Just as moons surround planets, galaxies too have their group of smaller satellite galaxies circling them. These celestial entities are ubiquitous throughout the cosmos and can often be identified with a mere snapshot.
For instance, consider the Andromeda Galaxy, our Milky Way’s most significant neighbor. Visible in its photographs are two orbiting galaxies, M110 in the lower right, and the glowing orb of M32 situated above the Andromeda's nucleus.
The Milky Way too, is encircled by numerous satellite galaxies. But the question that arises is - how many of these galaxies exist?
Answering this question at present is challenging. Our positioning within our own galaxy obstructs our view of certain sky regions, particularly towards the galactic center. Additionally, some satellite galaxies are diminutive and sparse, making their identification within the surrounding stars quite arduous. To ascertain whether a galaxy truly orbits the Milky Way, its velocity needs to be determined. The Gaia probe's recent findings illustrate that some perceived satellite galaxies are moving too quickly to be in orbit, their proximity to the Milky Way being a mere chance occurrence.
Despite these challenges, we are aware of 69 galaxies situated within 1.4 million light-years from the Milky Way. The status of many as true satellite galaxies remains uncertain.
The most renowned satellite galaxies of our Milky Way are the Large and Small Magellanic Clouds, visible to the naked eye since ancient times. Another galaxy of note is the Sagittarius Elliptical Dwarf Galaxy, 70 thousand light years away from Earth and spanning 10 thousand light years. This petite galaxy hosts four globular clusters, with one intriguingly discovered before the galaxy itself, signifying how these galaxies are faint, sparse and require meticulous analysis for detection.
Credit: Jim Matzger.
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