NGC 2293

Lore & Background

NGC 2293 is a lenticular galaxy that shows hints of a spiral structure, and its old stars give it an orange color. It lies 0.8 arcminutes from NGC 2292, and both galaxies appear to share a common envelope. A complete ring of neutral hydrogen gas (HI) encircles both galaxies, with a color change in the southwestern part of the ring attributed to star formation. There is a marked absence of HI near the centers of the two galaxies. The ring may result from an ongoing merger that would produce a giant elliptical galaxy. The most likely model for the ring's formation involves a collision between one of the two galaxies and another galaxy that swept gas away, with the star formation region created by a density wave or stripped by the intruder. It has not been ruled out that the positioning is a projection effect of two galaxies separated by a few million light years. Far infrared observations reveal extensive cold dust at the pair with a temperature of 13 K, lower than dust temperatures in spiral and interacting galaxies, though not of primordial origin. NGC 2292/2293 belongs to the galaxy group LGG 138, which also includes NGC 2280, NGC 2295, ESO 490−G010, and ESO 490−G045.

Reader's Guide

NGC 2293 is significant as part of a galaxy pair that exhibits a rare complete ring of neutral hydrogen gas, a structure that provides insight into galactic interactions and merger processes. The ring's star-forming region and the absence of HI near the galactic centers suggest ongoing dynamical evolution, possibly leading to a giant elliptical galaxy. The cold dust temperature of 13 K, lower than typical for interacting systems, indicates a distinct thermal environment. The pair's membership in LGG 138 places it within a small group of galaxies, offering context for studying group dynamics. The resemblance to carved pumpkins, due to the orange color and bright centers, makes it a visually distinctive object. The uncertainty about whether the ring is a true physical structure or a projection effect underscores the complexity of interpreting such systems. Overall, NGC 2293 contributes to understanding galaxy mergers, HI ring formation, and the properties of cold dust in interacting galaxies.

Did You Know?

• NGC 2293 was discovered by John Herschel on January 20, 1835.
• The galaxy has an orange color due to its old stars, and its bright center gives it a Halloween pumpkin-like appearance.
• A complete ring of neutral hydrogen gas encircles both NGC 2293 and its companion NGC 2292.
• The pair belongs to the galaxy group LGG 138, which includes the spiral galaxy NGC 2280.