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There is talk, due to the analysis of the orbits of dwarf planets being discovered, that their maybe another major planet outside of the orbit of Neptune. What if it turned out to be a 50 Jupiter mass brown dwarf? And lets say that brown dwarf has a satellite orbiting it within its habitable zone. The dwarf radiates mostly infrared radiation, so it is this that is heating up its satellites. What would the difficulties be in sending humans to a brown dwarf satellite, lets say it was Earth sized, had oceans and continents, was tidally locked with the brown dwarf, and orbited in a near circular orbit within the habitable zone as defined by the infrared radiation. Do you think plant life might exist in such a place?
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Ignoring the fact that this is almost definitely not the case (if something so large were present, its gravitational effects would have been obvious even if it were 1 ly away), the hardest thing to do would be to get there. Neptune is 4.5 billion km from Earth, so if you blast off from LEO with a craft containing escape velocity and 10 km/s extra, you'll get there in more than 15 years just to get there. That's way longer than even a Mars mission. Given a 30 year round trip time, it doesn't make sense to make a mission anything but one-way, and given that it does take 15 years to send new equipment, backups, or spares, you've got to be extra confident that what you're sending will work and be sufficient.
In that situation life would almost definitely possible, but would probably take a slightly different form than life on Earth, insofar as it would have evolved to take advantage of infrared instead of visible light. It could otherwise be more or less identical.
-Josh
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There probably is a brown dwarf 1 light year away, something in between Jupiter and Proxima Centauri, the smaller the mass of the object, the closer it I likely to be to our Solar System. If the Brown Dwarf is only passing through, its effects might not be noticed for some time. Remember the Nemesis Theory for the extinction of the Dinosaurs?
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No, there is almost certainly no brown dwarf. WISE would have found it otherwise.
Neptune mass worlds, however, may be quite abundant, and are colonisable...
Use what is abundant and build to last
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There probably is a brown dwarf 1 light year away, something in between Jupiter and Proxima Centauri, the smaller the mass of the object, the closer it I likely to be to our Solar System. If the Brown Dwarf is only passing through, its effects might not be noticed for some time. Remember the Nemesis Theory for the extinction of the Dinosaurs?
Analysis of the periodicity of mass extinction events as well as the orbits of comets has disproved the "Nemesis" hypothesis fairly conclusively. It's true that we don't know quite what's out there, it is extremely unlikely that there's a brown dwarf.
Terraformer, it was my understanding that the results of WISE had not been fully analyzed yet?
-Josh
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When travel times with current technology are measured in years, it seems a bit silly to talk about sending manned missions to the Oort cloud. We would need some real breakthroughs in propulsion.
Back of the envelope for a really large (20,000+ ton) nuclear pulse propulsion ship: Isp 20,000 s and vehicle acceleration 2 gees "typical". Distance to target: assumed to be 10 billion km. Delta Vee one way from here to there: assumed to be 30 km/s. Carry enough nukes for 60 km/s two-way trip, as a single stage vehicle. I may be wrong, but I got a mass ratio of 1.358, for 23% nuke propulsion charges of the total departure mass. It accelerates in about 0.2 hr to 15 km/s, and takes around 21 years to get there, coasting at 15 km/s.
Clearly, even a nuke pulse propulsion ship like that would have to fly much, much faster to make such a voyage practical.
Go to 65% propellant, mass ratio 2.857. Total delta vee 206 km/s. 103 for the 1-way trip. coast velocity near 51.5 km/s. 1-way travel time now near 6 years.
Now make it a 1-way mission, so the coast velocity is 103 km/s. Still near 3 years.
Guys, we really need "warp drive" for these sorts of missions.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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When travel times with current technology are measured in years, it seems a bit silly to talk about sending manned missions to the Oort cloud. We would need some real breakthroughs in propulsion.
Back of the envelope for a really large (20,000+ ton) nuclear pulse propulsion ship: Isp 20,000 s and vehicle acceleration 2 gees "typical". Distance to target: assumed to be 10 billion km. Delta Vee one way from here to there: assumed to be 30 km/s. Carry enough nukes for 60 km/s two-way trip, as a single stage vehicle. I may be wrong, but I got a mass ratio of 1.358, for 23% nuke propulsion charges of the total departure mass. It accelerates in about 0.2 hr to 15 km/s, and takes around 21 years to get there, coasting at 15 km/s.
Clearly, even a nuke pulse propulsion ship like that would have to fly much, much faster to make such a voyage practical.
Go to 65% propellant, mass ratio 2.857. Total delta vee 206 km/s. 103 for the 1-way trip. coast velocity near 51.5 km/s. 1-way travel time now near 6 years.
Now make it a 1-way mission, so the coast velocity is 103 km/s. Still near 3 years.
