Sagittarius Dwarf Spheroidal Galaxy

The Sagittarius Dwarf Spheroidal Galaxy is a small satellite of the Milky Way whose stars are being pulled into long tidal streams by the larger galaxy.

Sagittarius Stream: A long stream of stars and gas torn from the Sagittarius Dwarf Spheroidal Galaxy by the Milky Way. This stellar debris is the clearest visible result of the galaxy’s ongoing disruption.
R. Michael Irwin: A British astronomer whose work includes studies of the structure and stellar populations of nearby galaxies. He was part of the team that discovered Sagittarius in 1994.
M54: A massive globular cluster located at the center of the Sagittarius Dwarf Spheroidal Galaxy. Its central position made it a candidate nucleus of Sagittarius, though its relation to the galaxy is complex.
Galactic archaeology: The reconstruction of a galaxy’s formation history from the ages, chemistry, and motions of its stars. Sagittarius’s streams let astronomers trace an accretion event still in progress.
Large Magellanic Cloud: The largest satellite galaxy of the Milky Way, a gas-rich irregular galaxy visible from the Southern Hemisphere. Unlike Sagittarius, it remains a prominent, largely intact satellite.
Tidal stripping: The loss of matter from an object under the differential gravitational pull of a more massive body. It describes how the Milky Way removes stars from Sagittarius.
Alistair R. Conn: An astronomer known for research on Local Group galaxies and their stellar populations. He co-discovered Sagittarius with R. Michael Irwin and colleagues.
Terzan 7: A globular cluster associated with the Sagittarius Dwarf Spheroidal Galaxy. Its stellar population links it to Sagittarius and provides clues to the galaxy’s history.
Milky Way mass: The total mass of the Milky Way, including its stars, gas, and dark matter. Models of Sagittarius’s orbit and stream constrain the Galaxy’s gravitational mass.
Small Magellanic Cloud: A nearby dwarf irregular galaxy that orbits the Milky Way alongside the Large Magellanic Cloud. Its gas-rich irregular structure contrasts with Sagittarius’s spheroidal form and strong tidal disruption.

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