Which feature is characteristic of a barred spiral galaxy?

A barred spiral galaxy is specifically defined by its unique structure, which includes spiral arms that originate from an elongated, bar-shaped feature at its center. This bar is typically composed of stars and effectively stretches across the nucleus of the galaxy, influencing the movement and distribution of stars and gas within the galaxy.

The presence of this bar is what distinguishes barred spirals from ordinary spiral galaxies, where the spiral arms radiate symmetrically from a circular nucleus. In a barred spiral, the arms extend from the ends of the bar rather than from a central circular mass. The dynamics and gravitational interactions within these galaxies create distinctive patterns, making the bar a vital characteristic of their structure.

In contrast, spiral galaxies lack this elongated feature in the nucleus, while galaxies with no spiral structure possess a different morphologies altogether. Lastly, a completely round galaxy devoid of distinct features refers to elliptical galaxies, which have a different formation and evolution history compared to barred spirals. Thus, the unique arrangement of a bar-shaped nucleus with spiral arms emanating from it is what makes the identification of barred spiral galaxies distinctively clear.