A galaxy spinning out of sync
Hubble images reveal NGC 4698, a spiral galaxy 55 million light-years away, whose stars and gas rotate perpendicular to its main disc, defying typical galactic structure.
NGC 4698, a spiral galaxy located approximately 55 million light-years away in the Virgo Cluster, appears serene in a new Hubble Space Telescope image. Despite its calm appearance, the galaxy conceals a significant irregularity in its structure. Unlike most spiral galaxies, NGC 4698 features a galactic bulge that extends outward from its disc at a right angle, a rare characteristic observed in only a few known spiral galaxies.
The galaxy’s central bulge, composed of smaller, older, and cooler stars, surrounds a supermassive black hole millions of times the mass of the Sun. Observations indicate that this black hole is actively growing, pulling in gas from its surroundings. The galaxy’s spiral arms, made of stars, gas, and dust, form a thin disc, while the bulge’s glow is faintly visible above and below the dusty plane in the Hubble image.
Astronomers suggest that the unusual rotation of stars and gas near the galaxy’s centre, which moves perpendicular to the rest of the disc, may result from external influences. The galaxy may have funneled in gas from an outside source, forming a secondary disc at an angle to the main structure. Evidence of a past minor galactic merger is seen in a short ‘tail’ of hydrogen streaming from one side of the galaxy.
The image was created using data from an observing programme (#18103; PI: Thilker) focused on galaxies within the Virgo Cluster. The Hubble image captures the galaxy’s bright central bulge, winding spiral arms, and prominent dust lanes, set against a backdrop of distant stars and faint galaxies.