Earth's Corner of the Galaxy Just Got a Little Lonelier 224
Hugh Pickens writes "Only four stars, including Barnard's Star, are within six light-years of the Sun, and only 11 are within 10 light-years. That's why Barnard's star, popularized in Robert Forward's hard-SF novel Flight of the Dragonfly, is often short-listed as a target for humanity's first interstellar probe. Astronomers have long hoped to find a habitable planet around it, an alien Earth that might someday bear the boot prints of a future Neil Armstrong, or the tire tracks of a souped-up 25th-century Curiosity rover. But now Ross Anderson reports that a group of researchers led by UC Berkeley's Jieun Choi have delivered the fatal blow to those hopes when they revealed the results of 248 precise Doppler measurements that were designed to examine the star for wobbles indicative of planets around it. The measurements, taken over a period of 25 years, led to a depressing conclusion: 'the habitable zone around Barnard's star appears to be devoid of roughly Earth-mass planets or larger ... [p]revious claims of planets around the star by van de Kamp are strongly refuted.' NASA's Kepler space telescope, which studies a group of distant Milky Way stars, has found more than 2,000 exoplanet candidates in just the past two years, leading many to suspect that our galaxy is home to billions of planets, a sizable portion of which could be habitable. 'This non-detection of nearly Earth-mass planets around Barnard's Star is surely unfortunate, as its distance of only 1.8 parsecs would render any Earth-size planets valuable targets for imaging and spectroscopy, as well as compelling destinations for robotic probes by the end of the century.'"
Re:And why should we be looking for "Earth-size" ? (Score:2, Informative)
Because if it's larger then gravity will make it uninhabitable, and if it's smaller then it can't hold an atmosphere, which again would make it uninhabitable.
Re:No planets around Barnard's Star? (Score:2, Informative)
For a moment there, I thought you meant on the other side of the moon from us, rather than from the base. I was already to go "nooooo, that'll crash it into the Earth, you fool!" Then I realised. And posted anyway. Ah well.
yes, that's the ridiculous part of the "nuclear powered moon-ship" plan.
Re:No planets around Barnard's Star? (Score:3, Informative)
It's called "A Pail of Air" by Fritz Leiber from 1951.
The planet was actually earth, which had been torn away from the Sun by a dark star passing through.
It's a nice and rather short story and can be read in full here. http://www.baenebooks.com/chapters/0743498747/0743498747___6.htm [baenebooks.com]
Re:Look at the bright side (Score:5, Informative)
capable of artificial gravity,
You want some faster than light travel with that? Or perhaps telekinesis?
Inertia expressed as centripetal force will do just fine, thanks.
Re:Is it still a possibility? (Score:5, Informative)
The barycenter of sun-earth is only 300 miles from the middle of the sun.
Keep in mind that Barnard's star is only about a seventh of the sun, and much cooler, so the habitable zone is much closer. An earth sized planet in the habitable zone would have a much larger impact on Barnard's Star than Earth does on Sol.
Results did not rule out Earth sized planet (Score:4, Informative)
A lack of planet on a nearby star does not mean there is nothing around the star
And, even more to the point, a lack of a planet larger than ten times the Earth's mass in an Earth-like orbit, or two times Earth's mass in a close-in (ten day) orbit says nothing about the presence or absence of Earth- mass planets, unless you have a well-accepted theory showing that systems with Earthlike planets must also have Jupiter-like planets, which is a theory we don't have.
That's according to what the actual article says-- ignore the Slashdot summary, it's wrong. http://arxiv.org/abs/1208.2273 [arxiv.org]
And, worse, the mass detection limits are limits on m*sin(i)-- if the orbits are inclined, the planet masses that couldn't be detected would be even larger. (in the limit, if the orbit is face on, it wouldn't have detected planets regardless of how massive they are)
Overall conclusion: This puts limits on planets around Barnard's star, but did not have the ability to detect, and thus did not rule out, Earth-mass planets.