Eta Car was once a very bright star (one of the brightest in the sky, naked eye speaking) back sometime in the 1800s (1840s it reached magnitude -1). It then faded from naked eye view until in the last 50+ years it has been gradually brightening.
See
http://ar.geocities.com/varsao/Curva_Eta_Carinae.htm for discussions on its more recent variations (seems there might be a yearly pattern?)
Seems it might an eclipsing binary (X-ray) with predicted brightening:
http://www.aavso.org/news/etacar.shtml
(X-ray info:
http://asd.gsfc.nasa.gov/Michael.Cor...rve/index.html)
Wikipedia has some good info too:
http://en.wikipedia.org/wiki/Eta_Carinae