Achernar star

Achernar Star: Type, Age, Size, Diameter, Mass, Temperature, Color, Distance

Achernar Star: Type, Age, Size, Diameter, Mass, Temperature, Color and Distance from Earth

Achernar is a fascinating star in the southern sky that has captured the imagination of stargazers and astronomers alike for centuries. Known for its unusual properties, including its rapid rotation and blue color, Achernar has been the subject of much study and research. In this article, we'll explore what makes Achernar so unique, where it is located, and what we know about its properties and characteristics.

What is Achernar?

Achernar is a bright star located in the constellation Eridanus. It is the ninth brightest star in the night sky, and one of the closest stars to Earth. Its name comes from the Arabic phrase for "the end of the river," as it appears at the southern end of the constellation Eridanus, which is often depicted as a river in ancient star maps.

Achernar is a blue-white star that is approximately six times larger than our Sun, and around 40 times more luminous. It is also one of the hottest stars known to science, with surface temperatures that can exceed 10,000 degrees Celsius. Despite its brightness and proximity to Earth, however, Achernar is not visible from most of the northern hemisphere, as it lies too far south to be seen from latitudes above around 33 degrees north.

Achernar star

Properties of Achernar

One of the most interesting features of Achernar is its extremely rapid rotation. In fact, Achernar is one of the fastest-spinning stars known to science, with a rotational velocity at its equator of around 225 kilometers per second. This means that the star's equator is spinning at a speed of around 250 times faster than the rotation of the Earth. As a result of this rapid rotation, the shape of the star is distorted, with its equatorial diameter around 50% larger than its polar diameter.

Another interesting feature of Achernar is its strong stellar wind. As a hot and massive star, Achernar produces a strong stellar wind that blows material away from its surface at speeds of up to 3.5 million kilometers per hour. This stellar wind is thought to be responsible for the creation of a large envelope of gas and dust around the star, known as a circumstellar disk.

Location of Achernar

Achernar is located in the constellation Eridanus, which is one of the largest and longest constellations in the sky. It is located in the southern hemisphere, at a declination of around 57 degrees south, and a right ascension of around 1 hour and 37 minutes. As mentioned earlier, Achernar is not visible from most of the northern hemisphere, as it lies too far south to be seen from latitudes above around 33 degrees north.

Achernar Star Type

Achernar star, officially known as Alpha Eridani, belongs to the category of stars classified as B-type main-sequence stars. This classification provides a glimpse into its fundamental nature and evolutionary stage.

Achernar Star Age

With an estimated age of around 30 million years, Achernar star is relatively young compared to other stellar objects. Its youthful age contributes to its brightness and dynamic behavior, highlighting the energetic processes occurring within its core.

Achernar Star Size

The size of Achernar star, also known as Alpha Eridani, is a captivating feature that draws astronomers and space enthusiasts alike. This luminous B-type main-sequence star boasts an intriguing oblate shape, with noticeable differences between its equatorial and polar diameters due to its rapid rotation. This unique characteristic gives Achernar star a distinct appearance when observed from Earth. As we explore the universe's wonders, delving into the size of Achernar star serves as a reminder of the diverse and captivating nature of celestial objects that grace our night skies.

Achernar Star Diameter

The diameter of Achernar star, also known as Alpha Eridani, holds a compelling allure for astronomers and stargazers alike. This captivating B-type main-sequence star showcases a distinctive oblate shape, resulting in noticeable variations between its equatorial and polar diameters due to its rapid rotation. This unique characteristic grants Achernar star a remarkable visual appearance when viewed from Earth. As we delve into the mysteries of the cosmos, exploring the diameter of Achernar star offers a glimpse into the diversity and complexity of celestial objects that grace our night sky, sparking wonder and fascination.

Achernar Star Mass

The mass of Achernar star adds a captivating dimension to our understanding of celestial bodies. As a prominent B-type main-sequence star, Achernar boasts a mass of approximately seven times that of our Sun. This significant mass not only contributes to its luminosity but also plays a pivotal role in shaping the star's behavior and interactions within its cosmic surroundings. Exploring the mass of Achernar star illuminates the intricate dynamics at play in the universe, underscoring the diversity and complexity of stars that grace our night sky.

Achernar Star Luminosity

The luminosity of Achernar star, shines as a remarkable aspect that captivates astronomers and space enthusiasts alike. This B-type main-sequence star's luminosity stands out due to its considerable brightness, which is a result of its high energy output. Achernar's luminosity is a testament to its youth and mass, making it one of the brightest stars in the night sky. Exploring the luminosity of Achernar star offers a glimpse into the powerful forces at play in the cosmos, igniting our curiosity about the vibrant celestial objects that grace our universe.

