The Fornax Dwarf Spheroidal (formerly known as the Fornax System) is an elliptical

dwarf galaxy A dwarf galaxy is a small galaxy composed of about 1000 up to several billion stars, as compared to the Milky Way's 200–400 billion stars. The Large Magellanic Cloud, which closely orbits the Milky Way and contains over 30 billion stars, is so ...

in the constellation

Fornax Fornax () is a constellation in the southern celestial hemisphere, partly ringed by the celestial river Eridanus. Its name is Latin for furnace. It was named by French astronomer Nicolas Louis de Lacaille in 1756. Fornax is one of the 88 modern ...

that was discovered in 1938 by

Harlow Shapley Harlow Shapley (November 2, 1885 – October 20, 1972) was an American scientist, head of the Harvard College Observatory (1921–1952), and political activist during the latter New Deal and Fair Deal. Shapley used Cepheid variable stars to estim ...

. He discovered it while he was in

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bounded to the south by of coastline that stretch along the Atlantic Ocean, South Atlantic and Indian Oceans; to the ...

on photographic plates taken by the 24 inch (61 cm) Bruce refractor at

Boyden Observatory Boyden Observatory is an astronomical research observatory and science education centre located in Maselspoort, north-east of the city of Bloemfontein in Free State, South Africa. The observatory is managed by the Physics Department of the Un ...

, shortly after he discovered the

Sculptor Dwarf Galaxy The Sculptor Dwarf Galaxy (also known as Sculptor Dwarf Elliptical Galaxy or the Sculptor Dwarf Spheroidal Galaxy, and formerly as the Sculptor System) is a dwarf spheroidal galaxy that is a satellite of the Milky Way. The galaxy lies within the ...

. The galaxy is a satellite of the

Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. ...

and contains six

globular cluster A globular cluster is a spheroidal conglomeration of stars. Globular clusters are bound together by gravity, with a higher concentration of stars towards their centers. They can contain anywhere from tens of thousands to many millions of membe ...

s, an unusually high number for its size; the largest, NGC 1049, was discovered before the galaxy itself. The galaxy is also receding from the

at 53 km/s. It mostly contains

population II During 1944, Walter Baade categorized groups of stars within the Milky Way into stellar populations. In the abstract of the article by Baade, he recognizes that Jan Oort originally conceived this type of classification in 1926: Baade noticed ...

stars, but also has populations of young and intermediate age.

Globular clusters

Using the

Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most vers ...

, scientists derived a color-magnitude diagram for Fornax 4, a globular cluster within this galaxy. Unlike the

s Fornax 1, 2, 3, and 5, which have horizontal branches across a wide range of colors and include RR Lyrae variables, Fornax 4 is found to have only red in its horizontal branch. Fornax 4 is also ~3 Gyr younger than the other globular clusters. The color-magnitude diagram of Fornax 4 has a strong similarity to "young" galactic globular Ruprecht 106. It has been debated for some time whether the globular cluster Fornax 6 is a true member of the Fornax Dwarf, or merely a chance alignment of stars and/or galaxies. A 2021 study found it to be a true cluster and a member, but it is notably more

metal-rich In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as ...

and therefore likely younger than the other clusters. It is estimated to be about 2 billion years old. Heic1425a.tif,

image of four of the globular clusters in Fornax Dwarf It is not known why spheroidals allow the formation of globular clusters like Fornax 4 and

Terzan 7 Terzan 7 is a sparse and young globular cluster that is believed to have originated in the Sagittarius Dwarf Spheroidal Galaxy (Sag DEG) and is physically associated with it. It is relatively metal rich with Fe/Hydrogen.html"_;"title="Iro ...

(of Sagittarius dwarf) long after globular clusters ceased to form in the main body of the Galactic halo. Another possibility is that "young" globular clusters of the outer halo like Ruprecht 106 were originally formed in now defunct dwarf spheroidals.

References

External links

*
Fornax dSph

* {{DEFAULTSORT:Fornax Dwarf Dwarf galaxies Dwarf elliptical galaxies Local Group Milky Way Subgroup Fornax (constellation) 10074 ?