Gamma Leonis
Encyclopedia
Gamma Leonis is a binary star system in the constellation
Leo
. It has the traditional name Algieba or Al Gieba.
الجبهة Al-Jabhah, meaning the forehead. Despite this meaning, the star actually appears in the mane of Leo. The star's Latin
name is Juba.
It is known as 軒轅十二 (the Twelfth Star of Xuanyuan) in Chinese. Xuanyuan is the name of Yellow Emperor
.
of +2.28 and is of spectral class
K1-IIIbCN-0.5. The giant K star has a surface temperature of 4,470 K
, a luminosity
180 times that of Earth
's Sun
, and a diameter 23 times that of the Sun. The companion star has an apparent magnitude of +3.51 and belongs to the spectral class G7IIICN-I. The giant G star has a temperature of 4,980 K, a luminosity of 50 times that of the Sun, and a diameter 10 times that of the Sun. With angular separation of just over 4", the two stars are at least 170 AU
apart (four times the distance between Pluto
and the Sun), and have an orbital period of over 500 years. Because the orbital period is so long, only a fraction of the full path has been observed since discovery.
Both stars are almost certainly true giants, meaning that they have stopped fusing
hydrogen
to helium
in their cores and have expanded to great proportions. Although there has been too little observation of their orbit
to calculate their masses, comparison with evolutionary calculations suggests that each are about double the mass of the Sun. Originating from the same interstellar cloud some two billion years ago, the stars have iron
contents about a third that of the Sun. It is hard to tell how far along they might be in their life cycle. They both may be fusing helium in their cores, or they could be giants in development, with quiet helium cores that are waiting to fire up. The chemical composition at the surface, which is influenced by age, suggests the former.
measurements suggest two additional periodicities of 8.5 and 1340 days. The former is likely due to stellar pulsation, whereas the latter could be indicative of the presence of an additional planetary companion with 2.14 Jupiter masses, moderate eccentricity (e=0.13) and located at 2.6 Astronomical Units away from the giant star. Nevertheless the nature of such a signal is still unclear and further investigations are needed to confirm or rule out an additional substellar companion.
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....
Leo
Leo (constellation)
Leo is one of the constellations of the zodiac. Its name is Latin for lion. Its symbol is . Leo lies between dim Cancer to the west and Virgo to the east.-Stars:...
. It has the traditional name Algieba or Al Gieba.
Name origin and history
The name Algieba originates from the ArabicArabic language
Arabic is a name applied to the descendants of the Classical Arabic language of the 6th century AD, used most prominently in the Quran, the Islamic Holy Book...
الجبهة Al-Jabhah, meaning the forehead. Despite this meaning, the star actually appears in the mane of Leo. The star's Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
name is Juba.
- Algieba (gamma), Adhafera (Zeta LeonisZeta LeonisZeta Leonis is a fourth-magnitude star in the constellation Leo. It has the traditional name Adhafera , from the Arabic الضفيرة al-ðafīrah "the braid/curl", a reference clearly to its position in the lion's mane.- Properties :Adhafera is a rare F Class giant star with stellar classification F0III...
), and Al Jabbah (Eta LeonisEta LeonisEta Leonis is a fourth-magnitude star in the constellation Leo.- Properties :Eta Leonis is a white supergiant with the stellar classification A0Ib. Though its apparent magnitude is 3.51, making it a relatively dim star to the naked eye, it is 5,600 times more luminous than the Sun, with an...
) have collectively been called the Sickle. - Algieba (gamma), along with Adhafera (zeta), RegulusRegulusRegulus is the brightest star in the constellation Leo and one of the brightest stars in the night sky, lying approximately 77.5 light years from Earth. Regulus is a multiple star system composed of four stars which are organized into two pairs...
