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The Star as Starship

Moving entire stars rather than building spaceships would have certain benefits as a way of traveling through the galaxy. After all, it would mean taking your local environment with you on a millennial journey. Some have suggested it might therefore be an observable sign of highly advanced civilizations at work. But how would you move a star in the first place?

In Bowl of Heaven (Tor, 2012), Gregory Benford and Larry Niven conceive of a vast bowl — think of one-half of a Dyson sphere — wrapped around a star whose energies are directed into a propulsive plasma jet that, over aeons, moves the structure forward. Thus this snippet of dialogue, said aboard a starship by the humans who discover the alien artifact:

“…You caught how the jet bulges out near the star.”

More hand waving. “Looks to me like the magnetic fields in it are getting control, slimming it down into a slowly expanding straw…”

“A wok with a neon jet shooting out the back…and living room on the inside, more territory than you could get on the planets of a thousand solar systems. Pinned to it with centrifugal grav…”

“They don’t live on the whole bowl. Just the rim. Most of it is just mirrors. Even so, it’s more than a habitat,” said Cliff. “It’s accelerating. That jet? This whole thing is going somewhere. A ship that is a star. A ship star…”

The Benford/Niven excursion into mega-engineering came to mind over the weekend when I read Keith Cooper’s recent article for the Institute for Interstellar Studies on the ideas of Fritz Zwicky. The wildly creative astrophysicist (1898-1974) once imagined a scheme that would use the Sun as an engine that could propel us — and I do mean all of us — to Alpha Centauri. The notion was to induce ‘hot spots’ in the solar photosphere that would lead to asymmetrical flares, nudging the Sun in a new direction. Zwicky imagined that the recoil of these directed exhaust jets would make an interstellar crossing in about fifty centuries possible, pulling the Earth along with our parent star.

In a lecture in 1948, Zwicky referred to ideas like these as ‘morphological astronomy,’ which he would go on to discuss in detail in his 1969 book Discovery, Invention, Research Through the Morphological Approach, a title that ranges over everything from telescope design to aerodynamics and the concept of justice. But as Cooper notes, a number of questions are left unanswered, including details of the asymmetric thrust mechanism itself, and the always interesting question of deceleration. Just how does the Sun approach Alpha Centauri, and what effects would the move have on solar planets as well as those around the destination stars?

If a highly advanced civilization did have the ability to engineer stellar acceleration, we might spot its efforts through unusually high proper motions of particular stars. So-called ‘hypervelocity stars’ have been observed that appear to be gravitationally unbound to the Milky Way. In fact, Kelly Holley-Bockelmann and Lauren Palladino (Vanderbilt University) have identified 675 stars that were probably ejected from the galactic core, presumably because of gravitational interactions with the supermassive black hole at galactic center. Moving at velocities as high as 900 kilometers per second, stars like these would take 10 million years to travel from the core to the outer edge of the spiral. The stars in question tend to be red giants with high metallicity. Later work at Ohio State has identified a small number of hypervelocity stars with masses closer to that of the Sun.

hypervelocity stars

Image: Hypervelocity stars zoom around the center of the Milky Way, where a supermassive black hole lurks. Credit: ESO/MPE.

Cooper asks whether stars with anomalous proper motion might not be worth investigating in a SETI context. From his essay:

Perhaps some advanced extraterrestrial civilisation out there has that power. Maybe we should look to stars with anomalously large proper motions. Is Barnard’s Star, which has the highest proper motion of any star in the sky at 10.3 arcseconds per year, at its distance of 5.98 light years, simply a refugee ejected from a binary star system or is it being deliberately driven? Astronomers even observed a giant flare on the star in 1998, which reached temperatures as high as 8,000 degrees Celsius, which is 2,500 degrees Celsius hotter than the Sun’s surface, or photosphere. Given that Barnard’s Star is a red dwarf with an average surface temperature typically languishing at 2,860 degrees Celsius, that’s a heck of an increase. Now, I’m not suggesting that extraterrestrials are using Barnard’s Star as a spacecraft, only that should such a feat be possible (and that’s a big if), we might expect it to look something akin to the speeding red dwarf.

