An unlikely spiral

This image shows LEDA 42160, a galaxy about 52 million light-years from Earth in the constellation Virgo. The dwarf galaxy is one of many forcing its way through the comparatively dense gas in the Virgo cluster, a massive cluster of galaxies. The pressure exerted by this intergalactic gas, known as ram pressure, has dramatic effects on star formation in LEDA 42160, which are presently being studied using the Hubble Space Telescope.

LEDA 42160 falls into the category of ‘Magellanic spiral galaxy’, or type Sm for short, under the de Vaucouleurs galaxy classification system. Magellanic spiral galaxies can be further sub-categorised as barred (SBm), unbarred (SAm) and weakly barred (SABm), where a ‘bar’ is an elongated bar-shape at a galaxy’s core. Generally speaking, Magellanic spiral galaxies are dwarf galaxies with only one single spiral arm. They are named after their prototype, the Large Magellanic Cloud, which is an SBm galaxy. Magellanic spiral galaxies are an interesting example of how galaxy categorisation is actually more nuanced than simply ‘spiral’, ‘elliptical’ or ‘irregular’. 

[Image Description: A distorted dwarf galaxy, obscured by dust and by bright outbursts caused by star formation, floats roughly in the centre. A few distant galaxies are visible in the background around it, many as little spirals, and also including a prominent elliptical galaxy. A bright star hangs above the galaxy in the foreground, marked by cross-shaped diffraction spikes.]

Links

• Pan of LEDA 42160