The work of Dr. John Martin, professor of astronomy-physics at UIS, was the focus of a press event at the American Astronomical Society (AAS) winter meeting in Washington D.C. on January 4. Martin, along with an international team of researchers, obtained new data about the Eta Carinae star system using a Near-Infrared Coronagraphic Imager (NICI) at the Gemini Observatory's Gemini South telescope in Chile.
In April 1843, the Eta Carinae system underwent a huge 20-year outburst that, throughout some of that period, made it the sky’s second brightest stellar object. During the “Great Eruption,” astronomers estimate that about 20 times the mass of the Sun was ejected into interstellar space. Today, astronomers study this relatively nearby stellar oddity to help understand the late evolution of massive stars – a messy process involving outflows, eruptions, strong magnetic fields and powerful jets.
The result of this activity is reflected in a new image captured by Martin and his team of researchers. Gemini Observatory released the image showing previously hidden forensic secrets at the ballistic core of the Homunculus Nebula, part of the Eta Carinae system. Adaptive optics were used to remove atmospheric blurring in the image.
Martin’s team used NICI to study gas and dust features surrounding the central star where the complex structure includes an intricate network of wispy clouds, inspiring the “Butterfly Nebula” moniker. The data also uncover a feature never directly imaged before called the Little Homunculus Nebula.
"The Homunculus is an evolving corpse of a dying star, and most of what we see is the visible outer layer, like a skin, from the Great Eruption. The Little Homunuclus is under that skin," Martin said. "The Gemini images have allowed us to perform something akin to an autopsy by peeling away the obscuring, outer dusty skin and giving us a glimpse of what’s inside. In the process, we're finding things we have never imaged before and didn't expect."
Eta Carinae, located only about 7,500-8,000 light years away, consists of at least two stars at its core, the largest of which is among the most luminous and massive stars in our galaxy having a mass of at least 100 times that of the Sun. The system is visible to the naked eye from the southern hemisphere and very low northern latitudes.
Martin and his team hope that their new observations will soon trace the uncertain history of a minor eruption in the Eta Carinae system in the late 1890s.
The research team also includes Etienne Artigau (University of Montréal, Canada, lead author on subsequent paper and previously at Gemini South), Kris Davidson (University of Minnesota), Roberta Humphreys (University of Minnesota), Olivier Chesneau (FIZEAU, France), and Nathan Smith (University of California).