Alpha Fornacis (α Fornacis, abbreviated Alpha For, α For) is a
binary star[ system in the southern constellation of ]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 ...
. It is the brightest star in the constellation and the only one brighter than magnitude 4.0. Based on parallax measurements obtained during the Hipparcos mission, it is approximately 46 light-years (14 parsec
The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (au), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, an ...
s) distant from the Sun
The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
.
Its two components are designated Alpha Fornacis A (officially named Dalim )
Nomenclature
''α Fornacis'' ( Latinised to ''Alpha Fornacis'') is the system's Bayer designation. The designations of the two components as ''Alpha Fornacis A'' and ''B'' derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems
A star system or stellar system is a small number of stars that orbit each other, bound by gravitational attraction. A large group of stars bound by gravitation is generally called a '' star cluster'' or '' galaxy'', although, broadly speak ...
, and adopted by the International Astronomical Union
The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreac ...
(IAU).Fomalhaut
Fomalhaut is the brightest star in the southern constellation of Piscis Austrinus, the "Southern Fish", and one of the brightest stars in the night sky. It has the Bayer designation Alpha Piscis Austrini, which is Latinized from ...
ظَلِيم ''al-ẓalīm'', a local word for 'ostrich'. Later, Arabian astronomer would transfer the appellation to Theta Eridani
Theta Eridani, Latinized from θ Eridani, is a binary system in the constellation of Eridanus with a combined apparent magnitude of 2.88. Its two components are designated θ1 Eridani, formally named Acamar (the traditional name of th ...
, as they could not see those other stars from their location.Giuseppe Piazzi
Giuseppe Piazzi ( , ; 16 July 1746 – 22 July 1826) was an Italian Catholic priest of the Theatine order, mathematician, and astronomer. He established an observatory at Palermo, now the '' Osservatorio Astronomico di Palermo – Giuseppe S ...
applied it with the spelling ''Dalim'' to his "III 13" (= α For) in his '' Palermo Catalogue'', and Elijah Burritt labeled it ''Fornacis'' in his Atlas
An atlas is a collection of maps; it is typically a bundle of maps of Earth or of a region of Earth.
Atlases have traditionally been bound into book form, but today many atlases are in multimedia formats. In addition to presenting geograp ...
.[ plate III.]
In 2016, the IAU organized a Working Group on Star Names
The International Astronomical Union (IAU) established a Working Group on Star Names (WGSN) in May 2016 to catalog and standardize proper names for stars for the international astronomical community. It operates under Division C – Education ...
(WGSN)
Properties
Alpha Fornacis has a high proper motion[ and the system displays an excess of infrared emission, which may indicate the presence of circumstellar material such as a ]debris disk
A debris disk (American English), or debris disc (Commonwealth English), is a circumstellar disk of dust and debris in orbit around a star. Sometimes these disks contain prominent rings, as seen in the image of Fomalhaut on the right. Debris di ...
.[ The space velocity components of this star are (U, V, W) = (−35, +20, +30) km/s.][ Approximately 350,000 years ago, Alpha Fornacis experienced a close encounter with the ]A-type main-sequence star
An A-type main-sequence star (A V) or A dwarf star is a main-sequence (hydrogen-burning) star of spectral type A and luminosity class V (five). These stars have spectra defined by strong hydrogen Balmer absorption lines. They measure between ...
Nu Horologii. The two came within an estimated of each other, and both stars have debris disks.[
Alpha Fornacis A has a stellar classification of F8IV, where the luminosity class IV indicates this is a ]subgiant
A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as giant stars. The term subgiant is applied both to a particular spectral luminosity class and to a stage in the evolution ...
star that has just evolved off the main sequence.[ It has 33% more mass than the Sun and is an estimated 2.9 billion years old.][
The secondary, Alpha Fornacis B, has been identified as a ]blue straggler
A blue straggler is a main-sequence star in an open or globular cluster that is more luminous and bluer than stars at the main sequence turnoff point for the cluster. Blue stragglers were first discovered by Allan Sandage in 1953 while perform ...
, and has either accumulated material from, or merged with, a third star in the past. It is a strong source of X-rays and is 78% as massive as the Sun.[
]
References
External links
α For (Dalim)
SKY-MAP.ORG
LHL Digital Collections
Linda Hall library
{{DEFAULTSORT:Alpha Fornacis
F-type subgiants
Fornacis, Alpha
Blue stragglers
Binary stars
Fornax (constellation)
Fornacis, Alpha
CD−29 1177
Circumstellar disks
Eridani, 12
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014879
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Dalim
J03120443-2859156