Eta Carinae is one of the most massive stars in our Galaxy. It underwent
a massive outburst in the 1840s, during which is became the brightest
star in the night sky. Now, however, it is shrouded by the dust ejected
during that outburst. Eta Carinae is believed to one of a twin
(or binary) star
system, with the two stars revolving around each other in 5.5 years.
The interaction between the two stars leads to a 5.5-year cycle in
the appearance of the system.
