Globular clusters could host interstellar civilizations

January 6, 2016
The Messier 80 globular cluster in the constellation Scorpius is located about 30,000 light-years from the Sun and contains hundreds of thousands of stars. Credit: NASA

Globular star clusters are extraordinary in almost every way. They're densely packed, holding a million stars in a ball only about 100 light-years across on average. They're old, dating back almost to the birth of the Milky Way. And according to 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," says lead author Rosanne DiStefano of the Harvard-Smithsonian Center for Astrophysics (CfA).

DiStefano presented this research today in a press conference at a meeting of the American Astronomical Society.

Our Milky Way galaxy hosts about 150 , most of them orbiting in the galactic outskirts. They formed about 10 billion years ago on average. As a result, their 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 (Tata Institute of Fundamental Research, Mumbai) argue that this view is too pessimistic. Exoplanets have been found around stars only one-tenth as metal-rich as our Sun. And while Jupiter-sized planets are found preferentially around stars containing higher levels of , research finds that smaller, Earth-sized planets show no such preference.

"It's premature to say there are no planets in globular clusters," states Ray.

Another concern is that a globular cluster's crowded environment would threaten any planets that do form. A neighboring star could wander too close and gravitationally disrupt a planetary system, flinging worlds into icy interstellar space.

However, a star's habitable zone - the distance at which a planet would be warm enough for liquid water - varies depending on the star. While brighter stars have more distant habitable zones, planets orbiting dimmer stars would have to huddle much closer. Brighter stars also live shorter lives, and since globular clusters are old, those stars have died out. The predominant stars in globular clusters are faint, long-lived red dwarfs. Any potentially habitable planets they host 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.

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.

Such a civilization would enjoy a very different environment than our own. 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 U.S. to Europe in the 18th century."

"Interstellar travel would take less time too. 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.

The closest globular cluster to Earth is still several thousand light-years away, making it difficult to find planets, particularly in a cluster's crowded core. But it could be possible to detect transiting planets on the outskirts of globular clusters. Astronomers might even spot free-floating through gravitational lensing, in which the planet's gravity magnifies light from a background star.

A more intriguing idea might be to target globular clusters with SETI search methods, looking for radio or laser broadcasts. The concept has a long history: In 1974 astronomer Frank Drake used the Arecibo radio telescope to broadcast the first deliberate message from Earth to outer space. It was directed at the globular cluster Messier 13 (M13).

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15 comments

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TheGhostofOtto1923
2.8 / 5 (9) Jan 06, 2016
Well maybe globulars were actually created by advanced cultures as extremely desirable places to live. Short travel distance among stars, little gas or debris, no supernovae, nice quiet, stable stars.

They couldn't be better places to live if they had been designed for the purpose.
TheGhostofOtto1923
2.8 / 5 (9) Jan 06, 2016
AND if they predate the galaxies they orbit, maybe the civilizations within them were responsible for constructing these galaxies. Why? To counteract the effects of dark energy and preserve islands of matter for as long as possible while everything else disappears into the void.

The older a civilization would be, the farther into the future their plans would extend.

And the more likely that they would consist of machine singularities.
Whydening Gyre
5 / 5 (4) Jan 07, 2016
Well maybe globulars were actually created by advanced cultures as extremely desirable places to live. Short travel distance among stars, little gas or debris, no supernovae, nice quiet, stable stars.

They couldn't be better places to live if they had been designed for the purpose.

Kinda like the Hamptons, eh?:-)
Psilly_T
5 / 5 (1) Jan 08, 2016
fun and non boring ideas otto :)
geokstr
3 / 5 (4) Jan 08, 2016
...since globular clusters are old, those stars have died out.


Honest question: Stars don't just "die out", do they? Aren't all deaths of stars violent nova/supernovas?

If so, might not at least the more central stars be higher in the heavy elements than the average content in the overall cluster as second generation stars? Thanks in advance for any enlightenment.

