Gary Hershorn Mercury, Jupiter, and Saturn are aligned in the night sky, appearing closer together than they've been since 2000. When three planets move into such a conjunction, it's known as a planetary trio. Here's how to see the conjunction on Monday night. Visit Business Insider's homepage for more stories. Mercury, Jupiter, and Saturn are currently clustering together in the night sky. Monday is the final night that the three planets will be lined up and visible at twilight. They appeared the closest they'd been in more than two decades on Sunday, forming an equilateral triangle.