Astronomers find ‘twins’ of massive star Eta Carinae

Best known for a massive, unexplained eruption in the 1840s that sent debris ten times the mass of the sun hurtling through space, Eta Carinae is said to be the brightest and heaviest star system within 10,000 light years of our galaxy—and the only object with an expanding dust veil.

However, a new an analysis of data from the Spitzer and Hubble space telescopes has revealed that Eta Carinae might not be quite so unique after all. In fact, scientists at the US space agency have now identified five new objects with properties similar to the star in other galaxies.

“The most massive stars are always rare, but they have tremendous impact on the chemical and physical evolution of their host galaxy,” lead scientist Rubab Khan, a postdoctoral researcher at the NASA Goddard Space Flight Center in Maryland, said in a statement Wednesday.

“We knew others were out there. It was really a matter of figuring out what to look for and of being persistent,” added co-investigator Krzysztof Stanek, an astronomy professor at Ohio State University in Columbus. Together, Khan, Stanek and colleagues from OSU and Goddard used a new technique to identify possible Eta Carinae twins—“Eta twins” for short.

Future research needed to fully flesh out their properties

Eta Carinae is located approximately 7,500 light-years from Earth and is five million times more luminous than our sun, according to NASA. It is a binary system featuring two stars in a 5.5-year orbit. One star is said to be 30 times larger than the sun, and the other is 90 solar masses.

In addition to being studied because it’s one of the closest high-mass stars, Eta Carinae has been a extensively analyzed by researchers trying to learn why it erupted during the 19th century, and how that behavior is related to the evolution of massive stars. In order to better understand what happened, however, additional examples need to be researched.

It is no easy feat spotting stars following such a massive outburst, and previous efforts to locate an Eta Carinae twin had proven unsuccessful. However, Khan’s team were able to develop a new type of infrared and optical fingerprint which they used to find the five candidate Eta twins.

The nearby spiral galaxy M83 is currently the only one known to host two potential Eta Carinae twins.  Credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA) and R. Khan (GSFC and ORAU)

The nearby spiral galaxy M83 is currently the only one known to host two potential Eta Carinae twins. Credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA) and R. Khan (GSFC and ORAU)

Two of the candidates were located in the galaxy M83, located 15 million light-years away. The third was found in NGC 6946, while the other two were detected in M101 and M51—all of which are located between 18 and 26 million light-years away, according to NASA.

Each of the stars had optical and infrared properties said to be similar to Eta Carinae, indicating that each is likely a high mass star surrounded by a gas and dust cloud between five and 10 solar masses in size, the study authors reported in the Astrophysical Journal Letters last month. Future studies are expected to reveal more precise information about their physical characteristics.


Feature Image: The eruption of Eta Carinae in the 1840s caused the Homunculus Nebula. Credit: NASA, ESA, and the Hubble SM4 ERO Team