[BRIEF NOTE] Why Epsilon Indi Is So Cool
Sep. 5th, 2004 11:20 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
rfmcdonaldEarly 20th century astronomers, of course, famously believed that Venus and Mars were relatively Earth-like and human-habitable worlds, though Venus tended towards swamp and Mars towards desert. Indeed, they may have been that way a billion or so years after Sol system's formation, before the Sun's warning turned Venus into a hellish desert and Mars' low gravity allowed its primordial atmosphere to escape. That's unfortunate for us, I suppose.
Science-fiction writers have always liked the ideas of planetary systems with multiple inhabitable planets. Kurd Lasswitz, author of The Two Planets, is one of the earliest modern writers who imagined a planetary system where humans--or, at least, interfertile humanoids--could be found on two separate worlds. A truly biplanetary--or multiplanetary--human civilization spread over multiple inhabitable globes allows the civilization a degree of scope, a certain amount of freedom, that a civilization confined to a single globe and a collection of cramped space settlements could not. That's where much of the romance behind the idea of terraforming Mars, expressed most recently in Kim Stankley's Robinson's Mars series (Red Mars, Green Mars, Blue Mars, The Martians), comes from. The idea that humanity can remedy nature's mistake and create a second living world just next door, a place where we can enjoy new horizons without the decades of time needed for interstellar travel, is fun.
Three worlds (Venus, Earth, Mars) might once have supported Earth-like conditions in our planetary system; only one does now. The book Rare Earth (referenced with my review of Lasswitz above) suggests that it may be difficult to sustain Earth-like conditions, or even to generate them in the first place. Judging by the limited evidence we have in our own planetary system, it seems like we might need two planetary systems to have a better chance at generate two habitable worlds. Fortunately for our purposes, planetary systems with more than one star are quite common. Sol is the only star in its planetary system, the unconvincing Nemesis hypothesis aside.
The nearest multiple-star planetary system is Alpha Centauri. Also the nearest planetary system to our own, just a billion years older, and located just far enough to let planets form in viable orbits, two of Alpha Centauri's three stars happen to be reasonably Sol-like: Alpha Centauri A falls in the same spectral classification as our own Sol and is somewhat bright, while Alpha Centauri B is a bright orange dwarf star. Science-fiction settings frequently place at least one habitable world in the Alpha Centauri system--the 2300AD/2320AD RPG places humanity's oldest colony world, Tirane, in orbit of Alpha Centauri A. The problem with Alpha Centauri, though, is that it's a clichéd location. Let's be serious, now: What popular science-fiction setting hasn't had largish colonies, if not a second human homeworld, in the Alpha Centauri system? It's just not unexpected enough; it's not sophisticated enough.
Within twenty light-years of Sol, there are other multiple-star planetary systems with Sol-like stars: 61 Cygni, 70 Ophiuchi, Eta Cassiopeiae. 61 Cygni A and B, though, not only are fairly dim stars, but appear--based on the orbit of 61 Cygni C, a superjovian planet--to have eccentric planetary orbits which would swing planets in and out of habitable zones. The Ophiuchi and Cassiopeiae binaries, in the meantime, might orbit too closely to allow planets to form at all, or to orbit their primaries in stable orbits. And thus, it seemed things had to be left here. Multiple Earth-like worlds in a single planetary system close to us would, it seemed, have to take advantage of extraordinary runs of luck.
This is until Epsilon Indi. Epsilon Indi is an orange dwarf some 11.8 light years away from us, roughly the same distance and in the same direction as the more famous stars of Tau Ceti and Epsilon Eridani. Epsilon Indi is also a young planetary system, barely more than a billion (thousand million) years old, thus frequently excluded from SETI searches which concentrated on planetary systems presumably old enough to develop native sophont species. Epsilon Indi was overlooked, that is, until last year, when scientists discovered that a large brown dwarf orbited the star. Brown dwarves, incidentally, are large stellar objects which don't have enough mass to trigger self-sustaining nuclear fusion like more massive stars, usually estimated to mass between 10 and 70 Jupiters, instead generating energy through slow gravitational contraction. As the scientists continued their researches, it turned out that what they thought was a single brown dwarf was actually two brown dwarfs, orbiting each other as they wind their way around the bright star of Epsilon Indi A.
This is cool to start with. I mean, binary brown dwarves? For our purposes, though, it's important that these brown dwarves are both relatively massive and relatively young, hence relatively Last August,![[livejournal.com profile]](https://www.dreamwidth.org/img/external/lj-userinfo.gif)
evildrganymede posted an article on the Journal of the Traveller's Aid Society, bringing the latest scientific knowledge of brown dwarfs out for people to use. Plugging in the figures for the Epsilon Indi brown dwarves, I found to my interest that habitable zones exist around both brown dwarves.
