Acamar (pronounced AY-kuh-mar) is found in the constellation Eridanus. It is one of the brightest stars in the constellation Eridanus. The Acamar star, also known as Theta Eridani ( Eri Eridani) is a double star, consisting of an A4 sub-giant and an Al dwarf. The two can be described as the gems in the sky due to their brilliance. Although both were born as white dwarfs, the A4 has since become a sub-giant. The A4 sub-giant will however return to its dwarf status shortly before the end of its life. Figure 1 shows the Acamar.
Fig 1 The Acamar star from Sky-Map
Origin of the Name
According to Richard Allen, the constellation Eridanus derives it name from a folklore about the river Padus or Po in which Phaeton fell when Jupiter slew him with a thunderbolt. This was a punishment for setting the world on fire by misguiding the chariot of Phoebus, his father. Allen reports that Eridanus represents the river Padus (219). Acamar, which means end of the river, was called Achernar in the classical times. Achernar is derived from the Arabic word Al Ahir Al Nahr. This name was given because this star was the very visible at the end of the river Eridanus (298). Achernar is now used to refer to alpha Eridanus. Acamar is a double star with an apparent magnitude of 3.24 for the A4 and a combined apparent magnitude of 2.88 (Sky-Map). The attractive pair of stars appears to be close to each other as seen from the earth (Burnham 889).
Properties of Acamar
Burnham reports that the star has a Right Ascension of 02h58m15.70s and a Declination of -40 o1817.0 (889). The main star, a sub-giant called A4 is white and hotter than the sun. The giant and dwarf stars are separated by an 8.31 arc seconds. The dwarf is also hotter than the sun but with a lower luminosity as compared to A4. Acamar has a parallax of 28.00 (11.00) mas. Figure 2 shows the position of Acamar in the Eridanus constellation.
Other Properties of Acamar are as shown in the tables below
Proper motion (J2000)Right Ascension -0.045 arcsecaDeclination 0.019 arcsecaRadial velocity12 kmsTrigonometric parallax0.035 arcsecGalactic coordinates. (B1950)Longitude 247.5Latitude -60.4GCI unit vector (J2000)X 0.43325Y 0.35145Z -0.46853Separation between the brightest and the second brightest component8.3 arcsecDifference in magnitude between the brightest and second brightest component1.1Rotational Velocity74 kms
ComponentMagnitudeSpectral classCatalogue(s)Name(s)A3.24A2Acamar, q1Eridani, HR 897, HD 18622, SAO 216113B4.35A2q2Eridani, HR 898, HD 18623, SAO 216114 Tables Properties of Acamar from Hoffleit and Warren v.50.
According to Lang (28) one parsec 3.261633 light years and Acamar is 50 parsecs from the sun. That converts to about 150 lights years away from earth. The luminosities of the A4 and A1 Acamar stars are 50 and 20 suns respectively. The radial velocity of the giant star is about 7 miles per second which is faster than the dwarf motion at 12 miles per second (Burnham 1978).
Acamars Life Cycle
Acamars life cycle, like that of any other star, depends on the rate at which it burns hydrogen in its core (Hoffleit and Warren 50). According to Kaler the A4 sub-giant, which is 2.6 times heavier than the sun, is burning on a dead helium core and is expanding to a red giant hood. The A1, which is 2.4 times the mass of the sun, is in a stable hydrogen fusion stage but will inevitably follow the A4.
He notes that the difference in mass gives the A1 a longer life. He further notes that the two of them will retire as dead high density stars that will have shrunk to about the size of the earth.
As stars burn, helium accumulates in the core of the stars causing an increase in the rate of fusion as well as the rate of gravitational self-compressional rates. This speeds up the consumption of the hydrogen supply, which is the source of fuel for the stars, causing them to cool down. The increased gravitation leads to the shrinking of the stars.
The Binary Period
The Binary Period is the time taken by binary stars to revolve around each other. The two stars revolve around each other because of the gravitational force that occurs between them. The force holds them together preventing them from escaping each other.
Energy Generation by Acamar
The Carbon-Nitrogen-Oxygen Pathway is used by Acamar to generate energy (North 609). Energy generation occur in a 6 step sequence whereby 4 hydrogen protons are converted into one helium proton with positrons, neutrinos and some high energy level gamma rays. The energy is therefore in the gamma rays and particles produced in this process as shown in figure 3.
Acamar is no doubt a brilliant double star and is easily visible from earth without visual aids. The star, also referred to as Theta Eri, is found at the south east side of Eridanus. Its position makes it possible to see it from the Southern Hemisphere.