(Alpha) and eta (Al Jabbah) are the 8th manzil, Al Jabhah, the "Forehead," promoting love, benevolence, and help against enemies. - The Lion is associated with the HebrewHebrew alphabetThe Hebrew alphabet , known variously by scholars as the Jewish script, square script, block script, or more historically, the Assyrian script, is used in the writing of the Hebrew language, as well as other Jewish languages, most notably Yiddish, Ladino, and Judeo-Arabic. There have been two...
letter KaphKaphKaph is the eleventh letter of many Semitic abjads, including Phoenician, Aramaic, Hebrew Kaf , Arabic alphabet , Persian alphabet...
and the 11th TarotTarotThe tarot |trionfi]] and later as tarocchi, tarock, and others) is a pack of cards , used from the mid-15th century in various parts of Europe to play a group of card games such as Italian tarocchini and French tarot...
Trump "Strength".
It is known as 軒轅十二 (the Twelfth Star of Xuanyuan) in Chinese. Xuanyuan is the name of Yellow Emperor
Yellow Emperor
The Yellow Emperor or Huangdi1 is a legendary Chinese sovereign and culture hero, included among the Three Sovereigns and Five Emperors. Tradition holds that he reigned from 2697–2597 or 2696–2598 BC...
.
System components
Algieba, as a binary system, consists of two stars. The brighter component has an apparent magnitudeApparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
of +2.28 and is of spectral class
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...
K1-IIIbCN-0.5. The giant K star has a surface temperature of 4,470 K
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
, a luminosity
Luminosity
Luminosity is a measurement of brightness.-In photometry and color imaging:In photometry, luminosity is sometimes incorrectly used to refer to luminance, which is the density of luminous intensity in a given direction. The SI unit for luminance is candela per square metre.The luminosity function...
180 times that of Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
's 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 a diameter 23 times that of the Sun. The companion star has an apparent magnitude of +3.51 and belongs to the spectral class G7IIICN-I. The giant G star has a temperature of 4,980 K, a luminosity of 50 times that of the Sun, and a diameter 10 times that of the Sun. With angular separation of just over 4", the two stars are at least 170 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
apart (four times the distance between Pluto
Pluto
Pluto, formal designation 134340 Pluto, is the second-most-massive known dwarf planet in the Solar System and the tenth-most-massive body observed directly orbiting the Sun...
and the Sun), and have an orbital period of over 500 years. Because the orbital period is so long, only a fraction of the full path has been observed since discovery.
Both stars are almost certainly true giants, meaning that they have stopped fusing
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...
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...
to helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...
in their cores and have expanded to great proportions. Although there has been too little observation of their orbit
Orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
to calculate their masses, comparison with evolutionary calculations suggests that each are about double the mass of the Sun. Originating from the same interstellar cloud some two billion years ago, the stars have iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
contents about a third that of the Sun. It is hard to tell how far along they might be in their life cycle. They both may be fusing helium in their cores, or they could be giants in development, with quiet helium cores that are waiting to fire up. The chemical composition at the surface, which is influenced by age, suggests the former.
Sky appearance
The bright binary system in Leo with orange-red and yellow or greenish-yellow components is visible through a modest telescope under good atmospheric conditions. To the naked eye, the Algieba system shines at mid-second magnitude, but a telescope easily splits the pair.Planetary system
On November 6, 2009, the discovery of a planetary companion around primary star Gamma-1 Leonis was announced. The radial velocityRadial velocity
Radial velocity is the velocity of an object in the direction of the line of sight . In astronomy, radial velocity most commonly refers to the spectroscopic radial velocity...
measurements suggest two additional periodicities of 8.5 and 1340 days. The former is likely due to stellar pulsation, whereas the latter could be indicative of the presence of an additional planetary companion with 2.14 Jupiter masses, moderate eccentricity (e=0.13) and located at 2.6 Astronomical Units away from the giant star. Nevertheless the nature of such a signal is still unclear and further investigations are needed to confirm or rule out an additional substellar companion.
External links
- Jim Kaler's Stars:Algieba
- Astronomical Reference from Author David Darling