RT @fedhere: We discovered #lightechoes of #etacarinae !

During the middle of the 19th century, a star system known as Eta Carinae
suddenly became the second-brightest star in the night sky, then
gradually faded again. Known as the Great Eruption, this event
released about 10 percent of the energy that would have been liberated if the star had gone
supernova, and caused the star to shed approximately 10 Suns' worth of mass. Yet somehow, Eta Carinae
survives to this day. Understanding the behavior of Eta Carinae (which is
estimated to still hold at least 100 times the mass of our Sun) will provide
astronomers with knowledge of the end-stages of very
massive stars, and allow them to distinguish between
eruptions and supernova explosions.

Even though the Great Eruption first became visible in 1838,
astronomers are still able to observe its effects today
through light echoes: light that has bounced off particles inside the
nebula surrounding Eta Carinae for a while, and has reached Earth long after the
initial eruption has faded. A new study of the light echoes, performed by
A. Rest et al., reveals that
Eta Carinae was relatively cool at the time of its brightening. While eruptions observed in other galaxies seem to be driven by thick, opaque clouds
of matter being driven away from their progenitor star, the analysis published in
the February 16 edition of Nature seems to show that the
Great Eruption may actually have been triggered by a blast
wave emanating from the surface of Eta Carinae.







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