[LINK] Two Centauri Dreams links on Alpha Centauri Bb

[rfmcdonald]

There's an odd sort of symmetry in the title of this post, isn't there? Centauri Dreams' Paul Gilster has good coverage of Alpha Centauri, as one might expect given the title of the blog.

The first post, "Reflections on Centauri B b", is a reflection on any number of subjects, centering on the suitability of Alpha Centauri B as a subject for astronomical observation and as a host for worlds with Earth-like environments.

At the news conference, Laughlin likened our current state to halftime at a football game. We’ve pulled out a major detection but even as we start to speculate about rocky worlds further out in the system, we’re faced with increasingly difficult observations. We can expect the Alpha Centauri story to unfold slowly, but Xavier Dumusque (Centro de Astrofísica da Universidade do Porto) pointed out how much more difficult it becomes to find planets as we move further out in the Centauri B system, adding that it would take at least twice as many measurements as the Geneva team has now made. Right now the researchers are saying the HARPS spectrograph might be limited to a planet with a lower mass limit of about four Earth masses here, but Stéphane Udry added that new ESO instrumentation was in the works that offered, in the not so distant future, good prospects for finding an Earth-mass planet in the habitable zone.

A 230-day orbit around Centauri B should put us right in the middle of the habitable zone, the place we’d most like to find a terrestrial world. Fortunately, it’s a region of orbital stability — the effects of Centauri A only become problematic as we move as much as 3 AU out from the star. Before we can find a habitable zone planet, we’ll need to confirm Centauri B b and begin to study it, which is where that useful transit could come in. The probable picture is stark — a rocky, lava-world with a surface temperature somewhere around 1500 Kelvin, surely in a tidally locked orbit. Not exactly a clement place, but the implication of other worlds in this system will urge us forward.

The second post, "Centauri B: Targets and Possibilities", considers the prospects for a mission to ASlpha Centauri, especially if some passingly Earth-like world is found. The prospects, as yet, are distant; interstellar flight is far out of our league at present.

Voyager 1, now 17 light hours from Earth, continues to be my touchstone when asked about getting to Alpha Centauri — and in the last few days, I’ve been asked that question a lot. At 17.1 kilometers per second, Voyager 1 would need 74,000 years to reach the blistering orb we now believe to be orbiting Centauri B. Voyager 1 is not the fastest thing we’ve ever launched — New Horizons at one point in its mission was moving with greater velocity, though no longer, and the Helios II Solar probe, no longer functional, reaches about 70 kilometers per second at perihelion. But Voyager 1 will be our first craft to reach interstellar space, and it continues to be a measure of how frustratingly far even the nearest stars happen to be.

Cautionary notes are needed when a sudden burst of enthusiasm comes to these subjects, as it seems to have done with the discovery of Centauri B b. What we need to avoid, if we’ve got our eyes on long-term prospects and a sustained effort that may take centuries to succeed, is minimizing the challenges of an interstellar journey. Making it sound like a simple extension of existing interplanetary missions would create a public backlash once the real issues become clear. Better to be straightforward, to note the vast energy budget needed by an interstellar mission, the conundrum of propulsion, the breathtaking scope of the distances involved.