Originally posted by Stari
reply to post by yeti101
Agreed, their probably are more planets around Centauri B. Hopefully it won't take to much longer for them to find them all now
The problem is that using the method used to find this planet (the Doppler Spectroscopy/Radial Velocity method), it is easier to find planets orbiting
close to a star, but more difficult to find planets orbiting farther out from that star.
Doppler spectroscopy detects the minute wobble in a star caused by the gravitational tug of an orbiting planet. Generally
, the closer the
orbit, the larger the wobble. Planets farther out cause a more minute wobble, and are thus harder to detect.
There is also the "Transit Method" for detecting extrasolar planets. That method looks for a planet moving in front of a star, and thus causing the
star to dim ever-so-slightly. This method requires that the planet actually DOES move in front of its star as seen from our viewpoint on Earth
I'm not sure if the transit method could be used for Alpha Centauri B, because I don't know it the planets are lined up in such a way that they DO
pass between its star and Earth.
Even if they do, the transit method again works best for planets orbiting VERY close to a star (therefore, maybe very hot), because scientists using
the transit method usually like to confirm a planet's existence by watching it pass in front of the star several times -- and passing in front of the
star several times for a planet orbiting farther out from its star may take years to confirm...
...For example, if some aliens from another star system were using the transit method to detect earth, they would only see it pass in front of our
Sun once per year.
Using the transit method, a scientist may "think" a planet might exist based on only one transit (one planetary pass between the star and earth), but
it takes at least three transits to get better confirmation of the planets existence -- i.e., the time span between multiple transits would be the
same, giving some confirmation. Again, using the example of some aliens trying to detect earth with the transit method, it would take just over two
years to detect three transits.
edit on 10/19/2012 by Soylent Green Is People because: (no reason given)