Achernar Star Temperature and Spectral Color

With a surface temperature around 14,000 degrees Celsius (25,000 degrees Fahrenheit), Achernar star emits a radiant blue-white glow. This spectral color reflects the immense heat present on its surface and underscores its prominence in the cosmic tableau.

Achernar Star Distance From Earth

Achernar star graces the constellation Eridanus, situated at an approximate distance of 139 light-years from Earth. Its relative proximity offers a fascinating target for observation and study, allowing astronomers to gather valuable insights into its properties.

Achernar Star

Here's a detailed specification table for Achernar star, highlighting its key characteristics:

Characteristic Achernar Star (Alpha Eridani)
Star Type B-type Main-Sequence
Age (approx.) ~30 million years
Size (diameter) Oblate Shape, Variable
Mass (relative to Sun) ~7 times
Luminosity High
Surface Temperature ~14,000°C (25,000°F)
Spectral Color Blue-White
Distance from Earth ~139 light-years


Achernar in Mythology and Culture

Achernar has been known to humans since ancient times, and has been the subject of many myths and legends. In ancient Arabic astronomy, Achernar was known as "the mouth of the southern river," and was thought to mark the end of the Milky Way. In Australian Aboriginal astronomy, the star was known as "Altjira," and was associated with the creation of the world and the coming of the first humans.

In modern culture, Achernar has been featured in many science fiction stories and movies, often as a setting for alien planets or star systems. It has also been referenced in popular culture, including in the television show "Battlestar Galactica," where it was the location of a pivotal battle in the show's second season.

Achernar vs Sun

Achernar, often overlooked in casual sky gazing, is a star that offers a striking contrast to our familiar Sun. Situated approximately 139 light-years away in the constellation of Eridanus, Achernar is renowned as one of the flattest stars due to its rapid rotation. When we examine its properties alongside those of our Sun, the differences are startling. The Sun, a G-type main-sequence star, provides life-giving energy to our planet. In contrast, Achernar, a B-type main-sequence star, shines with a brilliance nearly 3,150 times that of the Sun and has an equatorial diameter almost seven times larger. But what truly sets Achernar apart is its unique oblate shape, resulting from a rotation speed that is staggering in comparison to the leisurely pace of our Sun. Diving deeper into the characteristics of these celestial bodies offers a wealth of knowledge about the diversity and splendor of the universe.

Comparison Table:

Below is a comparison table between Achernar and the Sun. Please note that Achernar is a prominent star in the constellation Eridanus, while the Sun is the star at the center of our solar system.

Aspect Achernar Sun
Type Hot, B-type main-sequence star G-type main-sequence star (Yellow Dwarf)
Spectral Class B3Vpe G2V
Mass Approximately 6.7 times the Sun's mass 1 Solar Mass
Radius Around 6 times larger than the Sun 1 Solar Radius
Luminosity Roughly 3,150 times brighter than the Sun 1 Solar Luminosity
Temperature About 15,000 Kelvin Around 5,500 Kelvin
Color Bluish-white Yellow
Age Relatively young (estimated around 30 million years) Around 4.6 billion years
Distance Approximately 139 light-years from Earth 1 Astronomical Unit (average distance to Earth)
Constellation Eridanus N/A (Center of the Solar System)
Rotation Speed Extremely rapid (projected equatorial speed of around 225 km/s) Different rotation rates across its equator and poles
Solar System Impact Not relevant Essential for the Solar System's stability and energy source
Energy Generation Nuclear fusion in its core Nuclear fusion in its core


Achernar is a fascinating star with many unique properties and characteristics. From its rapid rotation to its strong stellar wind and its location in the southern sky, Achernar has captured the attention of astronomers and stargazers for centuries. Its importance in various cultures and mythologies adds to its allure, and it continues to inspire and intrigue people to this day.

Despite being relatively close to Earth, Achernar is not easily visible from most parts of the world. However, for those fortunate enough to live in the southern hemisphere, it is a stunning sight to behold. With its distinctive blue-white color and brightness, it is a beautiful addition to the night sky.

Scientists continue to study Achernar to learn more about its unique properties and characteristics. Its rapid rotation and strong stellar wind make it an interesting subject for research, and its location in the southern sky means that it is well-positioned for observation by astronomers in the southern hemisphere.

In conclusion, Achernar is a star that is rich in history, culture, and scientific significance. Its unique properties and characteristics make it a fascinating subject for study, and its beauty and mystery continue to captivate and inspire stargazers and astronomers alike.

More Star Topics:

More Stars:

Back to blog