How far away from our system would Earth be detectable?

[willpittenger]

Could our current telescopes spot Earth from at least Alpha Centari? <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[nexium]

Some of the planet finding techniques might spot a possible Earth from 5 light years away, but Hubble perhaps could not resolve Earth for sure at 1/2 light year. That is just a guess. Neil

 

[vogon13]

The technology works both ways. We don't see planets there from here.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[brellis]

How accurately we have measured the 'wobble' caused by the various planets in our own solar system? Presumably such data is used to compare the mass and orbits of the extra-solar planets discovered in this manner.<br /><br />There was a recent announcement of a new telescope that will be able to measure "earth-shine" reflected from extra-solar planets, establishing some kind of estimate of their atmospheric composition.<br /><br /> <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>

 

[newtonian]

willpittenger - As Isaiah 40:17-23 accurately notes, earth and the nations are as an unreality when considering the expanding universe and our Creator.<br /><br />Depending on the distance, even from such a small distance, compared with distant galaxies, earth is like a film of dust on a scale or even as an unreality.<br /><br />Humbling - isn't it?! <br /><br />It is also amazing that God not only detects earth but also us as individuals - especially as it is likely He is probably viewing us from another universe!!!

 

[vogon13]

Newton's law of universal gravitation allows us to more accurately compute 'the wobble' (as you so quaintly put it) than it would be to try to observe the effects.<br /><br />{I think I know what you are asking, but you might be edging into 'aberation of starlight'. Sorry, it's late, I'm tired, and the comprehension skills are fading . . . .}<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[newtonian]

brellis - Also recent is the televising of plans to impliment a telescope that will be able to detect earth-type planets - but it is, if I remember correctly, but cause and effect rather than direction observation.<br /><br />As in observing the invisible by its effects.

 

[qso1]

As Vogon13 mentioned, Earth would be no more visible from Alpha Centauri than an earthlike world orbiting that system would be to us both using the current technology.<br /><br />As it currently stands, we have yet to image some of these several times the mass of Jupiter sized worlds that have been detected so far by radial velocity techniques.<br /><br />Another problem for planet hunting around AC is the fact AC is a binary system close in and a trinary when Proxima Centauri is included. Although Proxima would have little effect if any on gravitational factors within the periphary of the two main stars. But its the gravitational complexity of a binary system that would make radial velocity techniques more difficult to utilize in the search for earthlike or even earth sized worlds.<br /><br />This seems to be supported by the lack of any confirmed worlds orbiting the AC system so far. <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>

 

[qso1]

brellis:<br />How accurately we have measured the 'wobble' caused...<br /><br />Me:<br />IIRC, you are correct, they already do this because in general, they reference the tug Jupiter exerts on the Sun as a baseline for evaluating the mass of planets orbiting and affecting their parent stars.<br /><br />All exoplanets discovered so far have been detected by observed effects on the parent star. Radial velocity detects the wobble factor you mentioned and transit photometry detects a measurable drop in starlight when a planet passes between the star and our line of sight.<br /><br />There were a few direct observations of objects initially thought to be planets that later turned out to be brown dwarfs. The most noteable being the TMC-1 observation which in 1998 or 99 was thought to be a planet ejected from its parent star but later turned out to be another star.<br /><br />In the comment you made about earthshine detection, I think you probably meant starshine.<br /><br />No exo-planet has yet been directly imaged. <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>

 

[derekmcd]

