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Cursa
Al-Kursi
The chair
كرسي

Beta Eridani (Beta Eri / β Eridani / β Eri) is the second brightest star in the constellation of Eridanus, located in the northeast end of this constellation. It also has the traditional names Cursa and Dhalim.

Theta Eridani (θ Eri / θ Eridani) est une étoile dans la constellation de l'Éridan. Elle est également appelée par son nom traditionnel Acamar (de l'arabe آخر النهر, ʼĀkhir ān-nahr, signifiant « l'embouchure de la rivière » ; avec l'alphabet latin, le « m » peut se confondre avec « rn »). Il est connu comme 天园六 (« la sixième étoile du verger céleste ») en Chine.
Acamar est une étoile double, dont la séparation angulaire des deux étoiles s'élève à 8,2".
Ptolémée l'a décrite comme une étoile de première magnitude ; Al-Soufi l'a classée dans les 30 étoiles les plus brillantes du ciel aux alentours du Xe siècle ; Ulugh Beg l'a également répertoriée comme une étoile de première magnitude au XVe siècle.

Gamma Eridani (γ Eri / γ Eridani) est une étoile de la constellation de l'Éridan. Elle porte également le nom traditionnel Zaurak, qui signifie "le bateau", de l'arabe الزورق Az-Zawraq.
Zaurak a une magnitude apparente de +2,95 et est de type spectral M0.5IIICa-ICr -. Elle est à environ 220 années-lumière de la Terre.

Delta Eridani (δ Eri / δ Eridani) is a 3.54 magnitude star in the constellation of Eridanus. It is also called Rana.
This star is relatively near to the Sun, at a measured distance of about 29 light years. It is sometime listed as a RS Canum Venaticorum-type variable star, but this is likely to be an error. (It is currently a suspected variable.) Rana is a sub-giant star that is near the end of its hydrogen-burning cycle and is now consuming helium. This has caused the star to expand and become hotter than a comparable main sequence star. As a sub-giant star it is subject to pulsations in its atmosphere.
Radial velocity surveys of this star have thus far failed to discern any gas giants in orbit.
The name Rana means "the frog" in Latin, and was apparently transferred in the 20th century from another star, Deneb Kaitos, which was also called "Rana Secunda", or second frog.

Tau4 Eridani (τ4 Eri / τ4 Eri) is a Class M3.5III, fourth-magnitude star in the constellation Eridanus. It has the seldom used proper name Liberfluus (Liberflux), which is Latin and means "Free-flowing" River.
Tau4 Eridani is a binary star system consisting primarily of Class M components, the brightest component being a Class M giant of apparent magnitude 3.66, having a mass and luminosity many times greater than that of the Sun. It is occasionally eclipsed by other stellar components within the system in ways similar to Algol. The entire star system is located about 260 light-years from Earth.

Eta Eridani (η Eri / η Eridani) is a star in the constellation Eridanus. It also has the traditional name Azha ("the breeding place"). The word Azha is a corruption of Persian آشيانه āšiyāne The (ostrich) nest.
Eta Eridani belongs to spectral class K0 and has apparent magnitude +4.1. It is 121 light years from Earth.

Beid
Al-Baid
The eggs
بيض

Omicron-1 Eridani (aka Beid) is a star of visual magnitude 4.04.[1] It lies approximately 125 light-years from Earth in the Eridanus constellation and is a class F (F2) giant with a temperature of 7100 kelvins and a luminosity 28 times that of the Sun. In 1971 it was discovered to be a Delta Scuti variable star, with a variation of just a few hundredths of a magnitude with periods of 1.8 and 3.5 days.