Guys, we really need "warp drive" for these sorts of missions.
GW
There is even the nuclear salt water rocket by Zubrin: http://en.wikipedia.org/wiki/Nuclear_salt-water_rocket
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A cold brown dwarf 7.2 light years away. What are the chances of finding a brown dwarf closer?
NASA discovers the sun has an icy neighbor
NASA's Wide-field Infrared Survey Explorer (WISE) and Spitzer Space Telescope have found what appears to be a brown dwarf, or star-like object, that is as cold as the North Pole, just 7.2 light-years away from the sun.
The closest solar system to the sun is Alpha Centauri, about 4 light-years away.
"It is very exciting to discover a new neighbor of our solar system that is so close," Kevin Luhman, an astronomer at Pennsylvania State University's Center for Exoplanets and Habitable Worlds, said in a statement. "And given its extreme temperature, it should tell us a lot about the atmosphere of planets, which often have similarly cold temperatures."
Brown dwarfs begin as collapsing balls of gas, just like any other star, but they do not have enough mass to sustain nuclear fusion. This new brown dwarf — named WISE J085510.83-071442.5 — was found after WISE surveyed the entire sky at least twice using infrared light (NASA says that cooler objects stand out in infrared light because it capturestheir thermal glow). It is between -54 and 9 degrees Fahrenheit, which is much colder than the other brown dwarfs discovered by WISE and Spitzer, thought to be around room temperature.
"It is remarkable that even after many decades of studying the sky, we still do not have a complete inventory of the sun's nearest neighbors," Michael Werner, Spitzer's project scientist at the Jet Propulsion Lab, said in a statement. "This exciting new result demonstrates the power of exploring the universe using new tools, such as the infrared eyes of WISE and Spitzer." The animation below, courtesy of NASA/JPL-Caltech/Penn State, shows how the brown dwarf was spotted, thanks to its rapid motion across the sky. --Catherine Garcia
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As far as we know, we don't know its mass. Brown dwarfs are typically the size of Jupiter, but we don't know how many Jupiters worth of mass are packed into that Jovian volume, maybe it is just one! Jupiter radiates more energy than it receives as well. I'll bet this brown dwarf also has satellites.
Last edited by Tom Kalbfus (2014-04-28 05:17:33)
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Current sky surveys indicate that brown dwarfs are probably as numerous as lit stars. Except in our region of space, apparently, where they're only 1/6 as common - but given that we keep discovering more, I think they will turn out to be just as common here as well. In which case, there may well be one within 4.4ly, though it's very unlikely to be closer than 3ly. But, a roundtrip mission 3ly should be doable with beamed power and ram augmented interstellar rockets...
I'm looking somewhat further afield, though, at Luhman 16 - a binary system 6.6ly out. I don't think brown dwarfs are going to be targeted by hypothetical post singularity Von Neumann machines looking to build dyson spheres, see...
Use what is abundant and build to last
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Current sky surveys indicate that brown dwarfs are probably as numerous as lit stars. Except in our region of space, apparently, where they're only 1/6 as common - but given that we keep discovering more, I think they will turn out to be just as common here as well. In which case, there may well be one within 4.4ly, though it's very unlikely to be closer than 3ly. But, a roundtrip mission 3ly should be doable with beamed power and ram augmented interstellar rockets...
I'm looking somewhat further afield, though, at Luhman 16 - a binary system 6.6ly out. I don't think brown dwarfs are going to be targeted by hypothetical post singularity Von Neumann machines looking to build dyson spheres, see...
Brown Dwarfs would make great Dyson Spheres, but only as a gravitational object in the center, it would still need an exterior source of illumination and people would live on the outside of it. Lets say you had a 20 Jupiter mass brown dwarf, how big would the 1-G Dyson Sphere be?
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I don't think you're quite understanding the purpose of a dyson sphere... The idea is energy, not gravity. But, should you want to build a 1g surface around a brown dwarf with a mass 20 times larger than Jupiter, it would have a radius of about 78 times that of Earth, just about 500,000 km.
-Josh
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If you want to live on a Dyson sphere, having a hot star in the center would be a problem because
A) you can't live on the inside of the sphere, gravity would pull towards the star,
B) the star's gravity would be slight at the star's habitable zone, so it would do little good for holding things onto the outside
C) At he 1-G radius of most stars the radiance is too great, and you have the problem of dissipating the heat from the star.
But a brown dwarf such as the one that was discovered would be cool, and in addition it probably has satellites out of which you could build.
