We Explored Pluto, Now Let’s Explore The Nearest Star!

On July 14th, 2015, the New Horizons space probe made history when it became the first spacecraft to conduct a flyby of the dwarf planet of Pluto. Since that time, it has been making its way through the Kuiper Belt, on its way to joining Voyager 1 and 2 in interstellar space. With this milestone reached, many are wondering where we should send our spacecraft next.

Naturally, there are those who recommend we set our sights on our nearest star – particularly proponents of interstellar travel and exoplanet hunters. In addition to being Earth’s immediate neighbor, there is the possibility of one or more exoplanets in this system. Confirming the existence of exoplanets would be one of the main reasons to go. But more than that, it would be a major accomplishment!

Located 4.3 light years from Earth, the Alpha Centauri system consists of three stars – Alpha Centauri A, B, and C (aka. Proxima Centauri). For many years now, exoplanet hunters have been divided on the issue of whether or not it has a system of planets. This began in February of 2008, when a team of European observers working at the European Southern Observatory’s La Silla facility in Chile began searching for a possible exoplanet in orbit of Alpha Centauri B – which was designated Alpha Centauri Bb.

Alpha Centauri A and B (shown to scale), and their respective habitable zones (not to scale). Credit: PHL/UPR Arecibo

Using the Doppler spectroscopy method, they recorded measurements of Alpha Centauri B’s radial velocity and color spectrum over a four-year period. They then applied statistical filters to remove known sources of variance to be sure that what they were detecting was indeed a planet, and not background noise.

In October of 2012, in an article submitted to the scientific journal Nature, they officially announced the existence of Alpha Centauri Bb. According to the team, the planet was similar in mass to Earth and orbited Alpha Centauri B within its habitable zone (aka. “Goldilocks zone”). This made it the closest Earth-like exoplanet discovered to date.

However, three years after the announcement, in October 2015, researchers from the University of Oxford published a paper entitled “Ghost in the Time Series” which indicated that there were flaws in the original analysis. According to the paper, the signal that was observed by the ESO team naturally arose from the “window function” of the original data – aka. it was a ghost signal.

However, in March of 2015, the same scientific team published a paper that proposed the existence of other alien world orbiting Alpha Centauri B. Using data from the Hubble Space Telescope, they discovered evidence of a possible transit in front of the B star. If confirmed, this planet would be called Alpha Centauri Bc, and is apparently located too close to its parent star to support life.

Artist’s concept of Dawn above Ceres. Since its arrival, the spacecraft turned around to point the blue glow of its ion engine in the opposite direction. Image credit: NASA/JPL

Hence why scientists like Dr. Debra Fischer – a professor of astronomy at Yale University, and a member of the Planetary Society who has discovered hundreds of exoplanets – are advocating for a mission to the Alpha Centauri system. As she told Universe Today via email:

“The Kepler mission demonstrated that almost every star has planets and we have found planets orbiting stars that are in binary systems not too different from Alpha Centauri. It’s a good bet that there are planets there that we just have not been able to find yet, given current precision… It will likely take a spacecraft in a low Earth orbit with sufficient measurement precision to detect small rocky planets in the system.  Once we find them, then we will be highly motivated to send robotic spacecraft to look for life.”

Naturally, sending a spaceship to the nearest star system represents a major challenge. As we explained in a recent article – How Long Would It Take To Get To The Nearest Star? – even with our most advanced technology, it still would take thousands of years to reach Alpha Centauri – between 72,000 and 81,000 to be exact. Considering that 3000 to 4000 generations would pass between launch and arrival, that hardly seems worth it.

Even reckoning for the fastest speed ever achieved by a spacecraft – 240,000 km/hr (150,000 miles/hr), which was accomplished by the Helios 2 probe in the late 1970s – the trip would still take a whopping 19,000 years. In order to make this trip is a single lifetime, during which the spacecraft could reach Alpha Centauri and radio back its findings, something new and experimental would need to be developed.

Weighing in at 60,000 tons when fully fuelled, Daedalus would dwarf even the Saturn V rocket. Credit: Adrian Mann

For decades now, ideas ranging from nuclear-thermal propulsion and solar sails have been considered, and some of these proposals are within the realm of possibility. At the more radical end of things, concepts such as nuclear-pulse spacecraft (i.e. Project Orion), fusion containment (i.e. Project Daedalus, shown above) and fusion ramjets have been suggested – ideas that, while possible, would be incredibly expensive to build.

And whereas some of these concepts are feasible in the near-term (and using current technology) others are still very much in the theoretical phase, like the Alcubierre “Warp” Drive. Others still, such as the Radio Frequency Cavity Thruster (aka. the Cannae, or EM Drive), have been tested, but not to satisfaction of many in the scientific community.

But as Fischer explains, these sorts of challenges have not stopped us before. And there are several options on the table, the development of which could have beneficial applications here on Earth.

“When you study the energy requirements, it is a daunting goal,” she said. “But needing to beat the odds has never stopped us before. We would need to figure out how to accelerate a swarm of networked robotic spacecraft so that they can reach this star system in something like 40 years. “We will have to build receivers with the sensitivity to pick up messages from the Alpha Cen bots. The pathway to solving those questions will have technology spinoffs as impactful as cell phones, lap tops, or GPS.”

The distance between our Sun and Alpha Centauri (and all that lies in between) using a logarithmic scale. Credit: NASA

Regardless of the destination, any bold new step in the field of space exploration will have to involve serious planning and careful consideration. Now that we have effectively explored the Solar System, reaching beyond will be a major challenge. But as the history of space exploration teaches us, accepting a major challenge is a great way to bring out the very best in us.

Even when the goal seems insurmountable at first glance, working towards it can lead to many great and interesting breakthroughs, some of which have far-reaching benefits. As Fischer added, setting Alpha Centauri as our next goal is every bit as ambitious as our ancestors decision to go to the Moon, and offers similar rewards.

“The exploration of Alpha Centauri is a grand vision for humanity,” she said. “In the 1960’s, we sent Apollo missions to explore the moon, and humanity just took another big leap with the New Horizons mission, traveling to the outermost reaches of our solar system. Sending a mission to Alpha Centauri could be the next big stepping stone.”

Here’s hoping some of our more radical ideas start bearing fruit in the coming years. Otherwise, any missions to Alpha Centauri will be very “slow boat” in nature, and I for one would like to live to see what’s really there!

Matt Williams

Matt Williams is a space journalist and science communicator for Universe Today and Interesting Engineering. He's also a science fiction author, podcaster (Stories from Space), and Taekwon-Do instructor who lives on Vancouver Island with his wife and family.

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