Granted that the Epsilon Indi system is young, it's possible that evolution has proceeded more quickly, or that Earth-derived biospheres could be planted (or, perhaps, could have been planted) on the multiple worlds in that planetary system. It's a fun idea, isn't it, to imagine different worlds orbiting two glowing embers of quasi-stars along with a brighter orange dwarf?
I want to write something set there. I really do.
Science-fiction writers have always liked the ideas of planetary systems with multiple inhabitable planets. Kurd Lasswitz, author of The Two Planets, is one of the earliest modern writers who imagined a planetary system where humans--or, at least, interfertile humanoids--could be found on two separate worlds. A truly biplanetary--or multiplanetary--human civilization spread over multiple inhabitable globes allows the civilization a degree of scope, a certain amount of freedom, that a civilization confined to a single globe and a collection of cramped space settlements could not. That's where much of the romance behind the idea of terraforming Mars, expressed most recently in Kim Stankley's Robinson's Mars series (Red Mars, Green Mars, Blue Mars, The Martians), comes from. The idea that humanity can remedy nature's mistake and create a second living world just next door, a place where we can enjoy new horizons without the decades of time needed for interstellar travel, is fun.
Three worlds (Venus, Earth, Mars) might once have supported Earth-like conditions in our planetary system; only one does now. The book Rare Earth (referenced with my review of Lasswitz above) suggests that it may be difficult to sustain Earth-like conditions, or even to generate them in the first place. Judging by the limited evidence we have in our own planetary system, it seems like we might need two planetary systems to have a better chance at generate two habitable worlds. Fortunately for our purposes, planetary systems with more than one star are quite common. Sol is the only star in its planetary system, the unconvincing Nemesis hypothesis aside.
The nearest multiple-star planetary system is Alpha Centauri. Also the nearest planetary system to our own, just a billion years older, and located just far enough to let planets form in viable orbits, two of Alpha Centauri's three stars happen to be reasonably Sol-like: Alpha Centauri A falls in the same spectral classification as our own Sol and is somewhat bright, while Alpha Centauri B is a bright orange dwarf star. Science-fiction settings frequently place at least one habitable world in the Alpha Centauri system--the 2300AD/2320AD RPG places humanity's oldest colony world, Tirane, in orbit of Alpha Centauri A. The problem with Alpha Centauri, though, is that it's a clichéd location. Let's be serious, now: What popular science-fiction setting hasn't had largish colonies, if not a second human homeworld, in the Alpha Centauri system? It's just not unexpected enough; it's not sophisticated enough.
Within twenty light-years of Sol, there are other multiple-star planetary systems with Sol-like stars: 61 Cygni, 70 Ophiuchi, Eta Cassiopeiae. 61 Cygni A and B, though, not only are fairly dim stars, but appear--based on the orbit of 61 Cygni C, a superjovian planet--to have eccentric planetary orbits which would swing planets in and out of habitable zones. The Ophiuchi and Cassiopeiae binaries, in the meantime, might orbit too closely to allow planets to form at all, or to orbit their primaries in stable orbits. And thus, it seemed things had to be left here. Multiple Earth-like worlds in a single planetary system close to us would, it seemed, have to take advantage of extraordinary runs of luck.
This is until Epsilon Indi. Epsilon Indi is an orange dwarf some 11.8 light years away from us, roughly the same distance and in the same direction as the more famous stars of Tau Ceti and Epsilon Eridani. Epsilon Indi is also a young planetary system, barely more than a billion (thousand million) years old, thus frequently excluded from SETI searches which concentrated on planetary systems presumably old enough to develop native sophont species. Epsilon Indi was overlooked, that is, until last year, when scientists discovered that a large brown dwarf orbited the star. Brown dwarves, incidentally, are large stellar objects which don't have enough mass to trigger self-sustaining nuclear fusion like more massive stars, usually estimated to mass between 10 and 70 Jupiters, instead generating energy through slow gravitational contraction. As the scientists continued their researches, it turned out that what they thought was a single brown dwarf was actually two brown dwarfs, orbiting each other as they wind their way around the bright star of Epsilon Indi A.
This is cool to start with. I mean, binary brown dwarves? For our purposes, though, it's important that these brown dwarves are both relatively massive and relatively young, hence relatively Last August,
evildrganymede posted an article on the Journal of the Traveller's Aid Society, bringing the latest scientific knowledge of brown dwarfs out for people to use. Plugging in the figures for the Epsilon Indi brown dwarves, I found to my interest that habitable zones exist around both brown dwarves.Granted that the Epsilon Indi system is young, it's possible that evolution has proceeded more quickly, or that Earth-derived biospheres could be planted (or, perhaps, could have been planted) on the multiple worlds in that planetary system. It's a fun idea, isn't it, to imagine different worlds orbiting two glowing embers of quasi-stars along with a brighter orange dwarf?
I want to write something set there. I really do.