What is the latest on this image<br /><br />As far as I know, this one still stands as legitimate, at least I couldn't find anything difinative against the claim... I could be wrong. <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[qso1]

http://www.space.com/scienceastronomy/050401_first_extrasolarplanet_pic.html<br /><br />The first story appears at the link above and as was the case with the TMC-1 thing. I withheld my judgement because I didn't believe TMC-1 was a planet. My reason, the object was said to be 130 billion miles from its parent star and TMC-1 was quite distant (Cannot recall how distant) from the system that imaged it which was HST. I couldn't believe even hubble would be capable of detecting reflected light from a planet 130 billion miles from its parent star even at near infrared wavelengths. It was later determined that the object was a distant star, apparently they watched it long enough to make that determination.<br /><br />As for the link above, the link is in reference to GQ Lupi which in the link below:<br />http://www.space.com/scienceastronomy/050430_exoplanet_image.html<br /><br />Is now headlined as being freshly debated. The problem lies within the excerpted text below:<br />Excerpt start:<br />Importantly, GQ Lupi is similar to our Sun, rather than being a dim brown dwarf star that emits virtually no visible light.<br /><br />But again there was a hitch: While observations suggest the planet orbiting GQ Lupi is about twice as massive as Jupiter, there is a slight chance it is 42 times the mass of Jupiter - so heavy that it would be considered a brown dwarf. The outlying models, however, are very unlikely to apply to the system, some astronomers said.<br />End exerpt.<br /><br />Me:<br />Basically, they are just not certain enough to my satisfaction to be able to truly claim they have imaged a planet as we currently understand planets. The outlying models being those approaching 42 Jupiter mass. The likelyhood IMO is that it may be 5-15 times Jupiter mass and would probably fall between pl <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>

 

[brellis]

hi qso,<br /><br />I was referring to earthshine in reference to a new telescope being designed. Serak_ made reference to it in the article I was thinking about in a post replying to you in the SETI section:<br /><br />" Qso1,<br /><br />Am enjoying the revival of this thread and am glad you seem to be, too. Thanks for an interesting discussion.<br /><br />More from Traub:<br /><br />Planet hunters bask in earthshine by Jonathan Amos (BBC)<br /><br />24 May 2006<br /><br />. . . Telescope technologies are being developed that will probe the very faint light from these [Earth-like planets] for tell-tale signs of biology.<br /><br />These are the same "life markers" known to be present in light reflected off the Earth - so-called "earthshine".<br /><br />They include signatures for water, and gases such as oxygen and methane.<br /><br />"This gives you some information on habitability," said Wesley Traub, chief scientist on the US space agency's (Nasa) Navigator Program which specialises in the search for far-off worlds.<br /><br />"These are only signs of life; they are only indicators. You can't actually detect the life itself crawling or sliming around on the surface of the planet," he told the American Geophysical Union Joint Assembly here in Baltimore, US.<br /><br />Traub is hopeful Nasa will approve the funds necessary to launch a Terrestrial Planet Finder (TPF) mission some time in the next decade...<br /><br />Anyway, you're right. What we need right now is a TPF or some similar space mission to start searching the infrared for the faint gleam of life. (Of course, TPF's fate may be hanging by a thread, and the Damoclean budgetary axe is plenty sharp...) " <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>

 

[qso1]

brellis:<br />These are the same "life markers" known to be present in light reflected off the Earth - so-called "earthshine". <br /><br />Me:<br />I see the difference now, thanks. I enjoy these types of discussions because its the holy grail of astronomy to find an earthlike world where the earthshine might reveal the presence of biological activity, perhaps even industrial or other activity associated with human level intelligent beings.<br /><br />brellis:<br />Anyway, you're right. What we need right now is a TPF or some similar space mission to start searching the infrared for the faint gleam of life. (Of course, TPF's fate may be hanging by a thread, and the Damoclean budgetary axe is plenty sharp...) "<br /><br />Me:<br />That budget ax is always sharp where NASAs concerned. While I would rather see a space based approach to the search for an earthlike world, I'm betting it'll eventually be ground based observation that nails it simply because NASA projects almost always get watered down and almost always get trimmed or deep fried in the budget mix. <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>

 

[agnau]

I smell a prize offering....

