Exo-planets

[adering]

So the latest planet discovered, Gliese c, has about 2.2 times the gravity of Earth. A bit heavy. <br /><br />Almost all of the exos on the lists so far are about Jupiter-sized or bigger. <br /><br />Is it that we <i />don't have</i> the ability to find Earth-sized planets with Earth-like gravity, orbiting in the liquid water zone of their respective stars except under "hole-in-one" conditions? <br /><br />Or is it that we <i />should</i> be finding them left and right and all over the place but they just <i>aren't turning up</i>?

 

[MeteorWayne]

Welcome to Space.com!<br /><br />We don't yet have the ability do discover earth sized planets in earth like orbits. We're getting there.<br /><br />The primary discovery method is radial velocity measurement. This is where the mass of the planet pulls the star back and forth as it revolves around the star, and we measure the red and blue shift of the light as the star approaches us and moves away. A very tiny bit <img src="/images/icons/wink.gif" /><br />So it is most sensitive to large planets, in short period orbits.<br />That moves the star back and forth more, and the cycle repeats more often so you can see multiple cycles.<br /><br />If someone was observing our solar system for the amount of time we've been looking with this technique, they just might have a suspicion (but would be unable to prove) that Jupiter exists, since Jupiter has an 11.8 year orbit.<br />The sun's reflex motion is dominated by Jupiter (49% of the motion, 11.8 Year period), Saturn (27% of the motion, 29.7 Years), Uranus (8% of the motion, 84 years), and Neptune (15% of the motion, 164 years). So it would take hundreds of years just to confirm that Jupiter and maybe Saturn exist, and a thousand years for Uranus and Neptune.<br />All the rest of the planets, comets, asteroids accound for only 0.4% of the motion with periods from 1/4 year to hundreds of years. They likely would take many thousands of years to dig out of the data, once the orbits of the 4 major planets were known.<br />So bluntly, there is no way we would be able, by this method, to have possibly detected the earth even around the nearest star.<br /><br />If, on the rare chance that earth would transit the sun (pass between the sun and the observer, the alignment has to be almost perfect) the reduction in light caused by the earth would be much too small to detect.<br /><br />Hope that helps you understand. <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]

Ya beat me to the punch, LOL.<br /><br />Excellent explanation and probably better than I could have said it anyway. <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>

 

[alokmohan]

Viewing Vulcan<br /> Summary (May 16, 2007): Astronomers have concluded that NASA's upcoming SIM PlanetQUest mission will be able to search for Earth-like planets 16 light-years away. SIM PlanetQuest could be followed by the Terrestrial Planet Finder mission, which will be powerful enough to see distant planets and scan them for signs of life.<br /><br />Display Options: <br />--------------------------------------------------------------------------------<br /><br /><br /><br /><br />Viewing Vulcan<br />Based on a NASA news release<br /><br />Science fiction may soon become science fact.<br /><br /> <br />The Enterprise orbiting the fictitious planet Vulcan. (Star Trek images courtesy STARTREK.COM, Copyright 2007 CBS Studios Inc.) <br /> <br />Astronomers at NASA's Jet Propulsion Laboratory have recently concluded that the upcoming planet-finding mission, SIM PlanetQuest, would be able to detect an Earth-like planet around the star 40 Eridani, a planet familiar to "Star Trek" fans as "Vulcan." 40 Eridani, a triple-star system 16 light-years from Earth, includes a red-orange K dwarf star slightly smaller and cooler than our sun. Vulcan is thought to orbit that dwarf star, called 40 Eridani A.<br /><br />When pondering the idea that SIM might be able to detect Vulcan, astronomer Dr. Angelle Tanner at Caltech had two questions: Can a planet form around 40 Eridani A? Can SIM detect such a planet? She consulted a planetary theorist, Dr. Sean http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=2333&mode=thread&order=0&thold=0<br />