The idea of moving entire stars as a means of interstellar travel is intriguing and might fall into our toolbox of ideas on ‘interstellar archaeology,’ the search for unusual artifacts in our astronomical data. After all, moving a star simply ramps up an already existing process. We’re all on a grand tour through the Milky Way as the Sun moves at a brisk 220 kilometers per second in its orbit. An advanced civilization with clearly defined destinations in mind might find random encounters with other stars less interesting than targeted travel.

The paper on hypervelocity stars is Palladino et al., “Identifying High Metallicity M Giants at Intragroup Distances with SDSS,” The Astronomical Journal Vol. 143, No. 6 (May, 2012), p. 128 (abstract / preprint).


Comments on this entry are closed.

  • James D. Stilwell November 25, 2013, 12:09

    I’d love to know what all of you think about Star Trek’s ‘Q’….Surely no more a feat that converting a star into a starship engine….or are we sliding into the realm of angels and devils….

  • A. A. Jackson November 25, 2013, 12:51

    There is a paper
    “Possibility of controlling solar system motion in the galaxy”, Solar System Research , vol 22, #4, 1989 by Dr. Leonid Mikhailovich Shkadov (actually presented in 1987 , published in Russian in 1988) about moving the solar system. One builds a huge reflector around the sun and uses radiation pressure to move it.
    Quite to my surprise there is a Wikipedia article on this called “The Stellar engine”!


    Follow the links and one finds later papers , by others , in the JBIS.
    What I thought was a forgotten paper has a following, I should have known.

    I am guessing , but don’t know for sure, Larry Niven’s Pierson’s Puppeteers moving their home planetary system, see Fleet or Worlds, predates this idea but I can’t remember Niven giving a mechanism.

  • Paul Gilster November 25, 2013, 13:33

    I touched on Shkadov briefly in a recent piece for Aeon Magazine:

    “That such could exist takes us back to 1948, when astronomer Fritz Zwicky began to speculate on how civilizations older than ours might use their powers. One possibility: Firing fuel pellets into the central star to move an entire solar system to a new location, in effect touring the galaxy without leaving home, perhaps motivated by an upcoming encounter with dense interstellar dust, or conceivably driven by sheer curiosity. Physicist Leonid Shkadov would suggest forty years later that huge spherical mirrors could be built to do much the same thing, creating a feedback effect from the star’s radiation to take control of its trajectory through the galaxy.”

    Can’t say I’ve explored his ideas more than briefly, which gives me an idea for a future article here.

  • Michael November 25, 2013, 14:15

    I might be possible for a spacecraft to wait near a Star and then deploy a sail at the right moment to ride a CME.

  • Jonathan Vos Post November 25, 2013, 15:00

    I have written extensively on the IDEOCOSM and its systematic exploration, as described in Discovery, Invention, Research Through the Morphological Approach.

  • Adam November 25, 2013, 16:20

    Of course the first discussion of moving stars for intergalactic travel would be Olaf Stapledon’s depiction in “Star Maker” (1937). The Galactic Community attempts to redirect a whole star system to a neighbouring galaxy – unfortunately for the system’s inhabitants, the star has other ideas and reacts violently. Stars, it seems, co-ordinate their orbits in a vast Dance, which means any unnatural orbit change is seen by them as a violation. Whether Stapledon’s idea of intelligent stars is at all viable is a different discussion, but the various hypervelocity stars suggest that natural stars aren’t overly worried about leaving their natural orbits.

    Perhaps sufficiently advanced civilizations arrange for hyper-velocity encounters for white dwarfs, with close orbitting planets, to then fly to other galaxies. If a white dwarf habitable zone is stable for ~8 billion years, then 0.01c would mean a range of ~80 million light-years.

