Globular star clusters have the potential to host interstellar civilizationsAmy Walsh (Author) Published Date : Jan 07, 2016 14:02 ET
Globular star clusters are excellent places to find space-faring civilizations. Harvard-Smithsonian Center for Astrophysics (CfA) has presented a new research at a meeting of the American Astronomical Society stating how extraordinary these clusters are.
They are densely packed and extraordinary. They hold a million stars in a ball only about 100 light-years across on average. They are as old as the Milky Way.
Lead author Rosanne DiStefano stated that the first place where intelligent life is identified in our galaxy is a globular cluster.
About 150 globular clusters are hosted by our Milky Way and a majority of them are orbiting in the galactic outskirts. On average, they were formed about 10 billion years ago. As a result, their stars contain fewer of the heavy elements needed to construct planets, since those elements (like iron and silicon) must be created in earlier generations of stars.
There have been arguments from certain scientists that this makes globular cluster stars less likely to host planets. In fact, only one planet has been found in a globular cluster till date.
Stating that this is too pessimistic, DiStefano and her colleague Alak Ray (Tata Institute of Fundamental Research, Mumbai) argue that exoplanets have been found around stars only one-tenth as metal-rich as our Sun. While Jupiter-sized planets are found preferentially around stars containing higher levels of heavy elements, no such preference is cited by smaller, Earth-sized planets.
Planets that get formed face a threat from a globular cluster's crowded environment. A planetary system might get disrupted with a neighboring star that could wander too close. This could throw these worlds into icy interstellar space.
However, a star's habitable zone depends on the star. The habitable zone means the distance at which a planet would be warm enough for liquid water.
The predominant stars in globular clusters are faint, long-lived red dwarfs. Any potentially habitable planets hosted by predominant stars in globular clusters would orbit nearby and be relatively safe from stellar interactions.
Once planets form, they can survive for long periods of time, even longer than the current age of the universe, explains DiStefano.
The nearest star within a globular cluster is just about 20 times closer, which means that the interstellar communication and exploration will get significantly easier as compared to our nearest star.
DiStefano says, Interstellar travel will consume lesser time. That means sending an interstellar probe is something a civilization at our technological level could do in a globular cluster.
Globular star clusters have the potential to host interstellar civilizations