Astrophysicists affiliated with UCSB and the Las Cumbres Observatory Global Telescope Network have recently begun researching 170-year-old Eta Carinae, a behemoth double-star system that erupted over a century ago.
Frederica Bianco, a postdoctoral researcher at UCSB, and Andy Howell, a staff scientist at LCOGT, used the LCOGT’s Faulkes Telescope South in Siding, Australia to record the aftermath of the explosion and compare their observations to those of aboriginal Australians who witnessed the same event in the 1830’s.
The Eta Carinae is a stellar system comprised of two stars about 8,000 light-years away from the Sun. In the late 1830s, the system began a 20-year explosion and ejected hot gas with a mass nearly 20 times that of the Sun. At its peak, Eta Carinae was the second-brightest astronomical body in the night sky. After the explosion, the system’s luminosity faded until recent decades.
According to Howell, very massive stars, such as those in the Luminous Blue Variable category, have a tendency to erupt periodically. Still, the cause of Eta Carniae’s eruption remains a mystery.
Eta Carinae’s explosion was not caused by stellar winds, as was initially hypothesized, and is characteristic behavior of “normal” supernovae imposters.
According to Bianco, Eta Carinae’s eruption was visible to the naked eye, even during daylight hours.
“The ‘Great Eruption’ was so bright and its variations so extreme that we have records of it not only by astronomers and scientists at that the time, but even in the oral tradition of the Aboriginal cultures,” Bianco said. “Being able to re-observe an eruption witnessed in the 1800s can give us great insight in how massive stars work.”
Modern studies and improved technology have allowed astronomers to observe the eruption firsthand. Furthermore, the ability to witness Eta Carinae’s eruption with improved technology presents a unique opportunity to understand stellar explosions and how stars work in general.
“Stars like this are excellent laboratories for extreme physics that we can’t probe in laboratories on Earth,” Howell said.
Scientists were able to observe and identify Eta Carinae’s light echo 170 years after the explosion, as light from the original eruption is now being reflected off lingering dust.
“Technically what we do is subtract an old image from a more recent one,” Bianco said. “We look for regions that have brightened between the epochs of the two images.”
Howell added that the nebula — clouds of interstellar dust or gas — of material ejected in the mid-1800s eruption is observable in great detail and, for this reason, scientists are hopeful that their observations of this eruption could reveal important information about large star behavior.
“Eta Car provides tremendous insight in the life of massive stars. We can add the missing pieces to the puzzle,” Howell said.