Is Alpha Centauri the right place to search for life elsewhere?

April 13, 2016 by Jonti Horner, University Of Southern Queensland, The Conversation
Alpha Centauri is actually the outer star (bottom right) of The Pointers, which point to the Southern Cross. Credit: Y. Beletsky (LCO)/ESO, CC BY

It sounds like science fiction. From the people who brought you the project Breakthrough Listen to search for extraterrestrial life, comes a new research program that's looking at sending a tiny spacecraft to the nearest stars.

The US$100 million plan is to push these probes out at speeds up to a fifth of the speed of light. To do this would require huge technological innovation, but it's certainly not beyond the bounds of possibility.

But if the project is to bear fruit, where should these minute spacecraft be sent? The first suggested target is the Alpha Centauri system, the closest stars to the solar system.

The first stop on an interstellar journey

Alpha Centauri appears a single star when seen with the unaided eye, and is the third brightest star in the night sky. But when observed through binoculars or a telescope, you can see the star is double – a binary star system.

The two bright components, Alpha Centauri A and B, are similar to our sun. One (A) is a bit brighter and bigger than our star and the other (B) a little fainter and smaller.

They move together in lockstep, orbiting their common centre of mass roughly every 80 years. As they do, they follow an elliptical path, with their closest approach (periapse) roughly 11 times further than the Earth is from the sun.

Alpha Centauri (the left-hand bright star), and Proxima Centauri (circled) are the closest stars to the sun. Beta Centauri (right-hand bright star) is almost a hundred times farther away. Credit: Skatebiker

And the two are not alone; they are accompanied by Proxima Centauri. Proxima is a dim , about an eighth the mass of the sun.

It currently lies a little closer to the Solar System than the other two, and so holds the distinction of being the closest star to the sun. Despite this, it is so dim that it is far too faint to see with the unaided eye.

Sunlike stars, but where are the planets?

As our nearest stars, the Alpha Centauri system has been an obvious target for the search for exoplanets. Dedicated search programs, such as the Mt John Alpha Centauri Project, look at the stars every single clear night, trying to uncover even the slightest hints that they might host planets.

The relative sizes and colours of the stars in the Alpha Centauri system and the sun. Credit: David Benbennick

Other programs on the world's largest telescopes observe less frequently, but with exquisite precision.

The result? Well, a few years back, the discovery of a planet around Alpha Centauri B was announced to much fanfare.

Had that planet been real, spotting it would have been groundbreaking. A tiny, broiled world, skirting the top of the star's atmosphere.

Sadly, though, as more observations have come in, the planet's existence has fallen into doubt. An extensive reanalysis has effectively added it to the pile of planets that never were.

So why go to Alpha Centauri?

Given that Alpha Centauri is currently viewed as a planet-free zone, why would we want to go there?

Probably the first and foremost reason is that it is nearby, closer than any other star. If the new spacecraft were to achieve the proposed fifth of the speed of light, it would only take 21 years or so to get there (depending on the time taken to accelerate). That is far shorter than the to any other known star.

Sending our first probes out to Alpha Centauri would mean we get our first closeup look at another star, far sooner than for any other known star. We'd also get a two-for-one peek, whizzing past Alpha Cen A and B up-close and personal.

The relative locations of some famous stars, relative to the sun. Credit: Andrew Z Colvin

We'd even get a wealth of data on Proxima Centauri, thrown in for good measure. We couldn't get all that close, though, since these spacecraft are going to be more like bullets than racing cars, fired outward from Earth.

And if there are planets around these stars, then we'd see them. In fact, if there are planets there, they'd likely be found before our tiny explorers reach the area (given the rate at which our techniques and telescopes are improving).

So we'd be able to let the spacecraft know, and plan its observations to take advantage.

Artist’s impression of Epsilon Eridani b, with the system’s asteroid belt visible in the background. Credit: NASA, ESA, G. Bacon
Looking further afield

Let's say the mission to Alpha Centauri is a success. Where should we go next?

One exciting target lies just a little further away than the stars in our table (above) and that's Epsilon Eridani. At just 10.5 light years distant (a travel time of a meagre 55 years for our tiny explorers), it is still one of our nearest neighbours.

Where Alpha Centauri is a multiple star system, with its sun-like stars so close as to render the formation of truly Earth-like planets challenging, if not impossible, Epsilon Eridani is a solitary wanderer, just like the sun.

A little smaller and dimmer than our star, it is known to have two disks of debris orbiting around it. Again, this is just like our sun. The inner disk looks a bit like our asteroid belt, around the same distance, around the same size.

Observations have revealed the presence of at least one massive planet in the system, moving on an orbit just outside the inner asteroid belt. Just like Jupiter in our solar system. There may well be others, lurking and awaiting discovery.

