NGC 2775
Unbarred spiral galaxy with a prominent ring and flocculent arms.
NGC 2775, also cataloged as Caldwell 48, is a spiral galaxy situated in the constellation Cancer. It lies about 20.5 megaparsecs from the Milky Way and was first observed by the German-British astronomer William Herschel on December 19, 1783.
Classified as SA(r)ab, this galaxy is unbarred, featuring a prominent ring structure and flocculent, tightly wound spiral arms. It is tilted at a 44-degree angle relative to Earth’s line of sight. Its nucleus is inactive, and the large central bulge—extending to a certain angular radius—contains very little gas. This lack of gas may be due to a high rate of supernovae. While star formation occurs in the dusty outer ring, the galaxy shows no current starburst activity, and the nucleus itself is almost entirely free of star formation.
A hydrogen tail suggests NGC 2775 once interacted with a faint companion. A satellite galaxy appears to have orbited it multiple times, losing mass and leaving behind faint, shell-like structures. The nearby irregular galaxy NGC 2777 has a tidal tail of hydrogen gas pointing back toward NGC 2775, indicating a possible link between the two.
NGC 2775 belongs to the Antlia-Hydra Cluster and is the brightest member of the NGC 2775 Group (also known as LGG 169), a small galaxy group within the Virgo Supercluster—home to the Local Group as well. Other members of this group include NGC 2777 and UGC 4781.
One supernova has been observed in NGC 2775: SN 1993Z, a Type Ia event with a magnitude of 13.9. It was discovered by the Leuschner Observatory Supernova Search on September 23, 1993. By September 25, spectral analysis indicated it had peaked about four weeks earlier.
Quick Facts
- Epoch
- J2000
- Ra
- 09 · 10 · 20.112
- Dec
- +07 · 02 · 16.53
- Constellation Name
- Cancer
- Dist Ly
- 20.5 Mpc
- Z
- 0.004500 · 0.00000334ned
- Appmag V
- 10.4
Facts from the source article.
Lore & Background
NGC 2775 was discovered by German-British astronomer William Herschel on 19 December 1783. It has a morphological classification of SA(r)ab, indicating an unbarred spiral galaxy with a prominent ring structure and flocculent, tightly wound spiral arms. The galaxy is inclined at an angle of 44° to the line of sight from Earth. Its galactic nucleus is not active, and the large nuclear bulge is relatively gas free, possibly due to a high supernova rate. Although star formation occurs in the dusty outer ring, NGC 2775 does not display any current starburst activity, and the galactic nucleus is virtually free of star formation.
The galaxy's hydrogen tail feature suggests a past interaction with a faint companion. A satellite galaxy appears to have orbited NGC 2775 multiple times, losing mass and creating faint, shell-like structures. Nearby irregular galaxy NGC 2777 displays a tidal tail of hydrogen gas that points back to NGC 2775, indicating a possible link between the two. NGC 2775 belongs to the Antlia-Hydra Cluster and is the most prominent member of the NGC 2775 Group (also known as LGG 169), which includes NGC 2777 and UGC 4781.
Reader's Guide
NGC 2775 holds significance as the brightest member of its eponymous galaxy group, which is part of the Virgo Supercluster alongside the Local Group. Its morphological classification as SA(r)ab provides a clear example of an unbarred spiral with a ring and tightly wound arms. The galaxy's relatively gas-free nuclear bulge, possibly linked to a high supernova rate, contrasts with ongoing star formation in its outer dusty ring, yet no starburst activity is present. Evidence of past interactions includes a hydrogen tail and shell-like structures from a satellite galaxy, as well as a tidal tail from NGC 2777 pointing back to NGC 2775. One supernova, SN 1993Z (Type Ia, magnitude 13.9), was observed in NGC 2775, discovered on 23 September 1993 by the Leuschner Observatory Supernova Search; spectral analysis later indicated it had peaked about four weeks earlier. These features make NGC 2775 a valuable object for studying galactic interactions, star formation suppression in bulges, and the dynamics of small galaxy groups.
Did You Know?
- NGC 2775 was discovered by William Herschel on 19 December 1783.
- One supernova, SN 1993Z (Type Ia, mag. 13.9), was observed in NGC 2775.
- The galaxy's hydrogen tail suggests a past interaction with a faint companion.
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