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Super rare ‘monster’ star discovered

U. LEEDS (UK) — Astrophysicists have identified one of our galaxy’s largest and rarest stars, a yellow hypergiant, caught in its final throes.

Despite being cataloged in 1983, this is the first time the star, known as IRAS 17163-3907, has been identified as a yellow hypergiant. Out of a hundred billion stars in the Milky Way, this is only the third such monster star to be discovered.

The star is half a million times brighter than our Sun, but much of this light is given out in the infrared part of the spectrum, making it relatively dim to traditional telescopes. That’s why it took over 25 years for someone to study it in great detail, suggests René Oudmaijer, a professor of physics and astronomy at the University of Leeds who was part of the team that made the discovery.

“The star has a volume one billion times that of the Sun. If it was placed in the center of our solar system, Jupiter would orbit just above the star’s surface. Its size means that sometime in the future it will go supernova,” says Oudmaijer.

The dust and gas belched out by these stars can be seen in the two shells that surround the star. The first was puffed out almost a thousand years ago, but the inner shell was ejected within the last 300 years. The radius of these shells will tell astrophysicists about what massive stars do as they approach a supernova.

The appearance of the two spherical shells, led the researchers to dub the star the “Fried Egg Nebula.”

Oudmaijer says the star could help us to learn much more about stellar evolution.

“Every now and then, we have a big leap forward in our understanding. This could be one of those moments,” he adds. “It’s a very rare object from a stellar evolution perspective, and the double shell is a particularly important discovery. It tells us for the first time that material is ejected during several periods and not steadily in this late phase of a star’s life.”

Oudmaijer says the next gasp “might be this giant star’s last one.”

Oudmaijer adds: “As well as insights into stellar evolution, physicists hope to learn more about how massive stars influence galaxies. For example, the strong winds from these types of star are so powerful that they influence the shape of galaxies.”

The research was carried out by academics from European Southern Observatory (ESO), the Universities of Leeds and Manchester, and other institutions in Europe. Their findings are scheduled for publication in the journal Astronomy and Astrophysics.

More news from the University of Leeds: www.leeds.ac.uk/news

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