  • David Cummings November 25, 2013, 17:09

    Here’s an interesting article about the current motion of our sun. It looks like we are moving more slowly than originally thought (with respect to the galactic environment), and it also seems that slower is better in terms of in-system protection from cosmic rays.


  • Adam November 25, 2013, 17:42

    BTW the Hyper-Velocity planet paper is here: Hypervelocity Planets and Transits Around Hypervelocity Stars

  • CharlesJQuarra November 25, 2013, 17:48

    How would you reduce or brake the fusion process in a Star? What if you are a civilization that is very future-conscious, and wants to extend the lifetime of the star’s fuel as far in the deep future as their technology permits?

    A way is to take a part of the emitted power, refocus it into the surface and produced a flare that via some undetermined nonlinear effects locally exceeded the Eddington limit. Then one would store the ejected material in a gas disk surrounding the star, keeping it into an orbital ring for easy capture (low delta-V), but somehow disrupting the turbulent instabilities ( http://en.wikipedia.org/wiki/Kelvin–Helmholtz_instability ) that, if left to its own devices, would eventually grow and turn the ring into a gas giant

    Now, my question is: how would we distinguish this kind of gas storage rings from protoplanetary rings? One possibility is that the ring chemical composition should exactly match the composition of the star’s outer layers.

    What other possible clues one can extract that can suggest or reject the technological origin of a gas ring?

  • stephen November 25, 2013, 17:52

    I remember the suggestion of sending solar material out through either the north or the south magnetic pole of the star.

    Wouldn’t interstellar debris be a problem, causing too many impacts on the planets?

    How much of the star’s mass would be consumed to accelerate it near lightspeed?

  • Adam November 25, 2013, 18:29

    Charles, how would you stop gas pick-up by the stellar wind? Storage requires something better than a mere ring.

  • Eniac November 25, 2013, 22:47


    How much of the star’s mass would be consumed to accelerate it near lightspeed?

    Nearly all of it. And unless you could ramp up energy release up enormously (which, in effect, would be a controlled supernova), it will take billions of years to get up to speed. Not a way to travel for the impatient.

    Let’s stick with ships, just saying…..

  • NS November 26, 2013, 2:15

    Since approaching another star might be very disruptive to our solar system (and theirs, if any) it seems as though it would make more sense to use stellar acceleration to move AWAY from other stars (or black holes etc.) rather than toward them.

  • Brett Bellmore November 26, 2013, 6:58

    “How much of the star’s mass would be consumed to accelerate it near lightspeed?”

    Essentially all of it, the delta V is doubtless better than chemical rocketry, but poor compared to a straighforward fusion rocket, and that would need a huge mass ratio to get to relativistic speeds.

  • David Cummings November 26, 2013, 10:10

    Hard to turn, hard to stop, unable to get too terribly close to a destination star for fear of unwanted gravitational entanglements, leaving you still with the problem of actually traveling from earth to an exoplanet.

    I’m not saying it will never be considered, especially if it turns out there is a more desirable galactic neighborhood… But it geeks to me it will be more like moving and less like travel. I think the travel will still be done in ships and the travel will precede the move by many millennia.

  • Michael November 26, 2013, 13:42

    “How much of the star’s mass would be consumed to accelerate it near lightspeed?”

    Half, One half at near the speed of light in the other direction is needed to conserve momentum if they travel at the same speed.

  • Michael November 26, 2013, 13:45


    I case you missed it I have responded to your reply in ‘Two Ways to the Stars’

  • Brandon Bowers November 27, 2013, 9:07

    In terms of efficiency it’s better to move the rest mass of the intellects considering colonization to the target resource matter than to attempt to move the entire solar system to the target resource matter.

    Of course in the interests of efficiency we could use stellar engineering to lift matter out of the Sun and create new red dwarfs, accelerate those out beyond Pluto and then generate solar systems locally to colonize.

