Omega Centauri, Galaxy’s Largest Globular Cluster, Is Too Busy For Life

As astronomers keep on looking for signs of life beyond our planet, one place in the Milky Way seems to be completely inhospitable, reports Phys.org.

A new study by scientists from the University of California in Riverside (UCR) has examined the potential to host life of Omega Centauri, the largest globular cluster in the entire galaxy, and found that it has virtually none.

The research, due for publication in the Astrophysical Journal and currently available on the pre-print server arXiv, takes an in-depth look at direct observations of the cluster’s core, taken with the Hubble Space Telescope.

By calculating the span of the Habitable Zone around these core stars, the scientists uncovered that Omega Centauri doesn’t have the right stellar environment to support the development of life.

What Is Omega Centauri?

As the Inquisitr previously reported, globular clusters are ancient collections of stars bound in a spherical shape by the strong gravitational attraction between them.

Home to millions of stars, globular clusters go back almost to the galaxy’s early days and are very rare. For instance, the Milky Way only has less than 200 globular clusters, the largest of which is Omega Centauri.

Located 15,800 light-years away in the Centaurus constellation, this massive star cluster is 150 light-years wide. Made up of nearly 10 million stars, Omega Centauri can be seen in the sky with the unaided eye and has been frequently scoured by Hubble.

The globular cluster’s core is particularly crammed with stars, which piqued astronomers’ interest and made them wonder whether there could be potentially habitable planets orbiting these stars.

“Despite the large number of stars concentrated in Omega Centauri’s core, the prevalence of exoplanets remains somewhat unknown,” said study lead-author Stephen Kane, an associate professor of planetary astrophysics in UCR’s Department of Earth Sciences. “However, since this type of compact star cluster exists across the universe, it is an intriguing place to look for habitability.”

Crowded Neighborhood

As it turns out, this may not be the case. Kane’s team looked at 470,000 stars in the core of Omega Centauri’s core and found out that they’re too tightly-packed to have habitable planets.

Of the entire star sample, 350,000 were particularly interesting, since they stood a better chance of harboring life-bearing planets, judging by their color — a measure of stellar temperature and age.

The team calculated the extent of the Habitable Zone for each of these stars and discovered that it sits a mere 0.5 AU of the host star, which is half the distance between Earth and the sun. (1 AU, or astronomical unit, defines the average distance from us to the sun, established at about 150 million kilometers, or 93 million miles.)

At the same time, the core stars of Omega Centauri sit incredibly close to each other, snuggled at a distance of 0.16 light-years from one another. By comparison, the sun is 4.22 light-years away from its nearest neighbor, Alpha Centauri.

This means that the cluster’s core stars have “a relatively high rate of stellar close encounters that would disrupt planetary orbits within the Habitable Zone of typical Omega Centauri stars,” shows the new study.

“The rate at which stars gravitationally interact with each other would be too high to harbor stable habitable planets,” explains study co-author Sarah Deveny, a graduate student at San Francisco State University in California.

While it may look like a dead end (literally), Omega Centauri actually opens up the horizon in the search for signs of alien life. If anything, it has shown that astronomers must turn to “globular clusters with lower encounter rates” among their stars, which “might lead to a higher probability of finding stable habitable planets,” notes Deveny.