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Nomad Planets: Stepping Stones To Interstellar Space?
An anonymous reader writes "Ian O'Neill suggests in an opinion piece at Al Jazeera that brown dwarves and nomad planets (planets not orbiting any star) could be a much needed stepping stone on our way to foreign stars. Quoting the article: 'In February, a fascinating paper was published in the Monthly Notices of the Royal Astronomical Society detailing calculations on how many "nomad planets" the Milky Way must contain after estimating our galaxy's mass from how much gravity it exerts on surrounding space. Scientists from the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) had uncovered something surprising — there are likely many more planets in the Milky Way than stars. ... Louis Strigari and his Kavli team calculated that there must be 100,000 planets for every star in the Milky Way (PDF). That's a lot of planets! But how can this be? Every star can't have tens of thousands of planets ranging from Pluto-sized to Jupiter-sized. This planetary "excess" actually suggests the existence of planets that were born without a star — nomad planets. ... we need all the help we can get if we are to venture to another star, so these ultracool brown dwarfs could become much-needed "stepping stones" for future starships to refuel on their light-years of journey time. There may be the possibility that these sub-stellar objects may even become more desirable targets for interstellar travellers. After all, there may be dozens of these invisible objects between here and Proxima just waiting to be uncovered by the sophisticated infrared telescopes of the future; they'd certainly make for more accessible scientific curiosities.'"
Sounds like they're hypothesising that all the "dark matter" is actually made of planets, or did i miss something...
Also - frist prost!!!
Al Jazeera that brown dwarves and nomad planets
I see what you did there.
When did a light year become a unit of time?
I don't think I'd want to stop at some random dwarf star. What is it you don't want on a long trip? Yes, to slow down and enter another gravity well. Doing so would make for a hell of a long trip. The time spent accelerating back along your path (people used to call it decelerating, but apparently that isn't a correct term), the fuel used escaping from the new gravity well, and the time and fuel used accelerating again. Worth it? Maybe if your design requires all that refueling. But the time involved is going to be the killer. It would probably triple (or more) the duration of the trip.
Sounds like they're hypothesising that all the "dark matter" is actually made of planets, or did i miss something...
DM cannot be made of planets because it cannot be made of atoms (it was not part of the plasma which filled the universe ~380k years after the Big Bang) nor does it have the same distribution as matter in a galaxy (rather than a disc it forms a spherical halo). The "gravitational effect" the summary misleading refers to is not the gravitational field of the galaxy but the local gravitational field of the object which bends light creating a lens effect. If the object passes between us and a distant star then the field will bend more light towards us causing the star to get brighter which is how you can detect them without seeing them.
The estimate while not based on a lot of evidence, does have a rational basis. The authors are using a power law model and estimates of large nomads (objects above the mass of Jupiter through to brown dwarf mass) from microlensing events to give a crude estimate for the population of planets down to Pluto size. It's shaky, but not unreasonable given that asteroids follow the same power law distribution, for example.
Well, the paper actually claims that there are between 2x and 100000x the number of nomad planets as there are stars. This kind of conservative claim is almost certainly right! Their ability to count on the press to distort their claims by citing only the upper bound and not the lower bound is canny and borderline unethical. Kudos to them for an excellent piece of press-release science!
A similar concept, the colonization of trans-neptunian objects, and effectively colonizing in a ladder out of our star system and down into other ones by rock hopping is also quite old. Sagan and others were talking about this a long time ago.
Here's the best starship concept I have come up with, based upon the assumption that there are no major undiscovered principles of physics. (aka no way to cheat basic material science or travel faster than light or cheat conservation of momentum, and relativity holds)
Technology needed : with a form of nanotechnology known as "molecular manufacturing", you can produce anything of any size with control over every atomic bond. The only limits are materials and energy. You can also deconstruct any frozen object and determine it's molecular structure.
For departing Sol, use mass drivers. Either build a gigantic mass driver that can accelerate the entire starship in one go, or give the starship a mass driver that can "catch" pellets of iron fired from a smaller one you leave back at Sol.
Either way, you want to accelerate to the desired speed as rapidly as possible. This means hundreds or thousands of Gs of acceleration. The ship is mostly solid state at this point.
