Astronomers have discovered crucial new information on an eruption from Eta
Carinae that was observed on Earth in the middle of the 19th century, thanks
to images captured over a 20-year period with NASA's Chandra X-ray
Observatory.
Ten years' worth of Chandra data have been merged into a new video with
frames from 1999, 2003, 2009, 2014, and 2020 of Eta Carinae. Using
information from ESA's (European Space Agency) XMM-Newton and Chandra
images, astronomers are able to track the star eruption that occurred 180
years ago as it continues to explode into space at velocities of up to 4.5
million miles per hour. Eta Carinae has provided fresh insights into how
various space observatories might collaborate to support our understanding
of changes in the cosmos that occur on human timescales.
These findings are published in The Astrophysical Journal in a
publication.
Two enormous stars, one around 90 times the mass of the sun and the other
estimated to be about 30 times the mass of the sun, are part of the Eta
Carinae system. Astronomers have named the massive explosion that occurred
in the middle of the 19th century on Eta Carinae the "Great Eruption." Eta
Carinae expelled material that was between 10 and 45 times the mass of the
sun during this event. On opposite sides of the two stars, this material
developed into a dense pair of spherical clouds of gas known as the
Homunculus Nebula.
About half a century ago, a brilliant X-ray ring surrounding the Homunculus
Nebula was identified and examined in earlier Chandra research. Important
clues about the turbulent past of Eta Carinae are revealed by the Chandra's
latest movie and a deep image created by combining the data, including the
ring's quick growth and a faint shell of X-rays that was previously
unidentified.
Leading the study was Michael Corcoran of NASA's Goddard Space Flight
Center in Greenbelt, Maryland. "We've interpreted this faint X-ray shell as
the blast wave from the Great Eruption in the 1840s," Corcoran said. "It
reveals a significant portion of Eta Carinae's past that we would not have
known otherwise."
Corcoran and colleagues believe that the Homunculus Nebula and the recently
found outer X-ray shell have a common ancestor because to their comparable
shapes and orientations.
It is hypothesized that material was expelled from Eta Carinae far in
advance of the 1843 Great Eruption, i.e., between 1200 and 1800, based on
the mobility of gas clumps previously observed in Hubble Space Telescope
data. The brilliant X-ray ring was later formed as the rapid blast wave from
the Great Eruption tore through space, meeting with the clumps and scorching
them to millions of degrees. Now the blast wave is past the luminous
ring.
According to co-author Kenji Hamaguchi, a researcher at NASA Goddard and
the University of Maryland, Baltimore County, "the shape of this faint X-ray
shell is a plot twist." "It indicates that the bright inner ring, the
Homunculus, and the faint shell are probably all products of star system
eruptions."
Using XMM-Newton, the scientists observed that Eta Carinae's X-ray
brightness has decreased over time, which is consistent with earlier system
studies made using NASA's Neutron Star Interior Composition Explorer (NICER)
instrument on the International Space Station. The brightness of Eta Carinae
in X-rays during the time of the Great Eruption was estimated by the authors
using a straightforward model. They then coupled this estimate with the
material's speed, which they calculated based on the video, to calculate the
rate at which the high-speed gas was expelled.
Based on this data and an approximation of the gas released, the
researchers concluded that the Great Eruption was most likely the result of
two explosions. The X-ray blast wave was originally created by a brief
expulsion of a little quantity of rapid, low-density gas. The slower outflow
of dense gas that ultimately resulted in the formation of the Homunculus
Nebula came next.
One of the co-authors of the new X-ray research, Nathan Smith of the
University of Arizona, leads a team that has previously proposed that the
Great Eruption was produced by the merging of two stars in what was formerly
a triple system. Since it would result in material being ejected in a flat
plane, this would also explain the ring-like shape visible in X-rays.
Smith remarked, "The Eta Carinae story just keeps getting more
interesting." "Every piece of evidence points to Eta Carinae surviving a
massive explosion that would typically destroy a star. I'm eager to see what
further surprises Eta Carinae has in store for us in the upcoming data
installment."
Provided by NASA
