New York: Contradicting current beliefs, a team of researchers, including one from India, has said that globular star clusters that hold a million stars in a ball only about 100 light-years across on average could also host planets with intelligent life.
Globular star clusters are extraordinary in almost every way. Dating back almost to the birth of the Milky Way, they are densely packed with stars. And according to this new research, they also could be extraordinarily good places to look for space-faring civilizations.
"A globular cluster might be the first place in which intelligent life is identified in our galaxy," said lead author Rosanne DiStefano of the Harvard-Smithsonian Center for Astrophysics (CFA) in the US.
Our Milky Way galaxy hosts about 150 globular clusters, most of them orbiting in the galactic outskirts. They formed about 10 billion years ago on average.
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.
Some scientists have argued that this makes globular cluster stars less likely to host planets. In fact, only one planet has been found in a globular cluster to date.
However, DiStefano and her colleague Alak Ray from Tata Institute of Fundamental Research, Mumbai, argue that this view is too pessimistic.
"It is premature to say there are no planets in globular clusters," Ray said.
So if habitable planets can form in globular clusters and survive for billions of years, what are the consequences for life should it evolve?
Life would have ample time to become increasingly complex, and even potentially develop intelligence, the researchers said.
Such a civilization would enjoy a very different environment than our own, according to the research.
The nearest star to our solar system is four light-years, or 24 trillion miles, away. In contrast, the nearest star within a globular cluster could be about 20 times closer - just one trillion miles away. This would make interstellar communication and exploration significantly easier.
"We call it the 'globular cluster opportunity'," says DiStefano.
"Sending a broadcast between the stars wouldn't take any longer than a letter from the US to Europe in the 18th century," DiStefano noted.
The research was presented at a meeting of the American Astronomical Society.