Goodbye to a beauty of the night sky
The star Eta Carinae is one of the most luminous and enigmatic of the Milky Way. Part of its nature has been revealed through the Homunculus nebula ejected in 1847, in a Giant Eruption when the star could be seen in broad daylight. This exuberant nebula distinguishes Eta Carinae from other similar stars – the Blue Luminous Stars (LBVs) – because their nebulae are not so clearly visible. Aside from making it one of the most beautiful and frequently photographed objects in the night sky, this giant nebula contains information about its parent star in the energy of its expansion, bipolar outflow and chemical composition.
However, we will not be able to see the nebula clearly for much longer as a recent study indicate that the Homunculus nebula will be obsfucated by the brightness of the central star in the incoming years. The star¢s brightness is increasing so rapidly that in the year 2036 the star will 10 times brighter than its nebula, when it will finally look like the other LBVs.
This work proposes that Eta Carinae¢s increase in brightness, is not intrinsic to the star as many researchers imagined, but rather it is caused by the dissipation of a dust cloud positioned exactly in front of it, to our direction. This cloud completely shrouds the star and its winds, blotting out most of its light traveling towards us while the Homunculus Nebula can be seen directly, as it is 200 times bigger than the obscuring cloudet and its brightness is almost unaffected. In 2032±4 years the dusty cloud will have disappeared, the brightness of the star will not increase anymore and the Homunculus will be lost in its glare.
Augusto Damineli from University of Sao Paulo says: "In a few years, we will lose the opportunity to take beautiful photos of the Homunculus, but we will see more clearly the pair of twin stars inside. The multiple quasi-periods we revealed will be monitored more accurately than before."
The article is being published in the Monthly Notices of the Royal Astronomical Society by a group of 17 authors, led by Augusto Damineli of the IAG-USP (Br) and can be accessed at the link:(http://arxiv.org/abs/1901.00531).
Animation plus Interview with A. Damineli (in Portuguese):
Figure 1. left: Eta Carinae image by HST / NASA in the year 2000 (Credit: N. Smith and J. A. Morse); Right: prediction for 2036, when the star will obfuscate its nebula.
Contact: Augusto Damineli: email@example.com
Department of Astronomy of IAG-USP