( CNN ) The Hubble space telescope peers hundreds , thousands , millions of light-years into the universe to study novas , quasars and nebulas . But weeks ago , it pulled its focus way in close -- to just light-minutes away -- to view a rare and beautiful spectacle at the planet Jupiter . Three big moons crossed past it at the same time , casting their shadows onto Jupiter 's swirling surface . From the perspective of people theoretically standing on Jupiter , it would be like three solar eclipses happening at once , astronomers said . In the last 15 years , this has happened only twice , the Space Telescope Science Institute said . `` The next one will be 2032 , '' said astronomer Carol Christian . So , Hubble shot photos rapid fire to capture the rare conjunction in late January . And STScI published them Thursday , along with a short fast-motion video animation . There was no great scientific gain in Hubble taking the snaps . The moons and their crossings have been examined plenty and are well-known . `` We felt that there are images which have aesthetic value above and beyond their scientific value , '' said astronomer Zolt Levy . It was a gift of beauty to the public . Jupiter is a sort of mini-solar system inside our solar system . It 's the largest body after the sun . And like the sun , it comprises a lot of helium and hydrogen gas , but it does n't have enough mass to burst into the intense nuclear fusion that makes the sun a fireball , NASA says . It has many satellites , including 62 moons , and they swarm around the planet with many of them crossing the surface facing Earth constantly . But only four of them are highly visible standouts . They are Io , Europa , Ganymede and Callisto . The four moons are called the Galilean satellites , because Renaissance astronomer Galileo Galilei discovered them in 1610 , when he pointed his telescope skyward , forever changing human perception of our place in the cosmos . Many of today 's hobby telescopes are much stronger than his , so anyone can easily follow in his footsteps and cast the same gaze . And many did , when the three moons passed , posting their recordings of the triple moon transit on YouTube . The moons spin around Jupiter at different speeds ; their orbits vary in duration from two to 17 days , so having them line up together to zip across the side of Jupiter pointed our way is special . Io , Europa , and Callisto put on the show without Ganymede , which was too far off to the side to make it into the group photo . Europa is in the spotlight of space explorers , because they think there may be life in the fluid water underneath its surface of solid ice . If it is found there , this would be the first discovery of life in our solar system aside from that on Earth .
Three of Jupiter 's four great moons crossed its sunny side in January . That 's rare ; it has happened only twice in the last 15 years . Hubble 's images are primarily for aesthetic purposes , a gift to the public .