Spiral from the side

What kind of astronomical object is this? It doesn’t look quite like the kinds of galaxies, nebulae, star clusters or galaxy clusters which Hubble normally brings us images of. In fact, this is a spiral galaxy, named UGC 10043 — we just happen to be seeing it directly from the side! Located roughly 150 million light-years from Earth in the constellation Serpens, UGC 10043 is one of the somewhat rare spiral galaxies that are seen edge-on.

From this point of view, we see the galaxy’s disc as a sharp line through space, overlain with a prominent dust lane. This dust is spread across the spiral arms of UGC 10043, but it looks very thick and cloudy when viewed from the side. You can even see the lights of some active star-forming regions in the arms, shining out from behind the dust. Strikingly, we can also see that the centre of the galaxy sports a glowing, almost egg-shaped ‘bulge’, rising far above and below the disc. All spiral galaxies have a bulge like this one as part of their structure, containing stars that orbit the galactic centre on paths above and below the whirling disc; it’s a feature that isn’t normally obvious in pictures of galaxies. The unusually large size of this bulge compared to the galaxy’s disc is possibly thanks to UGC 10043 siphoning material from a nearby dwarf galaxy. This may also be why the disc is warped, bending up at one end and down at the other.

Like most of the full-colour Hubble images released by ESA/Hubble, this image is a composite, made up of several individual snapshots taken by Hubble at different times and capturing different wavelengths of light. You can see the exact images used in the sidebar on this page. A notable aspect of this image is that the two sets of Hubble data used were collected 23 years apart, in 2000 and 2023! Hubble’s longevity doesn’t just afford us the ability to produce new and better images of old targets; it also provides a long-term archive of data which only becomes more and more useful to astronomers.

[Image Description: A spiral galaxy seen directly from the side, such that its disc looks like a narrow diagonal band across the image. A band of dark dust covers the disc in the centre most of the way out to the ends, and the disc glows around that. In the centre a whitish circle of light bulges out above and below the disc. The tips of the disc are a bit bent. The background is black and mostly empty.]