 

[derekmcd]

The link I posted is NOT GQ Lupi which I believe has been determined to be a brown dwarf binary. It is Star 2M1207A and its "planet" 2M1207b. Might be a bit confusing as it headlines with the GQ Lupi image. <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[willpittenger]

The question was how far aways you could <i><b>detect</b></i> Earth -- not see it. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[willpittenger]

You appear to have gotten my question all backwards. First, I asked if we could DETECT Earth -- not see it. Second, I was talking about detecting it FROM Alpha Centari -- not the other way around. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[doubletruncation]

I think it's largely a matter of how much observing time you'd be willing to spend on the thing. The current HARPS system seems to be stable enough to allow for sub m/s precisions from measurements over the course of several months, so if you spend enough time observing a particular star you should be able to get a precision of a few centimeters per second just from root N. I think it would be possible to detect an Earth-like planet around Alpha Centauri (if there is one) with present telescopes/instruments if you dedicated enough time to the project. I've heard it suggested that by putting such a spectrograph on a ~6 meter telescope it should be possible to determine the masses of candidate Earth sized planets in the habitable zone of other sun-like stars that might be discovered in the upcoming 5-10 years with Kepler with a reasonable amount of observing time (probably a few months worth of nights dedicated to the task with about 50 stars being targeted). Most of these stars would have magnitudes of about ~12 in the V band, so that would put them at a distance of up to about 300 pc away. Gravitational microlensing might allow for the detection of Earthlike planets at distances of several kiloparsecs, but there you have to rely on a much chancier alignments to detect them than you would to detect via radial velocity (or even to detect with transits). <div class="Discussion_UserSignature"> </div>

 

[qso1]

On detection, the answer is still probably no because we have yet to detect an earthlike world anywhere due to our inability currently to detect anything smaller than Neptune mass planets. In the spirit of your question, detecting Earth from Alpha Centauri may be on the very edge of possibility since AC is relatively close. We haven't detected anything there to my knowledge. <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>

 

[vogon13]

Did national comprehension skills drop sharply in the last week or so?<br /><br />4.4 lightyears is 4.4 lightyears whether you're looking through it back to front, or the other way round.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[willpittenger]

Qso was talking about the orbital complications of the overall Centari making it very difficult to detect anything there. Distance was not discussed. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[newtonian]

willpittenger - You asked:<br /><br />Could our current telescopes spot Earth from at least Alpha Centari? <br /><br />Your theme uses "detected."<br /><br /> That would, of course, include visible light along with the many other types of electromagnetic radiation observed by various telescopes.<br /><br />Planets, however, do not directly give off radiation like stars do - so naturally spotting planets is more difficult.<br /><br />See my previous posts.<br /><br />Qso's post were informative on the question certainly.<br /><br />I think the simplest answer is:<br /><br />NO, not yet.<br /><br />Especially no with regard to direct observation.<br /><br />Perhaps soon we will be able to detect by cause and effect earthlike planets at distances of less than 100 ly.

 

[thalion]

I don't think any current Earth or space-based telescope could find a Earth-mass planet in the habitable zone(s) of AC. That will have to wait for missions like Darwin, TPF, maybe GAIA, etc.

 

[agnau]

I wonder if an observatory placed on Pluto or Sedna might yield a good/better view of the AC system, if they are in the correct position they are much closer than Earth. Even then, could Pluto or Sedna spot earth in our own solar system if Hubble were orbiting one of them? <br /><br />If they can, spot earth, would it be similar to the way we see those bodies from here? Small and indistinct? If so, the answer to your question would be "No, not with current scopes".

 

[qso1]

Atually they would not be much closer at all. Keep in mind the AC system is well over 26 trillion miles away. Moving the scopes a distance of only 3.7 billion will make very little difference. Having said that, the advantage would be that the scopes would be clear of the inner solar system dust. Of course, if you can just get a telescope to the distance of Jupiter, you can be clear of the higher dust concentrations.<br /><br />Hubble could easily observe Earth from Pluto or Sedna. <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>