A Civilization Changing Event

Finding an Earth-like or even a Earth-sized planet would be considered a civilization changing event. It would mark a pivotal point in human history where the proof of planets like the Earth exist with direct implications that our galaxy and the universe is filled with planets similar to our own. And the inevitable conclusion that life, and intelligent life is a certainty.

Indeed a small, but powerful, telescope operated by David Chabonneau at Harvard, paper here, has recently reported the discovery of a 6 Earth mass planet orbiting a nearby red dwarf star. The MEarth telescope is an array telescope composed of 8 off-the-shelf 0.4m instruments with off-the-shelf cameras. The discovery of this planet took only a few months of work. The MEarth telescope observes some 2,000 red dwarf stars. The OMI could easily monitor several hundred thousand red dwarf stars and would have a high probability of discovering an Earth-sized planet.

The Core long term science project of the OMI is to detect Earth like planets around red dwarf stars. These stars comprise some 80% of the total galactic population. They are exceedingly dim and are about 10% the diameter of the Sun. An Earth size planet would be about 8-10% the diameter of this type of star and this fact is what makes them detectable by a technique called a transit, where a planet crosses in front of its star as seen from the Earth. This causes a slight dimming of the star which can be measured. Now the orbit of the planet has to be aligned in such a way that the crossing of the planet in front of the star can be seen from Earth. This only happens in a small percentage of these stars. Also the transit only last a few hours. The amount of dimming is directly proportional to the ratio of the planets' disc to the stars' disc.

In order to increase the probability of detection you need to observe as many stars as possible, over and over again. The OMI's wide field of 2.22 x 2.22 degrees coupled with its 1-metre aperture with a high performance digital camera and a very dark site make it a good instrument to attempt this.

We expect the OMI with a 1σ 0.001 mag in 2000 seconds exposure for a 17^th magnitude star (r'). At galactic latitude of 20º there are about 3,000 stars per square degree to 17^th magnitude (Bahcall and Soneira 1980). In a single exposure covering approximately 5 square degrees we would expect >15,000 stars per image for which we could possibly detect Extra Solar Planet (ESP).

Transit of an hypothetical Earth-like planet and a red dwarf star.

This diagram shows the limit of photometric precision needed to detect various bodies in orbit around F, G, K and M dwarf stars. The lines represent planets of sizes equal to Jupiter, Neptune, and the Earth. For ground-based telescopes, Jupiter-sized bodies are easily detected around all of the spectral types plotted here, Neptune-sized bodies are likely detectable for G-M stars, and earth-sized bodies may be detectable for late M stars (from Photometric Search for Extra-Solar Planets. S. Howell and M. Everett, University of Wyoming).

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