Orion Nebula Research: Habitable Planets Could Be Rarer than Thought

Dave on Earth (5:02 PM): Hi Josh, Dave Mosher from Discovery Space on this end.

StarClusterGuy (5:03 PM): Hi Dave.

Dave on Earth (5:04 PM): I'm in New York right now -- where are you typing from?

StarClusterGuy (5:05 PM): I'm In Berkeley, California. Supposed to get up to 90 degrees today here. And we don't have air conditiong.

Dave on Earth (5:05 PM): Well if you stop responding to my questions, I suppose I'll just assume you fainted.

StarClusterGuy (5:06 PM): It isn't often this hot... But today it is. That and we have an old building, which doesn't help.
Speaking of hot things, we've been looking at the Orion Nebula cluster, which is one of the mostly densely populated star-forming regions in our neighborhood.
That "neighborhood," by the way, is about 1,000 light-years away from us.

Dave on Earth (5:09 PM): You said "densely populated." Obviously you're not talking about aliens here...

StarClusterGuy (5:11 PM): Nope! It has hundreds of stars packed into a space a few light-years on a side -- about the radius from the sun to the nearest star.
The Orion cluster also has some very massive stars (the well-known Trapezium stars) that bathe the region in intense radiation.

Dave on Earth (5:14 PM): So you could probably get a tan a lot faster if you were hanging out in the Orion cluster...

StarClusterGuy (5:14 PM): Probably in a few seconds.
It's deadly, but we think that our own sun -- and Solar System -- formed in a region a lot like that billions of years ago.

Dave on Earth (5:14 PM): Let's say you were standing on a planet in the center of Orion right now.
What would it look like staring out into the sky around you?

StarClusterGuy (5:16 PM): It'd be hard to survive for long, thanks to all of the intense radiation.
But ignoring that, I imagine that the sky would be in full daylight, with many suns all of the time.
It would be blindingly bright.

Dave on Earth (5:17 PM): Hmm... so how did we get from over-baked to just right like we are now?

StarClusterGuy (5:18 PM): Orion is dense now, and its stars are held together by lots of gas still hanging around.
However, stellar winds and supernovae explosions will push that material around.
And soon the cluster won't have enough gravity to stay together -- this is probably what happened to the cluster in which our sun is thought to have formed.
In fact, this seems to be the fate of most big clusters.

Dave on Earth (5:20 PM): So hot, dense clusters aren't necessarily a whack for the potential of life.
But you're the lead author on a new study, and I believe that you found that planetary systems like our own are rarer than previously thought...

StarClusterGuy (5:22 PM): We found that most Orion stars aren't surrounded by enough debris to form Solar Systems like ours.
Take a Jupiter-sized planet, for example. You need about 1/100th of the sun's mass of dust and gas to make it.
Well, we found that less than 10 percent of the stars in Orion have circumstellar disks big enough to do that, and Orion-like regions are where most stars in the Galaxy form -- including ours.

Dave on Earth (5:23 PM): Circumstellar disks -- you mean disks of gas and dust?

StarClusterGuy (5:23 PM): Yes. Young stars are surrounded by disks of dust and gas, remnants of the early phases of star formation.
In other words, the building blocks of planets.

Dave on Earth (5:25 PM): You said that big, gassy planets like Jupiter might be rarer than we previously thought. What about Earth-sized planets?

StarClusterGuy (5:27 PM): Our results don't constrain the existence of Earth-sized planets, since they're smaller and require much less dust and gas for their formation.
In fact, the average star in Orion is surrounded by at least some circumstellar material -- probably enough to build Earth-like planets.

Dave on Earth (5:29 PM): So the search for Earth-like planets out there isn't doomed, after all?