An astro-comb to detect extrasolar Earths

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doubletruncation

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<p>There was a very interesting article in Nature this week about a new technique that may enable people to measure the radial velocities imparted to Sun-like stars by Earth-sized planets. The news summary is at:</p><p>&nbsp;http://www.nature.com/news/2008/080402/full/452514b.html</p><p>and a free version of the paper is at:</p><p>&nbsp;http://arxiv.org/abs/0804.0955</p><p>The paper's abstract:<br />"Searches for extrasolar planets using the periodic Doppler shift of stellar spectral lines have recently achieved a precision of 60 cm/s (ref 1), which is sufficient to find a 5-Earth-mass planet in a Mercury-like orbit around a Sun-like star. To find a 1-Earth-mass planet in an Earthlike orbit, a precision of 5 cm/s is necessary. The combination of a laser frequency comb with a Fabry-Perot filtering cavity has been suggested as a promising approach to achieve such Doppler shift resolution via improved spectrograph wavelength calibration, with recent encouraging results. Here we report the fabrication of such a filtered laser comb with up to 40- GHz (1-A) line spacing, generated from a 1- GHz repetition-rate source, without compromising long-term stability, reproducibility or spectral resolution. This wide-line-spacing comb, or `astro-comb', is well matched to the resolving power of high-resolution astrophysical spectrographs. The astro-comb should allow a precision as high as 1 cm/s in astronomical radial velocity measurements."</p><p>So it looks like they've taken a big step toward being able to detect planets like the Earth orbiting other stars from the ground. This will also be really important for space missions like Corot and Kepler which hope to detect these planets via the transit technique. Previously it wasn't clear that any candidate new Earths found by these missions would be confirmable, now it seems like it might be possible. Also knowing both the mass and radius of these things will be key to inferring the properties of the planet.</p> <div class="Discussion_UserSignature"> </div>
 
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qso1

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<p>As interest in finding earthlike worlds spread, more techniques become available. I always hoped there would be a technique available to earthbound astronomers because depending on space based alone is still a dicey proposition at best considering budget problems, even occassional LV problems or spacecraft problems.</p><p>Best to have both space based and ground based capabilities.&nbsp;</p> <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>
 
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origin

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<p>well this is over my head but it sure sounds great to be able to detect planets to this level of precision.&nbsp; It seems with this type of measurement techinique you could even detect the planets&nbsp;orbiting&nbsp;very distant stars.</p><p><br /><br />&nbsp;</p> <div class="Discussion_UserSignature"> </div>
 
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qso1

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And the best part about that is current methods have detected planets well beyond 50 light years out. Being able to detect earth like worlds within say a 100 ly radius would help to determine how common they are. Specifically how common earthlike worlds that are more earthlike than Mars and Venus. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>
 
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weeman

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>There was a very interesting article in Nature this week about a new technique that may enable people to measure the radial velocities imparted to Sun-like stars by Earth-sized planets. The news summary is at:&nbsp;http://www.nature.com/news/2008/080402/full/452514b.htmland a free version of the paper is at:&nbsp;http://arxiv.org/abs/0804.0955The paper's abstract:"Searches for extrasolar planets using the periodic Doppler shift of stellar spectral lines have recently achieved a precision of 60 cm/s (ref 1), which is sufficient to find a 5-Earth-mass planet in a Mercury-like orbit around a Sun-like star. To find a 1-Earth-mass planet in an Earthlike orbit, a precision of 5 cm/s is necessary. The combination of a laser frequency comb with a Fabry-Perot filtering cavity has been suggested as a promising approach to achieve such Doppler shift resolution via improved spectrograph wavelength calibration, with recent encouraging results. Here we report the fabrication of such a filtered laser comb with up to 40- GHz (1-A) line spacing, generated from a 1- GHz repetition-rate source, without compromising long-term stability, reproducibility or spectral resolution. This wide-line-spacing comb, or `astro-comb', is well matched to the resolving power of high-resolution astrophysical spectrographs. The astro-comb should allow a precision as high as 1 cm/s in astronomical radial velocity measurements."So it looks like they've taken a big step toward being able to detect planets like the Earth orbiting other stars from the ground. This will also be really important for space missions like Corot and Kepler which hope to detect these planets via the transit technique. Previously it wasn't clear that any candidate new Earths found by these missions would be confirmable, now it seems like it might be possible. Also knowing both the mass and radius of these things will be key to inferring the properties of the planet. <br />Posted by doubletruncation</DIV><br /><br />"Have you finished combing the galaxy yet?"</p><p>"Man, we ain't found sh*t!"</p><p><img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-smile.gif" border="0" alt="Smile" title="Smile" /><img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-laughing.gif" border="0" alt="Laughing" title="Laughing" /></p> <div class="Discussion_UserSignature"> <p> </p><p><strong><font color="#ff0000">Techies: We do it in the dark. </font></strong></p><p><font color="#0000ff"><strong>"Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity.</strong><strong>" -Albert Einstein </strong></font></p> </div>
 
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MeteorWayne

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>"Have you finished combing the galaxy yet?""Man, we ain't found sh*t!" <br />Posted by weeman</DIV></p><p>Somehow, Spaceballs comes to mind....<img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-wink.gif" border="0" alt="Wink" title="Wink" /></p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>
 
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