Free Astronomy Magazine July-August 2025

41 ASTRO PUBLISHING From this vantage point, intricate clumps and strands of dust stand out against the brilliant white galactic nucleus and bulge, creating an effect not unlike Saturn and its rings — but on an epic galactic scale. At the same time, this extreme angle makes it difficult to discern the struc- ture of the Sombrero Galaxy. It’s not clear whether it’s a spiral galaxy, like our own Milky Way, or an elliptical galaxy. Curiously, the galaxy’s disc seems like a fairly typical disc for a spiral galaxy, and its spheroidal bulge and halo seem fairly typical for an el- liptical galaxy — but the combination of the two components resembles neither a spiral nor an elliptical gal- axy. Researchers have used Hubble to investigate the Sombrero Galaxy, measuring the amount of metals (what astronomers call elements heavier than helium) in stars in the galaxy’s expansive halo. This type of measurement can illuminate a gal- axy’s history, potentially revealing whether it has merged with other galaxies in the past. In the case of the Sombrero Galaxy, extremely metal- rich stars in the halo point to a possi- ble merger with a massive galaxy several billion years ago. An ancient galactic clash, hinted at by Hubble’s sensitive measurements, could ex- plain the Sombrero Galaxy’s distinc- tive appearance. JULY-AUGUST 2025 ! L ocated around 30 million light-years away in the constellation Virgo, the Som- brero Galaxy is instantly recognisable. Viewed nearly edge on, the galaxy’s softly luminous bulge and sharply outlined disc resemble the rounded crown and broad brim of the Mexican hat from which the galaxy gets its name. The galaxy is too faint to be spotted with unaided vision, but it is readily viewable with a mod- est amateur telescope. [ESA/Hubble & NASA, K. Noll]