Overview

Sextans is a small, faint constellation located along the celestial equator. Its name derives from the sextant, a navigational instrument, and it has no roots in ancient mythology because it was created in the early modern period. Sextans contains no very bright stars and is best known to amateur astronomers for a handful of galaxies and dwarf systems that lie within its boundaries. For general information see Sextans.

Characteristics

The constellation covers a modest area of sky and is bordered by brighter constellations such as Leo to the north and Hydra to the south. Its stars are relatively dim: the brightest, Alpha Sextantis, is of only moderate visual brightness and the pattern is not prominent to the naked eye under typical suburban skies. Because it straddles the celestial equator, Sextans can be observed from both hemispheres at suitable seasons.

History and name

Sextans was introduced in the 17th century by the Polish astronomer Johannes Hevelius, who added several modern constellations based on scientific instruments and everyday objects. Hevelius named this one after the sextant, reflecting the era's interest in navigation and precision instruments rather than classical myth. Unlike ancient constellations, Sextans carries no mythological stories associated with its stars.

Notable objects

Although it contains no Messier objects, Sextans hosts a number of interesting deep-sky targets for telescopes and long-exposure photography:

  • NGC 3115 — a lenticular galaxy sometimes called the Spindle Galaxy, relatively bright for small scopes and a popular target for amateur observers.
  • Sextans A and Sextans B — dwarf irregular galaxies that are studied as examples of small, gas-rich systems in the nearby universe.
  • Sextans Dwarf — a low-surface-brightness dwarf spheroidal galaxy that is a satellite of the Milky Way and of interest in studies of dark matter and galactic evolution.

Observing tips and significance

Sextans is most easily found by locating the brighter neighboring constellation Leo and searching southward for a sparse field of faint stars. It is best observed in late winter and spring months from mid-northern latitudes. While not a dramatic constellation visually, Sextans is valuable to astronomers because it includes nearby dwarf galaxies and a lenticular galaxy that provide insight into galaxy morphology and the structure of the local universe.

Notable facts

As a modern, instrument-themed constellation, Sextans highlights the historical shift in star naming that occurred during the age of exploration and scientific instrumentation. Its inclusion of several dwarf galaxies and a Milky Way satellite makes it disproportionately interesting to professional astronomers compared with its modest naked-eye presence.