NASA’s Chandra Rewinds the Story of the Big Bang of the 1840s

Using snapshots taken over 20 years with NASA’s Chandra X-ray Observatory, astronomers have learned important new details about an eruption from Eta Carinae seen on Earth in the mid-19th century.

Decades of Chandra data have been combined into a new movie containing Eta Carinae frames from 1999, 2003, 2009, 2014 and 2020. Astronomers used Chandra observations with data from ESA’s (European Space Agency’s) XMM-Newton. Watch a starburst from 180 years ago expand through space at 4.5 million miles per hour. New insights from Eta Carinae show how different space observatories can work together to help understand changes in the universe unfolding on human timescales.

A paper describing these results appears in The Astrophysical Journal.

Eta Carinae is a system of two massive stars (one believed to be 90 times the mass of the Sun and the other 30 times the mass of the Sun). In the mid-19th century, Eta Carinae was observed to experience a massive explosion, which astronomers called the „Big Bang”. During this event, Eta Carinae was ejected 10 to 45 times more than the Sun. This material became a dense pair of spherical clouds of gas on opposite sides of the two stars, now known as the Homungulus Nebula.

The bright ring of X-rays around the Homunculus Nebula was discovered about 50 years ago and studied in previous lunar work. Chandra’s new movie, an in-depth picture created by piecing together data, reveals important clues about Eta Carinea’s volatile history, including the ring’s rapid expansion and a previously unknown X-ray-dense shell outside it.

„We have interpreted this faint X-ray shell to be the blast wave of the Big Bang in the 1840s,” said Michael Corcoran of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who led the study. „It tells an important part of Etta Carinae’s story that we wouldn’t have known otherwise.”

Because the newly discovered outer X-ray shell has a similar shape and orientation to the Homungulus Nebula, Corcoran and his colleagues hypothesize that the two structures have a common origin.

Material erupted from Eta Carinae before the 1843 Big Bang — sometime between 1200 and 1800, based on the movement of gas clusters previously seen in data from NASA’s Hubble Space Telescope. Then, a fast blast wave from the big bang tore through space, crashing and heating the clump to millions of degrees, creating a bright X-ray ring. The blast wave has now traveled beyond the bright ring.

„The shape of this faint X-ray shell is a plot twist in my mind,” said co-author Kenji Hamaguchi, a researcher at the University of Maryland, Baltimore County and NASA Goddard. „This shows us that the dim shell, the homunculus, and the bright inner ring all likely came from an explosion from the star system.”

With XMM-Newton, the researchers observed that Eta Carinae’s X-ray brightness has faded over time, along with previous observations of the system obtained by NASA’s Neutron Star Interior Composition Explorer (NICER) telescope aboard the International Space Station. The authors used a simple model to estimate how bright Eta Carinae was in X-rays during the big bang, and combined this with the velocity of the object determined from the movie to estimate how quickly the supermassive gas was ejected. .

The researchers combined this information with an estimate of how much gas was ejected to determine whether the big eruption consisted of two eruptions. The first, rapid ejection of a small volume of fast, low-density gas produced an X-ray burst wave. This was followed by a slow ejection of dense gas eventually forming the Homunculus Nebula.

A team led by Nathan Smith of the University of Arizona, one of the co-authors of the new X-ray study, had previously suggested that the Big Bang was caused by the merger of two stars that had originally existed three times. It also explains the ring-like structure seen in X-rays, as it ejects material in a flat plane.

„Etta Carine’s story just keeps getting more interesting,” Smith said. „All evidence suggests that Etta Karine survived a very powerful explosion that would normally destroy a star. I can’t wait for the next episode to see what other surprises Etta Karine has in store for us.”