, One by one the twin stars appeared in the telescopes,

Double stars are so close that they appear as one to the unaided eye, In the vast reaches of space, they may be millions or trillions of miles apart, Algol and its twin are only 13 million miles apart, which is close for these double, or binary, stars. Some of the starry twins are so far apart that they change very little in a hundred years,

But change they must. For these binary stars are bound together by the pull of each other’s gravity. This keeps each one swinging around the other in an orbit, The two orbits look like the links of a chain. Each star moves around the central mass of the two, which is a spot closer to the heavier of the twins. The orbit made by the heavier of the twins is the smaller one of the two links.

Castor turned out to be a three‑in‑one triple star. And each of these triplets turned out to be a double star. Instead of being a twin to Pollux  Castor is sextuplets in his own right Mizar the star that bends the handle of the Big Dipper, is a double star. So are our neighbor stars Proxima and Alpha Centauri. In fact, hundreds of heavenly twins have been discovered. There may well be more starry twins and triplets than there are lone single stars like our sun. However, our Old Sol has a family of thriving planets to keep him company. So far, we have not discovered another star with a system of planets But this too, may only be because we have not yet made telescopes powerful enough to spot them,