What exactly is a triple conjunction? One thing that’s sometimes meant by this terminology is one conjunction involving three planets or stars. But it can also refer to three conjunctions, each involving the same pair of planets, or a planet and a star. It’s this second meaning that we’ll be using in these studies.
As the planets travel across the sky day by day and night by night, though their normal direction is from East to West, we regularly observe times when from Earth’s perspective they reverse their direction of travel across the sky. A conjunction with a star or another planet that has recently happened can then be repeated, and then is repeated once more after the planet resumes its ordinary direction of travel, resulting in a series of three conjunctions, a “triple conjunction”.
There are typically several months between the separate occurrences of a triple conjunction. When the separation between two occurrences gets to be about a month or less, those two begin to merge into a single occurrence. It then becomes a double conjunction rather than a triple.