I love Greg Laughlin’s remark to the Washington Post‘s Joel Achenbach in last week’s article Astronomers Seek New Home Closer to Home. Having discussed Debra Fischer’s ongoing search for Alpha Centauri planets and his own theories on planet formation around binary stars, Laughlin points out where we stand today: “We have what is to all appearances by far the best planet in the galaxy. And we have no workable backup plan.”
The Washington Post article doubtless draws on Lee Billings’ earlier piece in SEED Magazine called The Long Shot, which discusses with an elegance rare in science writing the attempt to find planets around the Centauri stars by Fischer as well as Michel Mayor’s Geneva team. Mayor has been using the High Accuracy Radial velocity Planet Searcher (HARPS) instrument at La Silla, the Cadillac of radial velocity instrumentation (and boy does that auto industry reference date me!). Competition can work wonders, and having two teams on the case can only bode well for quick results.
Not that those results will necessarily reveal planets, but we can hope for the best. Laughlin writes about the search in Alpha Centauri: Market Outperform, noting that “…when HARPS is working full bore on a bright quiet star, it can drill right down into the habitable zone.” Note, too, that Alpha Centauri is visible almost year-round from La Silla. Laughlin plugs in values for Centauri B’s habitable zone and creates data sets for differing values of planetary mass in the system. He then extrapolates from this to determine where the Geneva team might be now that it has upped its frequency of observations.
The results: A 4.6 Earth-mass planet in an optimally habitable orbit around Centauri B might be “…on the verge of current ‘announceability.'” A smaller 2.3 Earth-mass planet in the same zone would not be visible yet, requiring another year and a half of observations. If we’re anxious to find not a ‘super Earth’ but a true Earth analog, then, silence on the Centauri front for another eighteen months may, as Laughlin suggests, be good news.
But back to Laughlin’s comment to Joel Achenbach. At present, Earth’s lack of a backup plan is obvious, a matter of little concern to most unless we one day discover an asteroid in a dangerous, intersecting orbit. What technologies do we have today that could move quickly to reach an object potentially far out in the Solar System, allowing us to change its trajectory? Making sure we have the tools is part one of the backup plan, and that puts an emphasis on observation and propulsion studies.
Part two is building the infrastructure for a continuing human presence off-planet, and for ensuring that future asteroid or comet encounters are better anticipated. Part three is finding out whether continuing work on interstellar propulsion will one day produce the energies we need to push a payload to the nearest stars in time frames that human crews can survive. The answer will determine whether our backup plan is system-wide or extends to habitable planets around suns other than our own.