You could put a 1-G sphere around a brown dwarf and surround it with a slightly larger Dyson Sphere, both build out of materials orbiting the brown dwarf. Presumably some of this material would make suitable fusion fuel, and building a fusion reactor or reactors on the scale of the planets should not be a big problem if you can build on this scale. With the power generated you can illuminate the inner sphere for day and night, it would have about 6000 times the surface area of the Earth if it massed 20 Jupiters.
Last edited by Tom Kalbfus (2014-04-28 15:35:24)
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A Dyson sphere or a supramundane habitat is very farr from our actual capability. But we can imagine a planet in the brown dwarf habitable zone, tidally locked, heated by infrared radiation and by tidal vulcan activity, with an almost black alien vegatation that use infrared radiation for photosynthesis.
We can use a laser driven photonic sail for acceleration and a nuclear pulse for deceleration in the outward voyage and nuclear pulse for acceleration and a laser photonic sail for deceleration for the inward voyage.
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Plus, Dyson spheres require such advanced technology that we'll certainly be beyond physical bodies by then.
This is even disregarding the fact that there won't be any gravity since the Dyson sphere will be orbiting.
-Josh
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Plus, Dyson spheres require such advanced technology that we'll certainly be beyond physical bodies by then.
This is even disregarding the fact that there won't be any gravity since the Dyson sphere will be orbiting.
Some of us will be beyond physical bodies, but not necessarily all. Compare this to evolution, despite the fact that we evolved, microbes still exist, we haven't made them obsolete, they still continue to thrive in the world we inhabit.
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Some more detail on the brown Dwarf here:
http://news.yahoo.com/nasa-discovers-co … 16839.html
It appears to be from 3 to 10 Jupiter masses, a smaller Dyson Sphere then. It maybe a rogue gas giant. From the other gas giants we know about this one may have icy moons orbiting it. We could build a colony on one of those, and its conceivable that we could build a spaceship that could reach it in 100 years. Does it really make a difference whether we colonize a system with a star at its center or a rogue gas giant? if we can build fusion reactors, and we'll need at least those to get there, then perhaps not. Another source of energy may be tidal heating. If there is a Satellite like Io, then we might somehow tap those volcanos for energy.
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Compare the needs of a physical human to the needs of a much more powerful conscious being running on a computer. Why will physical humans have rights to excessive and wasteful materials? Upload, or the cost of living will become prohibitively expensive.
-Josh
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Here's a comparison for you: let's say an Amish person lived in Manhattan. Because they don't believe in using technology, they would need several acres of farmland to survive. Is there any chance a person would be allowed to turn an area the size of the Financial district into farmland, with its billions worth of property values? It's not even remotely feasible.
-Josh
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Is there a shortage of materials or energy in this Universe? Everywhere we look, we see wasted energy, stars shining out into nothingness.
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If we have a reason to build a dyson sphere, yes, that implies that we do have a need for large amounts of energy. Because we'll be making a dyson sphere, we will also find ourselves at a shortage for mass.
-Josh
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A Dyson Sphere around a brown dwarf isn't 1 AU in radius, therefore much less mass is required. There will probably be satellites orbiting the brown dwarf which could be used for construction material. if the brown dwarf is 3 Jupiter masses, a satellite which is the same proportion to the brown dwarf's mass as Jupiter is to the Sun, would be about 1 Earth mass. So you'd have about 1 Earth mass worth of material to make 2 Dyson shells out of. Do you think that is enough material?
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Wut? You build a dyson sphere (cloud) to collect solar energy, of which there is very little around a brown dwarf. Best places for those are red dwarfs, given that they are the most efficient stars.
Josh, what would give urbanites the right to size existing Amish farmland, because they can "make better use of it"? This isn't a hypothetical question - we already had such a scenario with the invention of farming (and to an extant, the settling of North America, but since that was a post apocalyptic land at the time, there actually *was* unused land).
It's a potential scenario for our first interstellar war. But since hypothetical (and unlikely) uploaded people would be running on much faster hardware, they might find that the 1000s of years of subjective time needed to reach even the nearest star is too much, and settle for disassembling the inner planets to make a Matrioshka brain. An answer to the Fermi paradox? I've seen it suggested, but I think it would tend to drive interstellar colonisation, as people flee the abomination that has destroyed their homeworlds to feed its hunger.
Use what is abundant and build to last
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There are 100 billion stars in the Galaxy, more than 10 stars for every living person on Earth, and they are all radiating into space, wasting their energy. Seems that is AIs are following the maximum efficiency paradigm, the would fill the Solar System up to maximum occupancy first before traveling to the stars.
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Terraformer, there are actually a variety of ways. These include zoning laws, property taxes (if you're paying a 1% property tax on the value of one hectare of land on Manhattan, farming just isn't going to cut it), or, most comparable to what we're discussing, you could go build a new city somewhere and not include any farmland inside the city limits.
-Josh
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