1. In physics, it refers to two stars with extremely close masses. Because their gravitational pull is very close, they attract each other and rotate around each other without separating.

In modern literature, partners who have a very tacit understanding, are inseparable, and have a deep bond are usually called Gemini. For example, the NBA's former Celtics had two major stars, Anthony Walker and Paul Pierce, who were known as the "Celtic Twins."

2. Overview of "double stars" in astronomy:

(1) "Double stars" in astronomy refer to two stars orbiting each other. But sometimes two stars in the same line of sight appear to be together, but are actually very far apart. This is called an "optical binary."

The brighter of the two stars that form a binary star is called the primary star, and the dimmer one is called the companion star.

When some double stars orbit each other, a phenomenon similar to a solar eclipse will occur, causing the brightness of such double stars to change periodically. Such a binary star is called an eclipsing binary star or an eclipsing variable star.

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

(2) "Gemini" is one of the famous "Twelve Zodiac Constellations". If you extend the line connecting Beta Orion and Alpha Star to the northeast, you can encounter two bright stars not far apart. The brighter one is Beta Gemini (called "Pollux" in ancient my country), with a brightness of 1.14 magnitude. , is the seventeenth brightest star in the sky; the slightly dimmer star is Alpha Gemini (called "Pollux" in ancient my country), with a brightness of magnitude 1.97. In ancient Greek mythology, they were imagined as two friendly brothers - Castor and Pullox.

In fact, to be precise, these two stars are actually "six stars" each composed of six stars.