    Figure 1.4% of the Sun’s mass to spawn a brown dwarf and a few terrestrials and you have a small dim sister solar system that will last for a million years or so. Once they burn out (run out of deuterium), move the planets around and combine 4-5 of them into a red dwarf that ignites (.08 Solar MAsses or so) and then you have a star that will burn for 10-14 trillion years.

  • stephen November 27, 2013, 10:59

    A civilization might find a binary pulsar, or whatever it is which produces those mysterious gamma-ray bursts, and use the energy from that system to move the system away from the rest of their civilization.

    Yeah, I figured it would take most of a star’s mass to get it to near lightspeed, but if it’s supermassive, it’s going to be a supernova, they’d want to move it away from their home system(s), and use what’s left over as an energy source for whatever habitats they have orbiting that star.

    But once it’s far enough away not to be a threat, it’s mass will be reduced so much it won’t be a supernova anymore. Oh, well, at least they have an energy source for their habitats…

  • Eniac November 28, 2013, 12:39

    As someone else has hinted at, the only conceivable use of this scheme would be intergalactic colonization. In just a few million years, our descendants might find themselves in a fully occupied galaxy, and they may by then have found that other galaxies seem devoid of life. They might find this depressing enough to rig up a few star systems and put them on a trajectory that will intercept other galaxies in a couple of billion years. Think of it as the grandest effort to spread life and civilization, ever.

  • ljk December 5, 2013, 0:11

    Figures of Eight and Peanut Shells: How Stars Move at the Center of the Galaxy

    November 27, 2013

    Two months ago astronomers created a new 3D map of stars at the centre of our Galaxy (the Milky Way), showing more clearly than ever the bulge at its core. Previous explanations suggested that the stars that form the bulge are in banana-like orbits, but a paper published this week in Monthly Notices of the Royal Astronomical Society suggests that the stars probably move in peanut-shell or figure of eight-shaped orbits instead.The difference is important; astronomers develop theories of star motions to not only understand how the stars in our galaxy are moving today but also how our galaxy formed and evolves.

    The Milky Way is shaped like a spiral, with a region of stars at the centre known as the “bar,” because of its shape. In the middle of this region, there is a “bulge” that expands out vertically.In the new paper Alice Quillen, professor of astronomy at the University of Rochester, and her collaborators created a mathematical model of what might be happening at the centre of the Milky Way.

    Unlike the Solar System where most of the gravitational pull comes from the Sun and is simple to model, it is much harder to describe the gravitational field near the centre of the Galaxy, where millions of stars, vast clouds of dust, and even dark matter swirl about. In this case, Quillen and her colleagues considered the forces acting on the stars in or near the bulge.

    Full article here:


  • bob December 10, 2013, 14:12

    i think we can build artifical sun on earth orbit and move earth from the solar system if we corect calculate orbit we can have 270km/s (sun speed + earth speed ) with this speed we fly distance one light year in ca.1100year but we can speed up so earth be movin faster and faster and moving earth be much more easy than move sun

  • ljk January 14, 2014, 23:09

    Kugelblitz! Powering a Starship With a Black Hole


    Jeff Lee, Researcher for the X-Physics, Propulsion and Power group of the nonprofit research organization Icarus Interstellar discusses the possibility of starship powered by black holes.

    Interstellar flight certainly ranks among the most daunting challenges ever postulated by human civilization. The distances to even the closest stars are so stupendous that constructing even a scale model of interstellar distance is impractical. For instance, if on such a model, the separation of the Earth and sun is 1 inch, the nearest star to our solar system (Proxima Centauri) would be 4.3 miles away!

    The fastest object ever built by the human species is the Voyager 1 space probe, moving at a speed of 18 miles per second. If it were heading toward Proxima Centauri (which it’s not), Voyager 1 would reach our nearest stellar neighbor in about 80,000 years.

    Full article here: