Telescopic Detection in the detection of extra solar earth’s has proven not to be feasible for a couple of reasons: Planets are not bright objects, they are only detectable using optics when there is enough reflective light from a nearby star, and the brightness of a star often dwarfs the visual image of a planet, hiding it from view. These restraints have made it impossible to view these possible extra-solar planet candidates detected through planetary “wobbling” via conventional telescopes. An often used analogy that is used to compare this difficulty of observing extra-solar planets is that of a car headlight. Imagine a small coin a few inches away from a car headlight. Then think of how hard it would be to read the date of that coin when standing far away, say 50-100 ft. It would be impossible. The faintness of the planet and the brightness of the star make viewing extra-solar planets through optical conventional telescopes just that, impossible.
However, astronomers have developed two methods of detecting gravitational influence that is the trademark, in theory, of extra-solar planets: astrometric and radial velocity detection. Astrometry is the method of observing a star’s relative position to the distant stars in the background. Over time, observations of the changes in its positions can reveal information about the orbiting bodies. Radial velocity, on the other hand, relies upon the principle of gravity but is a totally different measurement. It depends on the Doppler shift. If a planet pulls a star slightly away from earth, longer wavelengths are observed through radio telescopes. If the orbiting body pulls it closer to earth, than a blue shift, or shorter wave length radio wave is observed. Astronomer’s choose a known spectral line and compare that to the star’s in order to receive an accurate hypothesis of the Doppler shift.
The next logical step in the progression of extra-solar planetary detection is direct detection of these orbiting bodies, but as stated formerly, that is not feasible at our present state in technology. The efficiency with which a telescope gathers radiation is the key component to this. Consider the fact that the optical limitations of the Hubble Space Telescope and the proposed Space Infrared Telescope Facility. From one of the closest stars to our solar system, it would be impossible to distinguish Jupiter from the sun. From the bases of possibly the most advanced telescopes available at the time it would be impossible to decipher because Jupiter’s distance from the sun is smaller than the image’s size. The planetary body would literally be included as part of our sun. It is because of these limitations that future detection is only seen possible through the infrared using interferometric techniques.
Currently, there are plans to develop the Millimeter Array (MMA), a ground based telescope devised to observe the wavelengths from 7 mm to 350 microns. This telescope, supposedly to be built like its parent one in Chile, could aid in the detection of massive protoplanets and of gas disks surrounding young stars. Here, the resolution would be able to image the star and the giant planetary companion. Eventually, with the help of an upgraded Very Large Array (VLA) telescope, comprehension of the development of young planetary systems will be greatly improved.
Bibliography: “Detection and Imaging of Extrasolar Planetary Systems at mm/submm Wavelengths”. www.aas.org/publications/baas/v27n4/aas187/S070016.html “Extra Solar Planet Detection”. Isi9.mtwilson.edu/~david/planets.html Strategy for the Detection and Study of Other Planetary Systems and Extrasolar Planetary Materials: 1990-2000. www.nas.edu/ssb/detectionich5.htm#observational