If we want to explore a system that might just be uncannily like our own, then Epsilon Eridani is probably the place we should look. But with a travel time of more than 50 years with the proposed technology, it makes sense to shoot for the closest first.

All aboard for Alpha Centauri!

Explore further: Stephen Hawking joins futuristic bid to explore outer space (Update)

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1.3 / 5 (12) Apr 13, 2016
This is insane. Send a message: "Vicious monkey are trying to get out of their star system".
Many points, just some listed: 1) If you look at constant wars and uprisings, and cruel dictatorships, drug cartels, oil companies, slave trade, human trafficking and just individual psychopaths - what you think any more enlightened alien, or an alien just like us on a higher technology level will think (if they exist, that is)? "Stop the vermin before they get here" comes to mind.
2) Granted, we will not change our nature. Why not wait until we have a real star travel technology? Why send micro-toys?
3) Just based on the top 2 points, the idea is so kindergarten infantile. I know, there will be responses - "we are so curious we just have to do it" - there are plenty of constructive scientific ways to be curious, if you have a brain; if you don't have a brain - just climb Everest, why don't you? Or "we feel so lonely" - well, get yourself a dog.
Apr 13, 2016
This comment has been removed by a moderator.
1.4 / 5 (9) Apr 13, 2016
Some do not understand. They HAVEN'T Heard What Hawking said in the Q&A session directly from his Brain to the Computer to the gathered Scientists.
He talked of the necessity for avoiding of putting ALL Eggs in a single Fragile Basket. Billions of Comets are CONSTANTLY Flying Around in the Universe. 1 MAY HIT our Earth Any Time. Previous Hit DECIMATED All Humongous Dinosaurs. They were turned into pulp. Smaller animals that fell into Sea Coasts Swam back to their safety!
The Day we Cannot Dodge such Flying Natural Missiles Anymore, we should be READY to RELOCATE to a safer Planet (Trillions out there) in a Jiffy! WE COULD SEE PLANETS OUTSIDE Our Solar System ONLY IN THE 1990's
So, Gathering of Knowledge SHOULD continue CONSTANTLY!
5 / 5 (2) Apr 13, 2016
Sounds like the 'StarWisp' but with a laser...

Wiki quote...
"Starwisp" is a concept for an ultra-low-mass interstellar probe pushed by a microwave beam. It was proposed by scientist and author Robert L. Forward in 1985,[1] and further work was published by Geoffrey A. Landis in 2000.[2] The proposed device uses beam-powered propulsion in the form of a high-power microwave antenna pushing a sail. The probe itself would consist of a mesh of extremely fine carbon wires about 100 m across, with the wires spaced the same distance apart as the 3 mm wavelength of the microwaves that will be used to push it.
5 / 5 (2) Apr 13, 2016
A question I have is how could the starcraft be decelerated? Also a minimum of 42 years would be more realistic when acceleration and deceleration are figure in.

Quote from article:
"If the new spacecraft were to achieve the proposed fifth of the speed of light, it would only take 21 years or so to get there (depending on the time taken to accelerate and decelerate)."

5 / 5 (9) Apr 13, 2016
A question I have is how could the starcraft be decelerated?

It wouldn't. The idea is to have them fly at 0.1c through the targetted system and acquire data along the way for the few hours/days they are in there.

Unless you set up a similar laser-system at the destination (read: not feasible) ...or set it on a course to crash into something in the target system (read: not particularly useful...and probably only feasible with the target star in any case)
Mark Thomas
5 / 5 (3) Apr 13, 2016
"But if the project is to bear fruit, where should these minute spacecraft be sent?"

We would only consider targeting Epilison Eridani or Tau Ceti first at 0.2c if there were nothing to see at Alpha Centauri, so let's cut to the chase here. Before we get serious about an interstellar probe, we really, really, really need to know what planets are in the Alpha Centauri system.

Suppose a new telescope like ATLAST discovers three near-Earth sized habitable zone planets around Alpha Centauri B, two around Alpha Centauri A and one around Proxima Centauri. For all intents and purposes, the debate would be over. Everyone would know the plan, regardless of which century it actually takes place in. That would be a great benefit to space exploration today because it would give us some much needed perspective. Mars doesn't look far at all when you are thinking about Alpha Centauri.
5 / 5 (2) Apr 13, 2016
ε Eridani
1.6 / 5 (7) Apr 14, 2016
Ln this case proximity was not a good choice.
The binary system (Alpha Centauri) has many unknowns (such as the effects of binary body to small body between them and whether there are any). For research to be chosen classic system, similar similar to ours.

The technology should be sought from the Voyager, which have accelerated in the cold space.
"The Oort cloud. Speed of light is not the limit !" http://www.svemir....html#9b

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