Knowra Galactic bar Galactic bar A galactic bar is an elongated arrangement of stars and gas crossing the center of a barred spiral galaxy. Its rotating gravitational structure can redirect gas and shape the galaxy’s evolution.
Stellar orbit : The path a star follows under gravity through space. Many stars in a bar occupy elongated orbits aligned with its rotating structure.
Spiral galaxy : A galaxy with a flattened rotating disk, spiral arms, and a central concentration of stars. Galactic bars are central structures found in a substantial fraction of spiral galaxies.
Barred spiral galaxy : A spiral galaxy whose central region contains a prominent elongated stellar bar. This galaxy class is defined by the presence of a galactic bar.
Spiral arm : A curved, relatively dense pattern of stars, gas, and dust winding through a disk galaxy. Unlike a bar, a spiral arm winds around the disk rather than crossing the center as an elongated structure.
Resonance (celestial mechanics) : A gravitational condition in which orbiting bodies’ frequencies have a simple ratio. Orbital resonances help define the bar’s structure and influence stars and gas around it.
Galactic disk : A flattened, rotating component of a galaxy containing stars, gas, and dust. The bar forms from disk material and lies within the disk’s plane.
Dust lane : A narrow feature of obscuring interstellar dust visible against brighter background light. Prominent dust lanes often trace shocks and gas flows along a bar.
Ring galaxy : A galaxy whose stars and gas form a prominent ring around its center. A ring is a distinct large-scale morphology, though bars can help create rings at resonances.
Angular momentum transport : The redistribution of angular momentum among parts of a physical system. Bars transfer angular momentum outward as they drive gas inward.
Galactic bulge : A dense, roughly spheroidal concentration of stars near a galaxy’s center. A bar may coexist with a bulge and can help build a central boxy structure.
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