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Space Science

Earth's Corner of the Galaxy Just Got a Little Lonelier 224

Posted by Soulskill
from the and-a-little-safer-from-bloodthirsty-aliens dept.
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.'"
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Earth's Corner of the Galaxy Just Got a Little Lonelier

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  • Alpha Centauri (Score:5, Interesting)

    by Meneth (872868) on Wednesday August 22, 2012 @04:18AM (#41078847)
    What about Alpha Centauri? I suppose the binary nature of the star system could make it hard to detect any planets there.
  • by forkazoo (138186) <wrosecrans@gmai[ ]om ['l.c' in gap]> on Wednesday August 22, 2012 @04:29AM (#41078885) Homepage

    If a solar system has only one thing in it and that thing is mostly just relatively undifferentiated hydrogen, that's going to be less interesting that a solar system with a bunch of things in it. (Regardless of any ideas about colonizing or anything else.) It's certainly still possible that there is something fascinating in that solar system, but at the moment, it would have to be something we still can't detect, so it's hard to get as excited about. Planets are fascinating things. They have interesting geology and interesting compositions. They also imply that there is enough mass for things smaller than planets, like comets and asteroids as well.

  • by Taco Cowboy (5327) on Wednesday August 22, 2012 @04:43AM (#41078941) Journal

    A lack of planet on a nearby star does not mean there is nothing around the star

    There might still be fragments of ice / rocks / whatever that humankind can use to construct an artificial planet of some kind

    Plus, the lack of existing planet means we get to create one, with our own design

  • by invid (163714) on Wednesday August 22, 2012 @08:26AM (#41080061) Homepage
    By the time we have the technology to build our own planets, planets will be obsolete.
  • Re:Alpha Centauri (Score:2, Interesting)

    by Anonymous Coward on Wednesday August 22, 2012 @08:59AM (#41080485)

    How big a telescope would need to be, in order to be able to find streetlights on a planet 10 light years away, either by looking for an artificial spectrum, or for a frequency of the order of 50Hz, assuming a continent-wide synchronised AC power supply.

    Assuming you just want a big telescope that can resolve something on the scale of a streetlamp, 10 light years away...

    We'll need the small-angle formula and the Raleigh Criterion. The first gives us the angular size of the streetlight; the second gives us the diameter of the telescope needed.

    The small angle formula tells us D=a*d/206265, where d is the linear size of the object, a is the angular size, in arcsec, of the object, and D is the distance to the object.

    We'll assume a linear size of 0.25 metres and a distance of 9.46e16 metres (10 ly). This gives us an angular size of 5.45e-13 arcseconds.

    The Raleigh Criterion tells us sin(theta)=1.220*lambda/D, where theta is the resolution, in radians, lambda is the wavelength of the light source, and D is the diameter of the objective.

    Assuming a wavelength of 550nm, we get a diameter fo the objective of 2.54e11 metres, or 254 gigametres. For comparison, the earth's diameter is about 12 megametres; the diameter of Venus' orbit is 216 gigametres, and the diameter of Earth's orbit is 302 gigametres.

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