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Home / Science / No place at home in the crowded core of Omega Centauri – Astronomy Now

No place at home in the crowded core of Omega Centauri – Astronomy Now



The star-wrapped core of Omega Centauri, one of the largest globular clusters in the Milky Way, and a popular target for amateur astronomers. This breathtaking view was taken by the Hubble Space Telescope. Image: NASA, ESA and the Hubble SM4 ERO Team

Omega Centauri, the Milky Way's largest globular cluster and a popular destination for amateur astronomers in the southern latitudes, is littered with around 1

0 million stars. One can only imagine the glow of the night sky an alien could enjoy from a planet orbiting a star in the center of the cluster. But based on a new study, aliens – and stable solar systems – are unlikely to be found.

Writing in The Astrophysical Journal, Stephen Kane, a planetary astrophysicist at the University of California-Riverside, and Sarah Deveny, a graduate student at San Francisco State University, concluded that stars at the core of Omega Centauri are so close together that disturbing gravitational interactions would occur about every one million years.

That would almost certainly prevent the formation of solar systems with planets in stable orbits, the time scales necessary to evolve.

By comparison, the nearest star to the Sun of Earth is located in the Alpha Centauri system about 4.2 light years – 40 trillion kilometers (25 billion miles) away. At the core of Omega Centauri, the average distance between the stars is only 0.16 light-years or 1.5 trillion kilometers (970 billion miles).

Omega Centauri, as shown by the VLT Survey Telescope of the European Southern Observatory. Image: ESO / INAF-VST / OmegaCAM. Acknowledgments: A. Grado, L. Limatola / INAF Capodimonte Observatory

"The speed with which stars interact gravitationally would be too high to accommodate stable, habitable planets," said Deveny. "Looking at clusters with similar or higher encounter rates to Omega Centauri might lead to the same conclusion, so studying lower-pooled globular clusters could make it more likely to find stable, habitable planets."

The conclusions were based based on an analysis of 350,000 stars at the core of Omega Centauri at the right temperature and age based on their color to accommodate exotropic life. Because most of the stars are red dwarfs at heart, their habitable zones where liquid water could exist would be much closer to their home tribes than the habitable region orbiting the earth.

"The core of Omega Centauri could potentially be populated with a plethora of compact planetary systems that host habitable zone planets close to a host star," Kane said. "An example of such a system is TRAPPIST-1, a miniature version of our own solar system that is 40 light-years away and currently considered one of the most promising places to look for extraterrestrial life."

But the numbers do not seem to work for stars in the cores of large globular clusters. When astronomers and amateurs train their telescopes on Omega Centauri, it's unlikely anyone will look back.


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