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Alpha Eridani (α Eridani / α Eri) est l'étoile la plus brillante de la constellation de l'Éridan où elle est située à l'extrémité sud. Elle est plus connue sous son nom traditionnel d'Achernar, parfois orthographié Akhenar (de l'arabe آخر النهر Akhir al Nahr, fin de la rivière ; la constellation Éridan représente le fleuve éponyme de la mythologie grecque Éridan). C'est la neuvième étoile la plus brillante du ciel nocturne (voir liste des étoiles les plus brillantes). Du fait de sa déclinaison très basse, elle n'est pas visible depuis l'Europe. Avant que le ciel austral ne soit découvert par les explorateurs européens du XVIe siècle, la constellation de l'Éridan était de fait moins étendue, et c'était à l'époque l'étoile la plus au sud de la partie visible de la constellation d'aujourd'hui qui portait le nom d'Achernar (du fait de l'étymologie du nom, cf ci-dessus). Cette étoile, aujourd'hui θ Eridani est désormais connue sous le nom d'Acamar.
C'est une étoile supergéante très lumineuse de couleur bleue-blanche (température de surface de l'ordre de 20 000 degrés). Sa luminosité totale est plus de 5000 fois supérieure à celle du Soleil, quoique seulement un peu plus de 1000 fois dans le domaine visible, le gros de son énergie étant rayonné dans l'ultraviolet.
Elle montre de faibles mais régulières variations de luminosité qui pourraient être dues à sa rotation rapide (voir ci-dessous) et de la présence de taches à sa surface. Elle présente aussi une perte de masse importante.
Achernar est une des étoiles dont la rotation propre est parmi les plus rapides. La vitesse de sa surface à l'équateur est de 225 kilomètres par seconde, soit 75% de la vitesse critique au-delà de laquelle la matière située à l'équateur serait éjectée par la force centrifuge due à la rotation de l'étoile. Conséquence de cette rotation considérable, Achernar est l'étoile la plus aplatie connue à ce jour. La forme de l'étoile telle qu'elle est observée par le mode interférométrique du Very Large Telescope (VLT) de l'Observatoire Européen Austral (ESO) révèle un ellipsoïde aplati, dont le rapport des axes est de 1,5:1. Ce rapport représente une limite inférieure au rapport entre le diamètre équatorial et de diamètre polaire de l'étoile (si l'axe de rotation de l'étoile n'est pas perpendiculaire à la direction d'observation, ce rapport est plus grand que 1,5). En tout état de cause, cet aplatissement extrême représente un défi pour les modèles de structure interne des étoiles.

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Is a very long, winding river that starts at the left foot of Orion in the north, sweeps south of Taurus, west to the edge of Cetus, then doubles back east to Caelum, and eventually ends far to the south, at the border with Hydrus.
It's difficult now to identify which river the constellation represents. Some writers claimed it was the Tigris or Euphrates, others the Nile. Homer called it an "ocean stream". Since Roman times the river Po was even taken to be the locale.
In fact it may originally have been a mythic river, not meant to be identified with any geographical site.
In any event the story goes that Phaethon, son of Helios the Sun God, pestered his father to allow him to drive the celestial chariot across the skies one day. (The sun was seen as carried daily on a chariot driven by Helios.) Phaethon was encouraged by his sisters and even his own mother. But Helios always refused, knowing that his son was far from ready to assume such an awesome responsibility.
However under the constant pleading by Phaethon, Helios eventually relented. So one day Phaethon climbed into the chariot, drawn by two white horses. He grasped the reins and set off across the skies. But it was soon apparent that Phaethon was incapable of controlling the horses, which galloped so high in the sky that the earth was close to freezing, then plunged so close to the earth that the fields were burnt.
Zeus quickly had enough of this nonsense and sent a thunderbolt, killing the young driver. Phaethon fell into the sacred river Eridanus while his sisters, for having encouraged him in this foolhardy adventure, were changed into poplar trees which stood along its banks.

Eridanus' stars are fairly faint, except for alpha (Achernar, "the end of the river"). This bright star is only visible in latitudes south of 33 degrees, which eliminates most of North America and all of Europe.
Curiously theta Eridani bears nearly the same name, Acamar. This is a variation on Achernar since this star was once the river's terminus and it then bore the name now carried by alpha Eridani.

