A star forming factory

The celestial object showcased in this week's Hubble Picture of the Week is the spiral galaxy UGC 9684, which lies around 240 million light-years from Earth in the constellation Boötes. This image shows an impressive example of several classic galactic features, including a clear bar in the galaxy's centre, and a halo surrounding its disc.

The impetus for this Hubble image was a study into the host galaxies of Type-II supernovae. These cataclysmic stellar explosions take place throughout the Universe, and are of great interest to astronomers, so automated surveys scan the night sky and attempt to catch sight of them. The supernova which brought UGC 9684 to Hubble's attention occurred during 2020. It has faded from view in this image, which was taken in 2023.

Remarkably, the 2020 supernova in this galaxy isn't the only one that's been seen there — four supernova-like events have been spotted in UGC 9684 since 2006, putting it up there with the most active supernova-producing galaxies. It turns out that UGC 9684 is a quite active star-forming galaxy, calculated as producing one solar mass worth of stars every few years! This level of stellar formation makes UGC 9684 a veritable supernova factory, and a galaxy to watch for astronomers hoping to examine these exceptional events.

[Image Description: A spiral galaxy in the centre of a dark background, surrounded by a few distant galaxies and nearby stars. The galaxy is tilted diagonally and partially towards the viewer. Its disc is cloudy and threaded with dust, without clear arms. A bar of light extends across the disc from the glowing core. A faint halo of gas surrounds the disc.]