Thursday, March 12, 2009
Exoplanets How do we find these itty bittys?
Growing up in the sixties and seventies Space was a part of your life. There was always something going on. Satellites or manned space vehicles were coming and going at a frightful pace. Even on TV Lost in Space, Star Trek to name a couple. Now as a kid watching these shows I just knew there were other planets circling around some distant star. I just knew it had to be true. I had a discussion with my teacher over this at one point. I remember him telling me "Steve there is no proof that there are any other planets save the nine( Yes! I said nine ) we have around the sun." Oh sure throw out the old scientific proof block. Sure there was some work done in 1952 by Otto Struve about how to find exoplanets. Not many took stock in the method preposed (a thing called radial velocity) that is until our instruments got much more sensitive...and so it stayed. Proof proof proof. Humbug! Then in 1995 The little boy pulled his finger out of the Dyke. We had proof! and the numbers of new Planets started to roll in. 340 plus and climbing fast Folks!!! Doppler spectroscopy (also called the Radial velocity method) Hmm... That rings a bell! was the first method used to find an exoplanet. We heard someone say way back. Hey we might be able to detect the planet by looking at the spectrum of the star and looking for a red shift. If found we have a force pulling on the Star causing it to wobble back and forth. The spectral lines will move back and forth and Holy Guacamole we have found a planet! Congrats to Didier Queloz and Michael Mayor for being the first. Here is a twist to it. Radial velocity of the object (how fast it moves back and forth can tell us orbital period of the planet as well as how big the puppy is!!! And to think in School I chose Home ec over Calculus (more girls in the Home ec class). Should have rethought that one. Then there is Astrometry Pretty simple we check the position of the star in question in the sky if something is tugging on it (a Planet) it will wobble in its position tiny as it is we can detect it and we will see it! well not seeee it but we know it is there. Keep in mind no planet has been found yet by Astrometry Yet... These methods find big Jupiter sized planets within say three AU (1 AU is equal to 93 million miles or so or the average distance to the sun from Earth) Is your brain hurting yet? Cause we are not done. Photometry is another way to find these other worlds. If the star being observed has a periodic loss of brightness 2 to 5 percent we monitor the pattern and bingo! we just might have a winner. This one only works on the stars that have planets eclipsing them from earths point of view. These suspects are usually run through the other methods to confirm. Then there is Gravetational Microlensing I know wow! What the Hooey dooey is that? It a method using Two stars lined up but far off from one another as the far one passes behind the "Target " star the Fore ground star appears to get brighter (because it is bending the stars light behind it around the fore ground star and adds it to it's own when a planet is there also there will be a extra bump of light in the detection ah!!! Thats how it is done or so I'm told :) Now I know what you are thinking. You need to SHOW me a planet not some danged ole graph and a couple of ciphers. Folks have been searching for that elusive Kodak moment for some time. The wait is over! We now have the pictures to prove it. This is a very cool thing that has happened in that this is something that we can get our heads around. A picture but Whoa there partner not a picture, but two, one showing multiple planets!!! The multiple planet pix is in infrared and these beauties show up nice as they are still cooling after forming some 60 million years ago! The other is in visible light of a planet? circling Formalhaut. Now Brother and Sisters I am impressed. These are exciting times we live in Astronomically speaking. So I guess I just wanted to say to my Teacher so long ago... Told ya so!
Clear skies and good seeing too!