The Acamar is as binary meaning it is comprised of two stars, the larger A4 and the lesser A1. Both of the stars are however larger and massive than the sun.
The knowledge of this star and others in the constellation Eridanus provides a better understanding on the formation and the life cycle of stars. The Acamar also provides information on the existence and life cycle of the binary stars.
Fig 1 The Acamar star from Sky-Map
Origin of the Name
According to Richard Allen, the constellation Eridanus derives it name from a folklore about the river Padus or Po in which Phaeton fell when Jupiter slew him with a thunderbolt. This was a punishment for setting the world on fire by misguiding the chariot of Phoebus, his father. Allen reports that Eridanus represents the river Padus (219). Acamar, which means end of the river, was called Achernar in the classical times. Achernar is derived from the Arabic word Al Ahir Al Nahr. This name was given because this star was the very visible at the end of the river Eridanus (298). Achernar is now used to refer to alpha Eridanus. Acamar is a double star with an apparent magnitude of 3.24 for the A4 and a combined apparent magnitude of 2.88 (Sky-Map). The attractive pair of stars appears to be close to each other as seen from the earth (Burnham 889).
Properties of Acamar
Burnham reports that the star has a Right Ascension of 02h58m15.70s and a Declination of -40 o1817.0 (889). The main star, a sub-giant called A4 is white and hotter than the sun. The giant and dwarf stars are separated by an 8.31 arc seconds. The dwarf is also hotter than the sun but with a lower luminosity as compared to A4. Acamar has a parallax of 28.00 (11.00) mas. Figure 2 shows the position of Acamar in the Eridanus constellation.
Other Properties of Acamar are as shown in the tables below
Proper motion (J2000)Right Ascension -0.045 arcsecaDeclination 0.019 arcsecaRadial velocity12 kmsTrigonometric parallax0.035 arcsecGalactic coordinates. (B1950)Longitude 247.5Latitude -60.4GCI unit vector (J2000)X 0.43325Y 0.35145Z -0.46853Separation between the brightest and the second brightest component8.3 arcsecDifference in magnitude between the brightest and second brightest component1.1Rotational Velocity74 kms
ComponentMagnitudeSpectral classCatalogue(s)Name(s)A3.24A2Acamar, q1Eridani, HR 897, HD 18622, SAO 216113B4.35A2q2Eridani, HR 898, HD 18623, SAO 216114 Tables Properties of Acamar from Hoffleit and Warren v.50.
According to Lang (28) one parsec 3.261633 light years and Acamar is 50 parsecs from the sun. That converts to about 150 lights years away from earth. The luminosities of the A4 and A1 Acamar stars are 50 and 20 suns respectively. The radial velocity of the giant star is about 7 miles per second which is faster than the dwarf motion at 12 miles per second (Burnham 1978).
Acamars Life Cycle
Acamars life cycle, like that of any other star, depends on the rate at which it burns hydrogen in its core (Hoffleit and Warren 50). According to Kaler the A4 sub-giant, which is 2.6 times heavier than the sun, is burning on a dead helium core and is expanding to a red giant hood. The A1, which is 2.4 times the mass of the sun, is in a stable hydrogen fusion stage but will inevitably follow the A4.
He notes that the difference in mass gives the A1 a longer life. He further notes that the two of them will retire as dead high density stars that will have shrunk to about the size of the earth.
As stars burn, helium accumulates in the core of the stars causing an increase in the rate of fusion as well as the rate of gravitational self-compressional rates. This speeds up the consumption of the hydrogen supply, which is the source of fuel for the stars, causing them to cool down. The increased gravitation leads to the shrinking of the stars.
The Binary Period
The Binary Period is the time taken by binary stars to revolve around each other. The two stars revolve around each other because of the gravitational force that occurs between them. The force holds them together preventing them from escaping each other.
Energy Generation by Acamar
The Carbon-Nitrogen-Oxygen Pathway is used by Acamar to generate energy (North 609). Energy generation occur in a 6 step sequence whereby 4 hydrogen protons are converted into one helium proton with positrons, neutrinos and some high energy level gamma rays. The energy is therefore in the gamma rays and particles produced in this process as shown in figure 3.
Acamar is no doubt a brilliant double star and is easily visible from earth without visual aids. The star, also referred to as Theta Eri, is found at the south east side of Eridanus. Its position makes it possible to see it from the Southern Hemisphere.
The Acamar is as binary meaning it is comprised of two stars, the larger A4 and the lesser A1. Both of the stars are however larger and massive than the sun.
The knowledge of this star and others in the constellation Eridanus provides a better understanding on the formation and the life cycle of stars. The Acamar also provides information on the existence and life cycle of the binary stars.
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