The Sextans Dwarf Spheroidal is a

dwarf spheroidal galaxy A dwarf spheroidal galaxy (dSph) is a term in astronomy applied to small, low-luminosity galaxies with very little dust and an older stellar population. They are found in the Local Group as companions to the Milky Way and as systems that are c ...

that was discovered in 1990 by

Mike Irwin Michael J. Irwin is a British astronomer. He is the director of the Cambridge Astronomical Survey Unit and one of the discoverers of the Cetus Dwarf galaxy and the Sagittarius Dwarf Elliptical Galaxy. Research Irwin is known worldwide for ...

as the 8th satellite of the

Milky Way The Milky Way or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the #Appearance, galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galax ...

, located in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

Sextans Sextans is a faint, minor constellation on the celestial equator which was introduced in 1687 by Polish astronomer Johannes Hevelius. Its name is Latin for the astronomical sextant, an instrument that Hevelius made frequent use of in his obs ...

. It is also an

elliptical galaxy An elliptical galaxy is a type of galaxy with an approximately ellipsoidal shape and a smooth, nearly featureless image. They are one of the three main galaxy morphological classification, classes of galaxy described by Edwin Hubble in his Hub ...

, and displays a

redshift In physics, a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light). The opposite change, a decrease in wavelength and increase in frequency and e ...

because it is receding from the Sun at 224 km/s (72 km/s from the Galaxy). The distance to the galaxy is 320,000 light-years and the diameter is 8,400 light-years along its major axis. Like other dwarf spheroidal galaxies, the Sextans Dwarf's population consists of old,

metal-poor In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal currently detectable (i.e. non-dark) matter in the universe is either hydrogen or helium, and astronomers ...

stars: one study found that the majority of stars have a metallicity between e/H= −3.2 and −1.4. An analysis of several stars found them to also be deficient in

barium Barium is a chemical element; it has symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element. Th ...

, except for one star.

References

{{DEFAULTSORT:Galaxy, Sextans Dwarf Spheroidal Dwarf spheroidal galaxies Local Group Milky Way Subgroup Sextans ?