# How could a civilization trigger star formation?

I'm going for the ultimate in world building here: Creating a whole new star.

I have a race that's about a Type II civilization (as per the Kardashev scale). The important thing here is that they're capable of building megastructures, such as a Death Star. They could build a Dyson Sphere or something on that scale, but it would be extremely hard.

For some reason, this civilization wants to make a star in the middle of a giant molecular cloud, which is a large interstellar cloud composed of gas (molecular $H_2$) and dust where young stars are born. For a star to be born, a section of this cloud has to undergo gravitational collapse.$^1$

Scientists (in our world) don't know for sure what triggers this collapse, but there are some ideas. One is that a supernova shockwave hits the cloud. Another is that two clouds collide and collapse.

How can this civilization trigger any of these events and form a star? Is it even possible?

Note: A food page to look at is the Wikipedia page on Jeans instability. That might help you come up with an idea, if you can figure out what quantities need to change.

$^1$ You could just add matter, but I'd like to avoid that.

• I would guess your best bet would be to seed the cloud, like we can for rain... Jan 21, 2015 at 16:44
• @bowlturner With what? Are you suggesting mass injection? Jan 21, 2015 at 16:45
• well yes. Though I know you don't want that. Unless you can generate a (very large) gravity field... Jan 21, 2015 at 16:46
• That "giant molecular cloud" is aka a "nebula" Jan 21, 2015 at 17:34
• There are about 100,000,000,000 stars in the galaxy, ready-made, with new ones forming naturally all the time in a galaxy like ours. Why do you need to make a new one? Jan 21, 2015 at 21:07

Ok, I'll bite. If all you got in the area is a big cloud, mostly Hydrogen, with teensy amounts of heavies scattered about, and you're getting chilly, or wanna cook s'mores, and you need a New Star there toot sweet, as Granny Ogg would say, what can you do?

Above: Very Rude Nebula. Basically asking to be subjected to some serious fusion.

1. You could blow up (turn super?-nova) a nearby star you don't like. I hear that take a bit of energy. Likely beyond a Type II.

2. Find a nearby inactive black hole, feed it some hapless dwarf and point the jet at the cloud. Iffy.

3. Build giant megastructures to generate huge magnetic fields and direct the gas in a large area.

4. Get overthrown in a rebellion by the overtaxed populace asking why you're spending their hard-earned Joules on acts of cosmic vandalism like setting molecular clouds on fire. They will banish you to the center of a molecular cloud. As a dense massive object, your (soon to be inanimate) body will slowly attract nearby gas molecules. Over time, your body will become the accretion center for a new star.

• +1 for Terry Pratchet reference! Also, laughed more than I should at point 4. Jan 22, 2015 at 8:47
• +1 for the great picture of the en.wikipedia.org/wiki/Carina_Nebula Jan 22, 2015 at 13:07
• Damn, you're funny. +1 for the humor; acceptance because these would seem to work. Jan 22, 2015 at 16:02

If you've got a death star, why not park it for a few centuries/millenia in the middle of the gas cloud?

Better yet, store all of your death stars in the middle of the gas cloud when they're not in use. Their gravity will help compress the gas cloud which will in turn increase the internal gravitational force it exerts on itself. Once the gas cloud is proceeding nicely towards stellar formation, and the center of the cloud is generating enough gravity to get it the rest of the way on its own, fly the death stars off to the next cloud of gas to create the next star.

Set up a large number of large thermonuclear bombs in a sphere around the correct mass for the star you wish to create and explode them simultaneously. This will create two roughly spherical shock waves one travelling toward the center of the sphere, another away from it. If the explosion was powerful enough to overcome the pressure of the gas cloud, the shock wave travelling towards the center will not stop until it has compressed the gas enough for it to collapse on its own gravity and form a star.

• “large” thermonuclear bombs? Sounds like it takes exploding stars to create new stars on demand. Aug 22, 2016 at 7:17
• @JDługosz The scale is certainly like that, but the amount of energy needed would be much smaller. With exploding stars only incidental amounts go towards creating concentrations of mass and vast amounts go towards dispersing surrounding gas. With "stellar engineering" nearly half of energy would go towards compression, I think. Aug 24, 2016 at 6:36

Build a really big ramscoop (a set of magnetic fields that funnel material toward a central point):

http://en.wikipedia.org/wiki/Bussard_ramjet

But reduce constriction so you don't actually achieve fusion. For propulsion use whatever it is that you're already doing as a type II civilization. Now the end result of running your ship through the GMC will be compressed "strings" of material, but it's still the H2 that you want to build your star out of.

By running the ship in several tight loops (think a spring or slinkie) you should be able to create enough of a clump that it will start pulling together under it's own gravity. Over time it will pull in more of the cloud and eventually turn into a star.

I am not well versed enough in the physics to be sure, but you might have to do several clumps to get your target stellar mass (assuming they'll eventually fall into eachother).

Physics: If there's a black hole nearby which is spewing out a powerful jet, the civilization could "just" redirect that jet to compress the cloud. By flipping the black hole sideways or setting up a ramscoop as proposed by Dan Smolinske.

Chemistry: The cloud is not collapsing because its pressure counteracts gravity. A "death star size" machine produces a cloud of particles which reacts endothermically with elements in the cloud (possibly as a catalyst, to reduce the amount of material produced). This cools the cloud, reducing the pressure. Alternatively, the new molecules have new degrees of freedom so that radiation can be absorbed as say rotation of the molecule, or they are able to radiate heat more efficiently in the infrared frequencies in which the cloud is transparent. All this reduces the kinetic energy of the cloud particles, reducing pressure and allowing it to contract.

Pulse X-Ray, Gamma and other high energy laser beams at precisely calculated areas of the cloud, ionizing the gas molecules that the beam passes through - ion attraction will condense those areas and eventually lead to stellar formation. (Ironically) Solar sail equipped magnetic field generators sailing through the cloud would also accelerate the condensation process in a largely automated process.

If we assume you have access to some kind of anti-gravity and artificial gravity technology, then just stick a gravity generator in the cloud, turned on to its maximum setting, and wait a few thousand years.