Double stars:
Theta1 and theta2 Eridani form an attractive pair: 3.4, 4.5; PA 88º, separation 8.2".
Omicron2 Eridani is an interesting triple system only 15.9 light years away.
AB form a very wide pair, with orbit of perhaps 8000-9000 years: 4.5, 9.7; PA 105º, separation 82.8".
BC form a close visual binary with orbit of 252 years. The primary is a white dwarf, with about twice the diameter of the earth. The component a red dwarf.
In fact omicronB is considered the easiest white dwarf for amateur telescopes. The component C has an extremely small mass, considered to be about 0.2 solar mass.
9.7, 10.8; presently PA 337º and 9.3" separation.
32 Eridani is another attractive pair, with colour contrast - yellow and blue: 5.0, 6.3; 347º, 6.9" separation.
32 Eri is near the northern boundary, 10º west of nu Eri (or about 10º north of gamma Eri).
p Eridani is a visual binary near the southern boundary of the constellation. It has an orbit of 483.7 years: 5.8, 5.8; currently the component is at PA 191º and separation 11.5".
The binary is found one degree north of Achernar (alpha Eri).

Variable stars:
Eridanus has a variety of variables, most of which are too small magnitude for amateur observation. Below are only a few examples.
Gamma Eri is an Lb type variable: 2.88-2.96.
Delta Eri is an RS CVn type variable: 3.51-3.56.
Lambda Eri is a beta Cep variable: 4.22-4.34, it has a period of 16h 50m.
Nu Eri is also a beta Cep variable: 3.4-3.6 with period of 4h 16m.

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However under the constant pleading by Phaethon, Apollo eventually allowed the request. So one day Phaethon climbed into the chariot, which was drawn by two white horses, grasped the reins and set off across the skies. It was soon apparent that Phaethon was incapable of controlling the horses, as they galloped so high in the sky that the earth was close to freezing, then they plunged so close to the earth that the fields were burnt. Zeus soon had enough of this nonsense and sent a thunderbolt, killing the young man. His burning body fell to Earth and landed in the River Eridanus. His sisters, for having encouraged him in this foolhardy adventure, were changed into poplar trees which stood along its banks.

It's difficult now to identify which river the constellation represents; some writers claimed it was the Tigris or Euphrates, others the Nile. And Homer called it an "ocean stream". In fact, it may originally have been a mythic river, not meant to be identified with any geographical site. Eridanus might represent the Sumerian Strong River, also known as Ariadan. Or it might be one of more of any other important rivers--the Ganges, Po, Euphrates, or Nile.

The story goes that Phaethon, son of Apollo the Sun God, pestered his father to allow him to drive the celestial chariot across the skies one day. The sun was seen as carried daily on a chariot driven by Apollo. Phaethon was encouraged by his sisters and even his own mother. But Apollo always refused, knowing that his son was far from ready to assume that awesome responsibility.

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Acamar
Theta1 Eridani

Distance (Light Years) 161 ± 4
Visual Magnitude 2.88(Combined)
Constellation Eridanus
Color (B-V) 0.14

Names For This Star

According to Allen, this star, Theta Eridani, was originally recognized as the end of the River Eridanus and therefore bore the name Achernar. This name now applies to Alpha Eridani instead.
According to Allen, the first usage of the name "Acamar" for this star was in the Alfonsine Tables published in Spain in 1252 under the patronage of King Alfonso X of Leon and Castile. However, Allen gives no information about the origin of the name.

Description of the Star

Acamar is a binary star system. The primary, Acamar A, is an A4III normal giant. This star is much hotter than the sun and white in color. Even though the smaller star is technically a dwarf, both stars are larger in mass and radius than our sun.

The smaller star is about one magnitude dimmer than the larger star and lies about 8.31 arc seconds away from it. At the distance of the star system from the earth, this separation corresponds to more than 5 times the diameter of the solar system out to Pluto.
According to Burnham a very slow orbital motion has been observed for the companion relative to the primay. This is consistent with the large separation between the stars.

Achernar
Alpha Eridani

Distance (Light Years) 144 ± 4
Visual Magnitude 0.45
Color (B-V) -0.16

Names For This Star

The name "Achernar" from the Arabic name for this star: Al Ahir al Nahr, which means "the End of the River". The river to which the name refers is of course, the River Eridanus, which is the constellation to which this star belongs.
Description of the Star

Achernar is a very hot B3Vpe main sequence star blue in color, about 9 times the diameter of the sun and much more luminous. According to Burnham, the surface temperature is around 14,000 K. The temperature and diameter of the star imply a luminosity about 1300 times larger than that of the sun.
Spectral emission lines suggest an expanding shell of gas surrounding the star.