Friday, January 6, 2023

Eta Carinae, the star at the point of exploding.

Eta Carinae is an unstable blue hypergiant star situated 7500 light-years from Earth, visible in the constellation of Carena.

The star is one of the most massive and luminous of the entire galaxy: its mass is in fact one hundred times that of the Sun, while its brightness is more than five million times that of the Sun!

When we look at Eta Carinae we are not able to see the star directly, but only the nebula that surrounds it, known as the Homunculus Nebula. This nebula is formed by gases that the star continues to expel: being in the final stages of its life and being so massive Eta Carinae in fact expels into space much of its mass.

The inner, spherical, greyish-pink part of the nebula was formed by a stellar explosion observed from Earth 170 years ago. The explosion ejected into space an unbelievable amount of material, 10 solar masses, and made Eta Carinae for a short time the second brightest star in the sky after Sirius!

Although almost two centuries have passed the nebula gas is still expanding at an impressive speed: think that at its current speed the gas would cover the distance that separates the Earth from the Moon in just 20 seconds!

All this is a sign of an impending end: the star is indeed destined to explode in hypernova in a few thousands of years.

Credit: NASA, ESA, Hubble.

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