Achernar

3000 L ☉

Achernar, also known as α Eridani ( Alpha Eridani ), is the brightest star in the constellation Eridanus the river and one of the ten brightest stars in the sky. He is so far south that it is not visible from Europe.

It was observed in 2003 by the Very Large Telescope Interferometer (VLTI ), which revealed that he s is much flattened by its rapid rotation speed of at least 230 km /. The exact value of the rotational speed depends on the unknown orientation of the axis of rotation. It has an equatorial diameter is at least one and a half times the diameter at the poles.

History

The name of the star, Arabic آخر النهر / Ahiru ʾ n- Nahr, is derived from the old Arabic, meaning " the end of the river " because it marks the southern end of the river Eridanus. It replaced the - equally important - Acamar ( θ ( 1) Eridani ), which marks the end of the river in Ptolemaic Greek tradition. Achernar was in antiquity, circa 1500 BC, due to the precession of -76 ° declination, and even in Egypt could not be observed during Acamar just so handed over the horizon on Crete.

The late antique and early medieval small Asian sailors may have used it on their African journeys as a marker. There are also Bedouin -Arab representations of Achernar and Fomalhaut as a couple ostriches. Achernar also migrates into the next millennia further north. In 500 years, is Achernar ( α Eridani ) reach the horizon of Crete, and are visible from about 7900 AD to 10,500 AD, even in Germany. Then Achernar migrates back south. The next at the South Pole Achernar was 3360 BC, then at -83 ° declination.