Have you ever looked up at the night sky and wondered about the galaxies and stars that twinkle back at you? One of these glittering celestial bodies is the Sagittarius Dwarf Spheroidal Galaxy (Sgr dSph), a tiny galaxy right in our Milky Way’s backyard. But don’t let the word ‘tiny’ fool you, because when it comes to the universe, even the smallest things can be incredibly vast.
The Sagittarius Dwarf Galaxy, discovered in 1994, is about 10,000 light-years in diameter. That’s massive, right? Well, in the grand scheme of things, it’s actually quite small compared to other galaxies! For example, our home galaxy, the Milky Way, spans a whopping 100,000 light-years in diameter. That’s ten times the size of the Sagittarius Dwarf Galaxy!
The Sagittarius Dwarf Galaxy is currently about 70,000 light-years from Earth, orbiting our Milky Way Galaxy. This orbit takes the galaxy over the Milky Way’s galactic poles, about 50,000 light-years from the Milky Way’s core. That’s roughly one third of the distance of the Large Magellanic Cloud, another galaxy near us. In its looping, spiraling path, this little galaxy has passed through the plane of the Milky Way several times in the past. These galactic encounters have caused ripples and perturbations in a set of stars near the Milky Way’s core. These movements were triggered when the Sagittarius Dwarf Galaxy moved past the Milky Way between 300 and 900 million years ago.
Despite its small size, the Sagittarius Dwarf Galaxy is packed with intriguing features. It contains four globular clusters in its main body, with the brightest of them—NGC 6715 (M54)—being known well before the discovery of the galaxy itself. The study of these clusters and their movements has provided astronomers with valuable insights into the history and makeup of our own Milky Way, demonstrating that size doesn’t always equate to significance. In conclusion, the Sagittarius Dwarf Galaxy may be petite when compared to the colossal galaxies that populate our universe, but it’s an integral part of our galactic neighborhood. Its size, orbit, and the fascinating features it houses make it a compelling subject of study, reminding us that the universe is always full of surprises, no matter how big or small!
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