Sorry Jodie Foster, it’s not Vega. A pair of researchers is offering up a new place to look for alien life. Globular star clusters.
“A globular cluster might be the first place in which intelligent life is identified in our galaxy,” says lead author Rosanne DiStefano of the Harvard-Smithsonian Center for Astrophysics (CfA).
DiStefano presented the new research this week in a press conference at a meeting of the American Astronomical Society.
Why globular star clusters?
First, let’s talk about what globular star clusters are. Imagine a ball of space about 100 light years across, give or take. Now cram a million stars into this ball. That’s a globular star cluster.
Our galaxy (the Milky Way) has around 150 globular clusters. And most of these are found in the outer edges of the Milky Way. On average, each one formed about 10 billion years ago. Because of this, some scientists aren’t sold on the idea of planets in globular clusters. Why? The stars in these massive clusters don’t have as many heavy elements needed to create planets. Elements, like iron and silicon, must be created in earlier generation of stars they argue. And so far, the discoveries back them up. Astronomers have found just one exoplanet in a globular star cluster.
DiStefano and her colleague Alak Ray believe this is a ‘glass half-empty approach.’ Many exoplanets have been found around stars that are nowhere near as metal-rich as our sun. According to DiStefano and Ray, it is true that Jupiter-sized planets are found more commonly around stars containing more heavy elements. But their research shows that Earth-sized planets “show no such preference,” according to a press release announcing the findings.
“It’s premature to say there are no planets in globular clusters,” says Ray.
There are other concerns. Mainly, all the other stars. The crowded area could increase the chances of a neighboring star getting too close and gravitationally disrupting a planetary system. This concern isn’t as large when you think about where the star’s habitable zone is. Many of the stars in globular clusters are red dwarfs. They are fainter stars, which means planets would have to orbit much closer to support life. This closer orbit would help protect it from any stray stars.
“Once planets form, they can survive for long periods of time, even longer than the current age of the universe,” says DiStefano.
Let’s say life is on one of these planets. And it did evolve into intelligent life. And it even evolved to where we are today. What would be different? A lot.
DiStefano describes it as the ‘globular cluster opportunity.’
“Sending a broadcast between the stars wouldn’t take any longer than a letter from the U.S. to Europe in the 18th century,” says DiStefano.
Interstellar travel would still be difficult, but a lot more feasible than it is for us. “The Voyager probes are 100 billion miles from Earth, or one-tenth as far as it would take to reach the closest star if we lived in a globular cluster. That means sending an interstellar probe is something a civilization at our technological level could do in a globular cluster,” she adds.
It’s interesting research, now we just need to find some more exoplanets in globular clusters. And that’s the tricky part. Finding transiting planets in a cluster’s core is nearly impossible. The best bet would be to look along the outskirts and hope you get lucky.
The Harvard-Smithsonian Center for Astrophysics offers another idea. SETI. They could look for radio or laser broadcasts in these globular clusters.
The globular cluster M13. Did you know we sent a signal to M13 in 1974? They won’t receive it for another 25,000 years. And we won’t hear a response for another 25,000 years.
For now, the question of ‘are we alone in the universe’ goes unanswered.