What is Gemini?

1. physically refers to two stars with extremely close masses. Because their gravity is very close, they attract each other, rotate around each other and will not separate.

In modern literature, a very tacit, inseparable and deeply bound partner is usually called Gemini. For example, the former Celtics in the NBA, Antoine Walker and Paul Pierce, are two big stars, known as "Celtic Gemini".

2. Overview of astronomical "double stars":

(1) "Binary star" refers to two stars that surround each other in astronomy. But sometimes two stars in the same line of sight look together, but in fact they are far apart. This phenomenon is called "optical binary star".

Of the two stars that make up a binary star, the brighter one is called the main star and the darker one is called the companion star.

When some binary stars orbit each other, a phenomenon similar to solar eclipse will occur, which will make the brightness of such binary stars change periodically. This binary star is called eclipsing binary star or eclipsing star.

More than half of the stars in the Milky Way are binary stars, including Sirius, the famous first bright star. Sirius Sirius A has a mass of 2.3 solar masses, and its companion Sirius B is a white dwarf with a mass of only 0.98 solar masses.

(2) Gemini is one of the famous zodiac signs. Extending the connecting line between beta star and alpha star of Orion to the northeast, we can meet two bright stars that are not far apart. Among them, beta star of Gemini (called "Beihe III" in ancient China) is the seventeenth bright star in the whole day with the brightness of 1. 14. A little darker is Alpha Gemini (called "Beihe II" in ancient China), with brightness of 1.97. In ancient Greek mythology, they were imagined as two loving brothers-casto and Poole Jocks.

In fact, accurately speaking, these two stars are actually "six stars" composed of six stars each.