At 90% of the speed of the light, the ship cruises until it gets close enough to the destination star. At this point, it reconfigures the matter about the ship into a bussard ramscoop and uses this as a brake to slow down. This way, you use free floating interstellar particles as the reaction mass instead of mass carried aboard the ship. Antimatter is used as a power source, the antimatter being burned inside a power reactor inside the ship. (antimatter does not work very well as a direct source of propulsion)
The same nanotechnology used to construct the ship can also conduct perfect repairs and quickly respond to damage (given sufficient materials and energy). That way, during the many years of travel time when the ship is cruising through the space between the stars, you can repair damage from particle impacts. Also, the ship splits into dozens of pieces separated by thousands of kilometers, enough spacing so that if part of the ship collides with a large mass at 90% of the speed of light, the rest of the ship survives.
Once at the destination star and decelerated to rest relative to the star, the ship finds a small asteroid or comet near the star. It docks with it and uses the asteroid/comet as raw materials to begin expanding infrastructure. The star provides an energy source. With exponential growth, each asteroid or comet consumed increases the infrastructure (aka a swarm of various types of robots) available, allowing bigger objects to be consumed. Eventually, there would be enough equipment built to start tearing down moons for raw materials, and eventually even planets.
Once all the mass in the star system is consumed and converted into more robots, processors, etc more ships are built and sent off like seeds to more stars to continue the process.
In principle, the entire galaxy would be nothing but dyson spheres within a million years or so.
The ultimate Fermi paradox is why has this not happened yet. We are nearing the technological capability to do this. I think we will have molecular manufacturing within 100 years. Once we find a way to copy the complexity of human brains to far faster solid state circuitry, we will create super-intelligent beings who would have the ability to solve all the engineering problems within a matter of years. If the Singularity happens, then after that event this kind of expansion would be expected to start right away. Worst case scenario, within 1000 years this should start happening.
Gravitational microlensing surveys have been looking for brown dwarfs and dim stars (sufficiently low luminosity they are not visible from Earth) in the galactic halo, but not enough were found to explain the mass difference (between luminous and non luminous galactic matter) to explain the observed galactic rotation curves. Planets around such low mass stars can also be seen (and have been seen, see the results by Microlensing Observations in Astrophyics [MOA] Project and associated collaborators - disclaimer I'm a former member). Depending on how small the planets are, they also could be detected (if you get very very lucky, due to the optical alignment required between observer, missing mass, and background luminous object). Given the constraints of the proportions of baryonic matter during the primordial nucleosynthesis (Big Bang/early universe) and the observed microlensing rate brown dwarfs are unlikely to account for the dark matter (AFAIK, I've been out of the game for a while). The baryonic constraints eliminated small rocks and gas clouds etc too. (I'm no expert on the nucleosynthesis calculations, however).
It would not be unusual for someone to come up with a theory that didn't take into account the known observations. For example, during the 1990's the early gravitational microlensing surveys 'rediscovered' the fact that our Galaxy is a 'barred spiral' - something the search teams were not aware of at the start of their studies (although astronomers, a different type of scientist, did know this). So it would not be unusual for someone to be missing key observations that invalidate this 'many planet theory'. Fortunately for the microlensing surveys their observations and results lead them to the correct conclusion (barred spiral galaxy), which instilled confidence in their methods and results. It doesn't take away from the fact that what was already known by astronomers was not at the time commonly known amongst the astrophysicists/particle physicists who designed the early microlensing surveys. It wouldn't surprise me if this was also the case in the paper /theory being discussed in this thread.
If human of Planet Earth can think of nomad planets being vehicles to cruise the universe, you think sentient aliens from other planets wouldn't think of he same thing?
Perhaps they already are doing that
As I see it, there are a couple of big problems with nomad planets. Available energy is hard to use. The environment would probably be very close to 4K (the temperature of the cosmic microwave background). I guess that there would probably be some sort of fusion, fission, or gravitational resources available for many of these places. But I doubt much energy will be available without serious technology.
Alternately, you might have life adapted to this environment with extremely slow metabolism (here, I include Earth nonlife examples such as electronics/integrated circuit systems and clockwork mechanisms). Such adaption has a price. The beam of a flashlight or the warmth of a human body even through an insulated suit might be lethal to them.
But over a long enough time, there's probably a nomad planet traveling close to you at a decent rate of speed and traveling in a direction you want to go.
According to NASA only 50% of astronauts who have spent more than 6 months in space have eye damage. That is still a significant problem, but not quite as severe as you make it out to be. Additionally, they report that 60% of those who spend more than 30 days in space have some health problems as a result. They are more interested in figuring out why the other 40% do not.
The truth is that all men having power ought to be mistrusted. James Madison