Twisting the Copernican Tail

The latest Carnival of Space offers several posts with an interstellar bent in addition to our own discussion, linked to from the Carnival, about antimatter rocketry and the recent thinking of JPL’s Robert Frisbee. I notice that Gerald Cleaver and Richard Obousy’s ideas about warp drive continue to get play, with particular reference to the amount of energy that this purely theoretical construct might demand. As with Alcubierre’s own warp drive speculations, the energy levels are daunting, in Cleaver and Obousy’s case the equivalent of converting the planet Jupiter into energy (that actually beats many Alcubierre demands!).

Thus NextBigFuture‘s comment, rising naturally from this conundrum:

…it makes no sense to assume being able to convert a planetary mass into energy without having increased control of technology and information and increased economy. It is like assuming a group of cavemen get the designs for a supersonic plane but only have the economy of their tribe of six to fund it. The assumptions would also be that they need to transport their rock caves and the woolly mammoths and buffalo herds that they hunt.

A point well taken, and one reason why blogger Brian Wang looks to laser propulsion as an alternative, a prospect that appeals to near-term thinkers because it takes us back into the realm of known physics. Moreover, in its various manifestations, beamed power leaves the propellant at home so that the spacecraft can carry a greater payload. What we need to learn, of course, is how sails behave in space, an examination we’ve yet to begin — let’s hope SpaceX can help us get the duplicate NanoSail-D package (whose existence was revealed in these pages) onto an upcoming Falcon flight. The ill-fated Cosmos sail built by the Planetary Society was itself capable of being used for microwave beaming experiments, and the sense here is that a world of useful experimentation awaits if we can just deploy that first true sail.

Mike Simonsen at Simostronomy takes a look at recent computer simulations from Edward Thommes and team that model planetary formation, with results that some have found unsettling:

What they found is that our solar system represents the rare cases, where gas giants form, but do not migrate to the inner planetary system, and the final orbits of the planets in the system are fairly circular and stable. In many simulations, lots of gas giants formed in chaotic environments with collisions and eccentric orbits. In other simulations, plenty of smaller rocky planets formed, but hardly any gas giants materialized out of the proto-planetary disk. Only under specific, unique conditions do planetary systems like ours evolve.

We’ve discussed the Thommes work with interest here, but failed to catch a National Science Foundation interview, in which the scientist described Earth-like planets as fairly common: “…they’re almost like weeds, they’ll sprout up under almost any conditions.” The uncommon aspect of our Solar System, then, is the existence of those gas giants in their particular orbits, posing the question of what happens to Earth-like worlds when gas giants migrate inward, as they seem to do in many simulations.

In a wider context, what happens if we do find out that a planet like ours really is rare? How would we cope with the overthrow of yet another paradigm, the Copernican perspective that has us constantly assuming we are living on an average planet in an average galaxy, and that given enough time we will inevitably find other intelligent species on similar worlds? Not that the Thommes team takes us anywhere near that conclusion, but it does offer a challenging look at planet formation theories that will only be confirmed or refuted once we have the resources in space to perform small exoplanet detections. And let’s just say it twists the tail of the Copernican assumption rather provocatively.

Star Formation in the Hinterlands

Centauri Dreams always thinks it’s important to talk about images like the one below. Not the specific subject matter — this is the Southern Pinwheel galaxy M83, about which more in a moment — but about the beauty of the image. Casual browsers of astronomy photos often tell me they never realized how colorful space actually is, which is why I want to say periodically that images like these are doctored to reveal information. In this case, far-ultraviolet light is intentionally shown in blue, near-ultraviolet light in green, and radio emissions — at the 21 centimeter wavelength of gaseous hydrogen — are shown in red.

M83 galaxy in false colors

Space is undoubtedly beautiful, but what you see in many of these photos is not what you would get if you were there. In fact, not only are the colors doctored here, but this is a composite image, incorporating observations from the Very Large Array and the Galaxy Evolution Explorer (GALEX), an orbiting ultraviolet survey telescope.

Image: The outlying regions around the Southern Pinwheel galaxy, or M83, are highlighted in this composite image from NASA’s Galaxy Evolution Explorer and the National Science Foundation’s Very Large Array in New Mexico. The blue and pink pinwheel in the center is the galaxy’s main stellar disk, while the flapping, ribbon-like structures are its extended arms. Credit: NASA/JPL-Caltech/VLA/MPIA.

So what would you see if you were actually viewing M83 from the viewport of an intergalactic spaceship? Greg Laughlin wrote up this question a few years back with regard to the Sombrero Galaxy, M104, noting that if you could somehow place yourself 300,000 light years from it, your human eyes would see a galaxy so dim that it would appear only as a faint, glowing patch. For that matter, try to see M31, the Andromeda Galaxy, subtending an angle larger than the full Moon in the sky, and you’ll see precisely nothing there. Laughlin describes this key fact:

The storms from earlier this week have blown through. The sky sparkles with brilliant clarity. Yet when I step outside and look up, I can’t see the Andromeda Galaxy at all. It’s too faint. In a 1:10,000,000,000,000 scale model of M31, the stars are like fine grains of sand separated by miles. Our Galaxy, the Andromeda Galaxy, and the Sombrero Galaxy are all essentially just empty space. To zeroth, to first, to second approximation, a galaxy is nothing at all.

All of which is prelude to the real point of this post, which is that the image above lets us see things we would otherwise find invisible, in this case the Southern Pinwheel galaxy itself and the extended galactic arms in which astronomers have now identified new stars forming. Their distance from the primary disk of M83 is impressive, even startling, for M83 is only some 40,000 light years across, while the young star formation area runs up to 140,000 light years away from the center of the galaxy, a phenomenon Frank Bigiel (Max Planck Institute for Astronomy) calls ‘absolutely stunning.’

Shouldn’t these galactic outskirts be deficient in star-forming materials? You would think so, but the radio observations from the Very Large Array pinpointed the location of the necessary hydrogen, findings that mesh with what the Galaxy Evolution Explorer saw. Thus we may be looking at the kind of star formation that occurred early in the history of the cosmos, when dust and heavier elements were not plentiful. That makes M83, some 15 million light years away in the constellation Hydra, a helpful proving ground for our theories of early star formation, as per this GALEX news release. Such a relatively nearby laboratory (in cosmic terms, at least) will help us develop useful data for comparison with what we see much further out in space and, by extension, back in time.