planet detection

[MeteorWayne]

Andrew, over short periods, indeed the noise levels are large, but over long periods, the signal clearly comes through.<br /><br />The earth is a very stable platform as we understand it's motion so well. <br />I do recall that the first attempts at radial velocity detection failed to correct for all the factors and a false planet was proposed, but as it goes in science the error was found in short order and a retraction was issued.<br />Since then, with over 200 planets detected by this method, they've had plenty of practice, and the process is quite refined.<br /><br />Atmospheric aberration doesn't give false readings.<br />Remember, the radial velocity that is being measured is not being measured by something like a radar reflection that the atmopshere can effect. So it's not velocity in the intuitive sense. The measurement is based on the shift in spectrum of the star (red shift and blue shift), which the atmopshere does not effect.<br /><br />So while spacecraft can do the measurement, it is not required at all.<br /><br />MW <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>

 

[qso1]

alokmohan:<br />Agreed .How do you know if something is a brown dwarf or not?Thy may have boder line cases.<br /><br />Me:<br />Thats probably a little more difficult to determine and I suspect the line between planet and brown dwarf will be somewhat blurred. Currently the temperature estimates give some indication. And if I were an astronomer, one criteria would be that the BD emit its own light. This would be an indication of some level of fusion being sustained within the BD. Eventually, direct imaging should reveal which planets are glowing like stars and which simply reflect starlight. <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>

 

[3488]

Hi MeteorWayne.<br /><br />It is very rude of me not to reply sooner. <br /><br />Thank you very much. Of course, we are not dealing with resolution, rather Doppler <br />shifting on the parent star & as both the Earth's & Sun's movements are well known, they <br />can be eliminated from the readings. <br /><br />Whilst I was not sure of the validity of many claims, your explanation has<br />banged me to rights.<br /><br />Mind you, I can't wait to see more IR spectra from the planets themselves,<br />we will then see what type of objets we have found<br />& see whether or not the gas giants of our solar system<br />are typical!!!<br /><br />Once again Thank you very much.<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[3488]

Hi alokmohan.<br /><br />Yes , you are correct. AFAIK, in many cases, it is <br />the minimum mass of the object that has been determined (assusming we are looking at the exoplanet, <br />along the path of its orbit or its 'ecliptic'.<br /><br />Of course some giant Jovian worlds may actually turn out to be Brown Dwarfs, if observations later,<br />on show that we are looking onto the system, from<br />a high latitude or even polar (like Vega / Alpha Lyrae).<br /><br />The distinction as qso1 correctly said cannot be a fine line.<br /><br />Imagine two giant planets lets say, one with a mass of 19.9994 times that of Jupiter & <br />another 20.0003 times that of Jupiter. Is one a Jovian planet & the other a Brown Dwarf????<br /><br />Difficult one really.<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>