Oh, also, are organic molecules found in quantity in any of the clusters? They seem to be pretty much everywhere.
Uncle Ira
3.7 / 5 (6) Jan 08, 2016
Stars don't just "die out", do they? Aren't all deaths of stars violent nova/supernovas


Only the ones that 1.4 times the sun size after they get done blowing all the stuffs away when they are puffed up giants in their old age. Our sun star is not big enough to be a supernova because he is too small. He'll end up as the white dwarf and sooner or later cool down to a ash hunk.

Imight not at least the more central stars be higher in the heavy elements than the average content in the overall cluster as second generation stars


The newer ones will have more metals in them than really older ones.

Thanks in advance for any enlightenment

Don't thank me too much because it is really good chance I am messing up what I read.

are organic molecules found in quantity in any of the clusters

I have not read about that so I don't have any idea. Maybe Techno/Maggus/Capt/Furlong or aa-Skippys will come along so you don't get the crankpot answer.
Uncle Ira
3 / 5 (4) Jan 08, 2016
P.S. for you geo-Skippy. You sure do ask the question like a gentleman, you set the good example you.
HeyChief
5 / 5 (1) Jan 11, 2016
The Voyager probes are about 10 billion miles distant ( not 100 billion as stated), thus making hypothetical star to star intraglobular cluster travel (at V-probe speeds) a factor of ten longer of a journey - pack more rolls of toilet paper on that trip.
antialias_physorg
4.3 / 5 (6) Jan 11, 2016
I wonder how stable planetary systems are in a globular cluster. After all you have to contend with the occasional neighboring star being on a close flyby. That might disrupt planetary orbits quite a bit. maybe not enough to make planetary systems impossible but by gut feeling I'd think that planets so affected don't exhibit the kind of stable/sheltered conditions needed for life to evolve.

Only the ones that 1.4 times the sun size

And those are the vast minority of stars. Still, with many stars in the vicinity even one such event could spell doom for life in a quite a few close-by systems.

Dunno about metallicity distributions in clusters. I only find papers for metallicity distributions accross clusters. Pretty sure organics are all over the place just like everywhere eles, though. No reason why they shouldn't be.
bluehigh
2.3 / 5 (3) Jan 11, 2016
Good comments Otto. You've let your cognitive ability kick in and refocused.

However ..

* Short travel distance among stars, *

> The stars are closer than you believe. ( Shields up .. IMHO)

bluehigh
1.6 / 5 (7) Jan 11, 2016
And Aniti-Thinking is still searching and reading papers to validated years of brain washing.

Silly old fart.

my2cts
3.7 / 5 (3) Jan 13, 2016
And Aniti-Thinking is still searching and reading papers to validated years of brain washing.

Silly old fart.


What a stupid post. Shame on you.
bluehigh
1.7 / 5 (6) Jan 13, 2016
my2cts, you are another misanthrope with a persistent negative attitude toward any new ideas.

Better an occasionally stupid post rather than be a complete imbecile like you.

How's the view looking in your own arse hole, you sick piece of shit.

Piss off and let the open minded discuss science.

viko_mx
2 / 5 (4) Jan 13, 2016
I'm afraid that is not yet born а man who is able to explain how can be formed the cosmic structures thanks to gravity, which is not able to stop the hypothetical expansion of the universe and the moving away galaxies claimed by theorists of cosmic evolution. O the rotation of the cosmic structures in different directions.
my2cts
3 / 5 (2) Jan 13, 2016
my2cts, you are another misanthrope with a persistent negative attitude toward any new ideas.

Calling someone a "silly old fart" now is a new idea? And who is th emisanthope here?

Better an occasionally stupid post

So you do admit it was a stupid post
rather than be a complete imbecile like you.

There another indication that you don't like people.
How's the view looking in your own arse hole, you sick piece of shit.

Piss off and let the open minded discuss science.


Hark the brilliant mind who will solve all great problems of science, sure.

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