Alpha Fornacis
Encyclopedia
Alpha Fornacis (α Fornacis, α For) is the brightest star
in the constellation
Fornax
, its only star brighter than magnitude 4.0. It has the proper names Dalim (in Piazzi
's Palermo Catalogue) and Fornacis (in Burritt's Atlas). This star was formally identical with 12 Eridani
.
The stellar classification
of Alpha Fornacis is F8IV, where the luminosity class IV indicates this is a subgiant 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. Alpha Fornacis is a binary star
and has a high proper motion
. This system displays an excess of infrared
emission, which may indicate the presence of circumstellar material such as a debris disk
.
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 HD 17848. The two came within an estimated 0.265 ly of each other.
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
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....
Fornax
Fornax
Fornax is a constellation in the southern sky. Its name is Latin for furnace. It was created in the 18th century and is now one of the 88 modern constellations.-History:Fornax was formed by Nicolas Louis de Lacaille in 1756...
, its only star brighter than magnitude 4.0. It has the proper names Dalim (in Piazzi
Giuseppe Piazzi
Giuseppe Piazzi was an Italian Catholic priest of the Theatine order, mathematician, and astronomer. He was born in Ponte in Valtellina, and died in Naples. He established an observatory at Palermo, now the Osservatorio Astronomico di Palermo – Giuseppe S...
's Palermo Catalogue) and Fornacis (in Burritt's Atlas). This star was formally identical with 12 Eridani
Eridanus (constellation)
Eridanus is a constellation. It is represented as a river; its name is the Ancient Greek name for the Po River. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations. It is the sixth largest of the modern...
.
The stellar classification
Stellar classification
In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...
of Alpha Fornacis is F8IV, where the luminosity class IV indicates this is a subgiant star that has just evolved off the main sequence
Main sequence
The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell...
. It has 33% more mass than the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
and is an estimated 2.9 billion years old. Alpha Fornacis is a binary star
Binary star
A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...
and has a high proper motion
Proper motion
The proper motion of a star is its angular change in position over time as seen from the center of mass of the solar system. It is measured in seconds of arc per year, arcsec/yr, where 3600 arcseconds equal one degree. This contrasts with radial velocity, which is the time rate of change in...
. This system displays an excess of infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
emission, which may indicate the presence of circumstellar material such as a debris disk
Debris disk
A debris disk 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 disks have been found around both evolved and young stars, as well as at least one debris disk in orbit around a...
.
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 HD 17848. The two came within an estimated 0.265 ly of each other.