NGC 1357
Farthest known member of the Eridanus Cluster.
NGC 1357 is a spiral galaxy in the constellation Eridanus, located about 92 million light-years away. It belongs to the Eridanus Cluster—a collection of roughly 200 galaxies—and is the most distant known member, lying at the cluster’s far edge. William Herschel discovered it on February 1, 1785.
Classified as Sab under the Hubble scheme, NGC 1357 is an unbarred spiral galaxy. It is receding from the Milky Way at 2,018 km/s. On the night sky, it spans 3.2 by 2.4 arcminutes, corresponding to an actual diameter of about 85,000 light-years.
Its surface brightness profile reveals a small bulge and a large, roughly exponential disk. An automatic bulge-disk fit produces an unreliably large bulge that extends across the entire galaxy. A more accurate fit adds a second exponential disk component in the inner region, which corresponds to tightly wound spiral arms with higher surface brightness. Spectral analysis of NGC 1357 has detected ionized calcium.
Quick Facts
- Epoch
- J2000
- Ra
- 03 · 33.171
- Dec
- -13 · 39
- Dist Ly
- 28.1 Mpc (92 Mly)
- Z
- 2018 ± 9
- Appmag V
- 11.5
- Constellation Name
- Eridanus
- Notes
- Spiral galaxy with gas ring
- Names
- NGC 1357, GSC 05302-00236, LEDA 13166, MCG-02-10-001, 6dFGS gJ033317.1-133951, HIPASS J0333-13, 2MASX J03331709-1339509, [CHM2007] LDC 251 J033317.09-1339509
Facts from the source article.
Lore & Background
NGC 1357 was discovered by William Herschel on February 1, 1785. It is a spiral galaxy with a Hubble classification of Sab, indicating it has no bar. The galaxy is moving away from the Milky Way at a rate of 2,018 km/s. Its apparent size on the night sky is 3.2 arcminutes by 2.4 arcminutes, which corresponds to a real diameter of about 85,000 light years.
The surface brightness profile of NGC 1357 reveals a small bulge and a large, fairly exponential disk. An automatic bulge-disk fit yields an unreliably large bulge extending through the entire galaxy. A more reasonable fit is obtained by adding another exponential disk component to the inner part of the galaxy, which corresponds to the region of tightly wound spiral arms with higher surface brightness.
Analysis of the galaxy's spectra has revealed the presence of ionised calcium.
Reader's Guide
NGC 1357 holds significance as the farthest known member of the Eridanus Cluster, a cluster of about 200 galaxies. Its location at the very edge of the cluster makes it a useful marker for the cluster's spatial extent. The galaxy's surface brightness profile presents a notable challenge in modeling: an automatic bulge-disk fit produces an unreliably large bulge that extends through the whole galaxy, while a more reasonable fit requires the addition of an inner exponential disk component. This inner component corresponds to the region of tightly wound spiral arms with higher surface brightness, indicating a complex structure that may inform studies of spiral galaxy formation and evolution. The detection of ionised calcium in its spectra provides a chemical signature that can be compared with other galaxies. As an isolated spiral galaxy, NGC 1357 offers a relatively undisturbed environment for studying spiral structure and dynamics, free from the gravitational interactions that affect many cluster members. Its discovery by William Herschel in the late 18th century places it among the early cataloged deep-sky objects.
Did You Know?
- The galaxy's spectra revealed the presence of ionised calcium.
- Its surface brightness profile requires an additional inner exponential disk component for a reasonable fit.
More in Galaxy Clusters and Groups, Part 4 1-24
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