This glittering image from the NASA/ESA Hubble Space Telescope shows the spiral galaxy IC 5332. The galaxy lies about 30 million light-years away in the constellation Sculptor and has an almost face-on orientation to Earth. To understand the term “face-on,” it is helpful to visualize a spiral galaxy as an extremely large disk. If the galaxy’s orientation makes it appear circular and disk-shaped from our perspective on Earth, then we say that it is “face-on.”
In contrast, if the galaxy’s orientation is such that it appears squashed and oval-shaped, then we say that it is “edge-on.” The key thing is that the same galaxy would look extremely different from our perspective depending on whether it was face-on or edge-on as seen from Earth.
IC 5332 is an SABc-type galaxy in the De Vaucouleurs system of galaxy classification. The “S” identifies it as a spiral galaxy, which it clearly is, given its well-defined arms of bright stars and darker dust that curl outwards from the galaxy’s dense and bright core.
The “AB” designation is a little more complex. It means that the galaxy is weakly barred, which refers to the shape of the galaxy’s center. The majority of spiral galaxies do not spiral out from a single point, but rather from an elongated bar-type structure. SAB galaxies—which are also known as intermediate spiral galaxies—do not have a clear bar-shape at their core, but also do not spiral out from a single point, instead falling somewhere in between.
The lowercase “c” describes how tightly wound the spiral arms are: “a” would indicate very tightly wound, and “d” very loosely wound. Thus, IC 5332 is an intermediate spiral galaxy on many fronts: weakly barred, with quite loosely wound arms, and almost completely face-on.
Hubble captures spiral galaxy IC 5332 face-on (2023, October 23)
retrieved 26 October 2023
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