Alpha Centauri A and B
Proxima is inside the red circle
Image By Skatebiker at English Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=46833562
Copyright © 2016
by Ralph F. Couey
Except cited portions
On September15, 1965, the CBS television network debuted a new science fiction show entitled “Lost in Space.” The Irwin Allen production followed the adventures of the Robinson family who were being sent on an interstellar mission to find a new place for an over-populated earth to call home. The show was known far more for its campy style than anything else. The main character became, not the Robinson’s, but the evil conniving Dr. Zachary Smith, who had snuck aboard as a foreign agent to sabotage the mission, but managed to get stuck there when the ship took off. He was certainly the most buffoonish foreign agent ever, in addition to being a sniveling coward of the first order, and the episodes mainly revolved around Smith doing foolish things to get the Robinson’s in trouble. It was not intellectual by any stretch, but managed to stay on the air for three seasons before being canceled, according to statements by cast and crew, due to declining ratings and increasing costs.
So what, you may ask. Well, the destination for the Robinsons and their saucer-shaped Jupiter 2 spacecraft was Alpha Centauri, long known to be the closest star to our own solar system, about 4.2 light years away. According to the plot, there was a planet there that could support human life and it was the Robinson’s mission to survey the planet and report back.
As it has turned out, Irwin Allen seems to have been a prophet.
Today, we know Alpha Centauri is not just a single star, but a trinary system, consisting of two main stars, Alpha Centauri A and B, and a small and faint red dwarf known as Proxima Centauri. The two larger stars orbit a common center every 80 or so years at a distance from each other ranging from roughly the same distance as our sun to Pluto at apogee to a perigee about the same distance as our sun is from Saturn. Proxima lies further out, about 500 times the distance between our sun and the planet Neptune. While A and B are 110% and 90% of our sun’s mass, making them roughly equal to ours, Proxima is far smaller, only about 12% of our sun’s mass. In August 2016, the European Southern Observatory announced that an earth-sized exoplanet, dubbed Proxima B, had been discovered orbiting the cool, red star at about 20 percent of the distance of earth from our sun. The planet orbits the star every once every 11 earth days, so it has a year of less than two earth weeks. With the reduced output characteristic of red dwarf stars, that places Proxima B within the so-called “Goldilocks Zone,” close enough to have liquid water, yet far enough out that the water would not boil away. Little is known about this planet. An established astronomical procedure estimates that the planet’s mass is no less than one –and-a-quarter earths with an equilibrium temperature of -38 degrees F. A little chilly for my tastes. Scientists think that the planet is tidally locked, meaning that one side always faces its sun, while the other is in perpetual shadow, like Mercury. But there is a narrow band along the terminator between day and night that might provide a potential habitable environment. But if the planet has an atmosphere, a vehicle for transferring heat to the cold side, then temperatures might just be adequate for humans to live.
Of course some people are demanding that we travel there immediately, unaware that the distance involved, even with the fastest craft humans have ever built, means a transit time of 17,000 years. But there are initiatives out there now that could reduce that travel time.
Breakthrough Starshot is a concept utilizing light sail spacecraft. According to the designers, the system consists of about a thousand small craft with sails that would catch the emissions of several earth-based 100 gigawatt lasers that would act on the sails in the same way the wind acts on the sails of a sea-going ship. They estimate that the mothership attached to the individual modules could reach as much as 20% of the speed of light, making for a roughly 25-year journey. This project faces monumental technical challenges, but they insist they could have a craft underway in about 20 years.
Another possibility is an engine powered by nuclear fusion. This involves compressing plasma bubbles inside a chamber until the bubbles reach a fusion state, then squirting the by-product out the back end. Simulations suggest that such a system could get a spacecraft to the planet Mars in 80 to 90 days, rather than the current 500. It isn’t known whether such a system could be viable for interstellar journeys. At least no astronaut would get “Watneyed” on Mars.
Another idea involves nuclear fission, splitting atoms to create large amounts of heat to heat a lightweight propellant, like liquid hydrogen, and using that for thrust. This system could get a spacecraft to Mars in about 90 days. Again, there are significant technological and political hurdles to be surmounted.
A third possibility involves something called VASIMR, or “Variable specific Impulse Magnetoplasma Rocket.” VASIMR uses electromagnetic radiation to heat up and ionize gasses, like argon, xenon, or hydrogen and shooting that through a magnetic nozzle. This may be the closest thing to the impulse engines on the fictional Starship Enterprise. It’s slower than the other two, taking a year for a round trip, including time on the surface. The interesting facet to this is by using hydrogen as a propellant, the fuel storage tanks could serve as a radiation shield for the crew, once they venture beyond the protective umbrella of earth’s magnetic fields.
The ultimate system would involve anti-matter – specifically anti-protons. This really is Star Trek stuff, and as you might expect is decades, perhaps centuries away from realization.
The best part of this whole story is that the reaction to the news about the new planet shows that we humans haven’t lost our appetite for exploration. The last time a human being left earth orbit was the Apollo 17 mission in December of 1972, nearly 44 years ago, and that’s too long.
There are loads of problems to be solved, not the least of which is how to keep a crew from beating each other’s brains out on a long-duration mission. Outside of our planetary cocoon is a universe filled with all matter of hazards from rocks to radiation. It would be easy to just assume that it’s too dangerous out there for us. But we have chosen to solve the dangers and find ways to get such missions done. The first step is Mars, of course, and perhaps a manned exploration of the planet-sized moons of Jupiter and Saturn.
We’re not yet ready for a trip to another star, but as the decades and centuries roll past, eventually we could undertake such a mission. None of us will be around to see it, but space is patient. After all, Proxima B isn’t going anywhere anytime soon.