Superstar Eta Carinae May Have Cousins in Other Galaxies

Eta Carinae is best known for an enormous eruptions seen in the mid-19^th century that hurled an amount of material at least 10 times the sun's mass into space, giving it a shroud that made it the only object of its kind known in our galaxy. Now, scientists have found five similar objects in other galaxies for the first time.

"The most massive stars are always rare, but they have tremendous impact on the chemical and physical evolution of their host galaxy," said Rubab Khan, one of the researchers, in a news release.

Eta Carinae is located about 7,500 light-years away in the southern constellation of Carina. It outshines the sun by about 5 million times and consists of two massive stars in a tight, 5.5-year orbit. Astronomers estimate that the more massive star has about 90 times the sun's mass, while the smaller companion may exceed 30 solar masses.

As one of the nearest laboratories for studying high-mass stars, Eta Carinae has been a unique, important astronomical touchstone since its eruption in the 1840s. In order to understand why the eruption occurred and how it relates to the evolution of massive stars, astronomers needed additional examples. Catching rare stars during the short-lived aftermath of a major outburst is highly difficult, and nothing matching Eta Carinae had been found until now.

The researchers conducted a survey in 2015 that revealed two candidate Eta twins in the galaxy M83, located 15 million light-years away, and one each in NGC 6946, M101, and M51, located between 18 million and 26 million light-years away. These five objects mimic the optical and infrared properties of Eta Carinae, which indicates that each may contain a high-mass star buried in five to 10 solar masses of gas and dust.

The findings give researchers a few more of these stars to study, which may help them better understand how they form.

The findings are published in The Astrophysical Journal.

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