Tucana Dwarf
Encyclopedia
The Tucana Dwarf Galaxy is a dwarf galaxy
in the constellation
Tucana
. It was discovered in 1990 by R.J. Lavery of Mount Stromlo Observatory
. It is composed of very old stars and is very isolated from other galaxies. Its location on the opposite side of the Milky Way from other Local Group
galaxies makes it an important object for study.
of type dE5. It contains only old stars, formed in a single star formation
era around the time the Milky Way's globular cluster
s formed. It is not experiencing any current star formation, unlike other isolated dwarf galaxies.
The Tucana Dwarf does not contain very much neutral hydrogen
gas. It has a metallicity
of -1.8, a significantly low number. There is no significant spread in metallicity throughout the galaxy. There does not seem to be any substructure to the stellar distribution in the galaxy.
galaxy to most of the other Local Group
galaxies and is therefore important for understanding the kinematics and formation history of the Local Group, as well as the role of environment in determining how dwarf galaxies evolve. It is isolated from other galaxies, and located near the edge of the Local Group.
The Tucana Dwarf galaxy is one of only two dwarf spheroidal galaxies in the Local Group that is not located near the Milky Way or the Andromeda Galaxy
. It is therefore likely to have evolved in isolation for most of its history.
| last1 = van den Bergh
| first1 = Sidney
| authorlink1 = Sidney van den Bergh
| title = Updated Information on the Local Group
| date = April 2000
| journal = The Publications of the Astronomical Society of the Pacific
| volume = 112
| issue = 770
| pages = 529–536
| bibcode = 2000PASP..112..529V
| doi = 10.1086/316548
| postscript =
|arxiv = astro-ph/0001040 }}
}}
Dwarf galaxy
A dwarf galaxy is a small galaxy composed of up to several billion stars, a small number compared to our own Milky Way's 200-400 billion stars...
in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
Tucana
Tucana
Tucana is a constellation in the southern sky, created in the late sixteenth century. Its name is Latin for the toucan, a South American bird.-History:...
. It was discovered in 1990 by R.J. Lavery of Mount Stromlo Observatory
Mount Stromlo Observatory
Mount Stromlo Observatory located just outside of Canberra, Australia, is part of the Research School of Astronomy and Astrophysics at the Australian National University .-History:...
. It is composed of very old stars and is very isolated from other galaxies. Its location on the opposite side of the Milky Way from other Local Group
Local Group
The Local Group is the group of galaxies that includes Earth's galaxy, the Milky Way. The group comprises more than 30 galaxies , with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy...
galaxies makes it an important object for study.
Properties
The Tucana Dwarf is a dwarf spheroidal galaxyDwarf spheroidal galaxy
Dwarf spheroidal galaxy is a term in astronomy applied to low luminosity galaxies that are companions to the Milky Way and to the similar systems that are companions to the Andromeda Galaxy M31...
of type dE5. It contains only old stars, formed in a single star formation
Star formation
Star formation is the process by which dense parts of molecular clouds collapse into a ball of plasma to form a star. As a branch of astronomy star formation includes the study of the interstellar medium and giant molecular clouds as precursors to the star formation process and the study of young...
era around the time the Milky Way's globular cluster
Globular cluster
A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Globular clusters are very tightly bound by gravity, which gives them their spherical shapes and relatively high stellar densities toward their centers. The name of this category of star cluster is...
s formed. It is not experiencing any current star formation, unlike other isolated dwarf galaxies.
The Tucana Dwarf does not contain very much neutral hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
gas. It has a metallicity
Metallicity
In astronomy and physical cosmology, the metallicity of an object is the proportion of its matter made up of chemical elements other than hydrogen and helium...
of -1.8, a significantly low number. There is no significant spread in metallicity throughout the galaxy. There does not seem to be any substructure to the stellar distribution in the galaxy.
Location
The Tucana Dwarf is located in the constellation Tucana. It is about 900 kpc away, on the opposite side of the Milky WayMilky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
galaxy to most of the other Local Group
Local Group
The Local Group is the group of galaxies that includes Earth's galaxy, the Milky Way. The group comprises more than 30 galaxies , with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy...
galaxies and is therefore important for understanding the kinematics and formation history of the Local Group, as well as the role of environment in determining how dwarf galaxies evolve. It is isolated from other galaxies, and located near the edge of the Local Group.
The Tucana Dwarf galaxy is one of only two dwarf spheroidal galaxies in the Local Group that is not located near the Milky Way or the Andromeda Galaxy
Andromeda Galaxy
The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years from Earth in the constellation Andromeda. It is also known as Messier 31, M31, or NGC 224, and is often referred to as the Great Andromeda Nebula in older texts. Andromeda is the nearest spiral galaxy to the...
. It is therefore likely to have evolved in isolation for most of its history.
External links
| last1 = van den Bergh
| first1 = Sidney
| authorlink1 = Sidney van den Bergh
| title = Updated Information on the Local Group
| date = April 2000
| journal = The Publications of the Astronomical Society of the Pacific
| volume = 112
| issue = 770
| pages = 529–536
| bibcode = 2000PASP..112..529V
| doi = 10.1086/316548
| postscript =
|arxiv = astro-ph/0001040 }}
}}