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Eta Carinae

Posted: December 30th, 2012, 1:00 am
by Christopher K.
Today's APOD is a 1996 image of Eta Carinae, located in the diffuse Keyhole Nebula. This famous object is almost certainly going to go supernova, and we may not have to wait long for the event. At this time some have taken to calling it a hypergiant as the term "supergiant" falls short of conveying its luminosity.

Halley recorded the star as fourth magnitude in 1677. Over the following hundred years, Eta Carinae's variations in magnitude were almost comical...
1730, reaches second magnitude
~1782, falls to fourth magnitude
~1801, brightens
~1811, goes back to fourth magnitude
1820, begins to brighten consistently
1822, reaches second magnitude
1827, reaches first magnitude

After 1827, it took about five years to go back down to second magnitude, then rebrightened to a level comparable with Rigel. After a slight dimming, it rose to the brightest its been in modern astronomical study, -0.8. That's right--it was the second-brightest star in the night sky! Thereafter occurred a slow fading, leading to the star going below the unaided-eye threshhold in 1868.

Its changes in magnitude after that date are relatively sedate. During the first three decades of the twentieth century it was of eighth magnitude. During World War II it started to rebrighten, reaching about seventh magnitude in the mid-1950s. It's even brighter these days. If this "magnitude shuffle" isn't impressive enough, one of the strongest lines in Eta Carinae's spectrum is the hydrogen-alpha line, and at some infrared wavelengths it and the lobes of material ejected from it are the brightest non-Solar System objects.

Investigation into whether it has a companion is underway. Eta Carinae teases Baton Rouge, rising to zero degrees altitude to skirt our horizon--and retreat.


More information:
Burnham's Celestial Handbook, pp.466-471. ... rinae.html

Re: Eta Carinae

Posted: July 20th, 2020, 11:29 pm
by Christopher K.
Interested in all Eta Carinae, all the time? The University of Minnesota has you covered with a voluminous site for the star--and its companion, discovered (I believe) in the late 1990s.

The site: