With the discovery of five planets orbiting the star Tau Ceti, does this mean all the sf literature on that system is now obsolete?
My take is that Asimov, Clarke, Niven, and others will eventually pass into the realm of Jules Verne and Edgar Rice Burroughs. These guys were skilled authors with great imaginations. Memorable characters, too. But eventually the factual truth about the universe–in this case other planetary systems–will come out. And we’ll be left to entertain ourselves by the quality of the writing. From the Universe Today site:
(T)his new discovery is the closest single sun-like star that we know of to host of an entire system of planets. The five planets are estimated to have masses between two and six times the mass of the Earth, making it the lowest-mass planetary system yet detected. The planet in the habitable zone of the star has a mass around five times that of Earth, making it the smallest planet found to be orbiting in the habitable zone of any Sun-like star.
I want to get to that “habitable zone” in a bit. But first, a thought that Tau Ceti may be more appealing than twentieth century guesswork in the books:
- As you can see above, when compared to the sun (left) Tau Ceti is bit smaller, less spotty, and more orange than our home star. If God decided to pull a cosmic switcheroo and give our solar system Tau Ceti one morning, we’d be deep in an ice age within a few years. Earthlike planets will need to huddle closer to that star.
- Tau Ceti is thought to be older than the sun. Generally speaking, astronomers think lower metal content in a star implies a formation farther back in time, before as many supernovae blasted as much iron, nickel, gold, etc. into the cosmos. One presumes that Tau Ceti’s planets will have less iron and rock, and more lighter elements and compounds: carbon, nitrogen, water, methane, ammonia, etc..
- Astronomers have detected about ten times as much “debris” around Tau Ceti. Amateurs are surprised to find out that it is easier for Earthlings to detect dust belts, gas clouds, and debris than it is to find planets. Ten times more asteroids, comets, and space dust swirl in Tau Ceti orbit. Given these new planets are so close in (inside the orbit of Mars in our system) I wonder if all the debris isn’t orbiting a bit farther out. I wonder if astronomers have fine tuned the location of all that junk.
- Astronomers have ruled out a Jupiter-sized planet, unless it’s way, way out from the other five. Jupiter is thought to protect Earth from too many comets and asteroids because it has swallowed up so many over the past billions of years. But on the other hand, without a Jupiter, Tau Ceti’s inner planets may be relatively safe from the occasional asteroid perturbed into an inner system visit.
Here’s why I’m a skeptic on habitable zones. Planets and moons can be warmed by things other than sunlight. Radioactive decay warms the Earth’s interior to the temperature of the sun. Tides of the moons of Jupiter keep rock molten and subsurface oceans liquid.
There is another reason that habitable planets are probably never going to be relevant for human travel in space, if we ever make it to the stars. It will take a ship thousands of years to travel the interstellar gulf. That ship will probably be the size of an asteroid or small moon, and will carry all the creature comforts of home. Even if Tau Ceti travellers were to find a nice planet on arrival, a large portion of the human occupants might prefer to stay on board ship. Why disembark to a planet with lots of unknowns?