“Globular cluster may be the first place to associate intelligent life in our galaxy,” says Rosanne Di Stefano of the Harvard-Smithsonian center for astrophysics. Globular clusters of stars differ from other. They are tightly Packed, hold a million stars in a ball just 100 light-years. They are old, the age of the milky Way. And according to scientists, they may also perfectly be suitable for learning search space civilizations.
In our galaxy the milky Way has about 150 globular clusters, most of which revolve on the outskirts of the galaxy. They were formed about 10 billion years ago, on average. Their stars contain less heavy elements required to create planets, since these elements (like iron and silicon) had to be created by older generations of stars. Some scholars argue that because of this, globular clusters are unlikely to be planets. In fact, so far, only one planet was found in a globular cluster.
And yet Di Stefano and her colleague Alak ray (Institute Tata of fundamental research, Mumbai) argue that we should not underestimate the power of globular clusters. Extrasolar planets were found around stars that contained ten times less metal than our Sun. And while a planet the size of Jupiter is found predominantly around stars containing high levels of heavy elements, scientists have found that smaller planets the size of Earth do not have such preferences. “Too early to say that globular clusters there are no planets,” says ray.
Another problem is that the crowded environment of the globular cluster may represent a threat to any planets formed. Nearby star may get too close and gravity to disrupt the planetary system, throwing the world into interstellar space ice. However, the potentially habitable zone of a star is the distance at which the planet is warm enough for liquid water existence, depends directly from the star. The brighter stars habitable zone farther, the same planet orbiting a dim star should be much closer. Stars brighter and live on less, and because globular clusters are old, these stars have already died out. Most globular clusters dim and long-lived red dwarfs. Any possible habitable planets around them are relatively safe from stellar interactions.
“After the planets formed, they can persist over long periods of time, even more than the age of the Universe,” explains Di Stefano, who presented their research at the meeting of the American astronomical society.
So if habitable planets can form in globular clusters and survive for billions of years, what will be the consequences for life in this case? Life will have enough time to become complex and may even develop intelligence.
Such a civilization will be in a completely different environment. The nearest star to our Solar system is four light years or 30 trillion kilometers. Within globular clusters the nearest star is 20 times closer — just one and a half trillion kilometers. Interstellar communication and exploration will be easier.
“We call it “opportunity globular clusters,” says Di Stefano. — Data transfer between the stars will take no longer than a letter from the US to Europe in the 18th century. Interstellar travel will also be more affordable. The probes Voyager 100 billion miles from Earth, or one tenth the distance from the nearest star, if we were in a globular cluster. Thus, to send an interstellar probe for a civilization of our technological level in the globular cluster wouldn’t work”.
The nearest globular cluster is a few thousand light-years from Earth, which significantly complicates the search for planets, especially in the crowded core of the cluster. However, it is possible to search the planets wandering in the outskirts of globular clusters. Perhaps astronomers could detect free-floating planets using gravitational lensing.
Even more intriguing idea may be the direction of the globular cluster search and methods of SETI, trying to find a radio or laser transmission.