When you buy through links on our articles, Future and its syndication partners may earn a commission. A mosaic of the 378 satellite galaxies seen in the survey. | Credit: Yao-Yuan Mao (University of Utah)/DESI Legacy Surveys Sky ViewerThe Milky Way’s system of small, orbiting satellite galaxies is quite unusual, a new 12-year study of other galaxies in the local universe has found.The Satellites Around Galactic Analogs (SAGA) survey is being conducted by a small group of astronomers to learn how the Milky Way and its little retinue of dwarf satellite galaxies compares to other galaxy systems.”The Milky Way’s satellite population is a unique combination of small satellites containing only older stars, and its two largest satellites, which are actively forming new stars,” says Marla Geha, who is a professor of astronomy and physics at Yale University and co-founder of SAGA, in a statement. six small square magnifying stellar objects follow lines to dots on an image of stars and galaxies.Those two largest satellites are the Large and Small Magellanic Clouds, known as the LMC and SMC in shorthand. These two satellites are far and away the largest in the Milky Way’s family and are readily visible to the naked eye from the Southern Hemisphere. Most of the other 59 known satellite galaxies of the Milky Way are exceedingly faint, requiring the Hubble Space Telescope or large ground-based telescopes to detect them.Related: Milky Way galaxy: Everything you need to know about our cosmic neighborhoodSAGA conducted a census of 101 galaxies similar in size and mass to our Milky Way, playing host to 378 satellite galaxies in total. The number of visible satellite galaxies per host galaxy ranged from 0 to 13. This is compared to the Milky Way, where SAGA (using data from the Dark Energy Spectroscopic Instrument, DESI) on the Mayall Telescope at Kitt Peak National Observatory in Arizona could detect only four satellites. The rest of our galaxy’s satellites are simply too faint for DESI to see.”The Milky Way appears to host fewer satellites if you consider the existence of the LMC,” said Yao-Yuan Mao, of the University of Utah and also a SAGA co-founder, in a statement.That’s because the trend discovered by SAGA is for host galaxies to feature more satellite galaxies in general if they also have at least one Magellanic-type galaxy orbiting them.However, galaxies without Magellanic-types do tend to have fewer satellites. One explanation is that the Magellanic Clouds are recent additions to the Milky Way’s family. For example, research back in 2007 by Gurtina Besla, now at Steward Observatory in Arizona, found that the Magellanic Clouds are first-time visitors, snagged by our Milky Way’s gravity in the last three billion years and trapped in orbit. So before the Magellanic Clouds arrived, the Milky Way wouldn’t have been expected to have many bright satellite g …
