Earth to...Earth? Are you there?

jasamaman writes "So far all the planets found outside our solar system have been gas giants. So they are not habitable, and couldn't really hold life as we know it. But "planet hunter" David Charbonneau is looking for another planet just like Earth, and claims that astronomers are "very close"."

Comments

Microlensing transit events

[Cally]

People have been looking for microlensing events caused by IIRC the transit that yielded the first atmosheric compostition numbers, last year, had already been found by the parallax ("wobbly star") method used to find 99% of other known extra-solar planets. The orbital plane was already known to be in line with us, and indeed the event's timing was predicted using the wobbling parent star. The point is that this technique (which is really a hack in the original sense) is only any use in those rare cases where the orbital plane intersects line of sight from the parent star to earth. Calculation of the percentage of orbits for which this is true is left as an exercise for the reader (cos I haven't the maths ;) [Source: Astronomy magazine.)

Why we haven't found them yet

[Anonymous Coward]

The sun of our solar system contains more than 99,9% of its mass. Of the remaining 0,1%, most is of the megaplanets like Jupiter and Saturn. Jupiter alone has around 500 times the mass of Earth. Habitable plants are thus incredibly, incredibly small compared to their suns or compared to gas giants. Given the limited funding (forget space, we need missile defense!) we can be happy that we can detect gas giants.

Close, but not that close

[Pedrito]

There are a number of ways Earth-sized planets could be discovered fairly soon (within the next 5-10 years). There are several planet-finding satellites to be launched. The Hubble would also be capable of detecting an Earth-sized planet passing in front of a star.

The real trick is finding the proper conditions. First, we need to find an extra-solar system in which Earth-sized planets exist. It's now believed that these are fairly few and far between. The reason is that a vast majority of the gas giant systems we've discovered so far have their gas giants in either really close orbits to their stars, or are highly eliptical with passes close to their stars. In these situations, Earth-like planets would likely be tossed into their stars, or more likely, tossed into open space, by the gravitational effect of the giants.

So, what you need is giants that live fairly far out (like Jupiter and Saturn). These appear to be about 1 out of 50+ systems. So, out of this 1-2% of systems, we then need to find ones with orbital planes that are parallel to our angle of view of those systems, and catch the Earth-sized planets passing in front of their stars.

Asking for all those conditions to line up is a pretty tall order, so it's unlikely we'll catch such an event in the next 5 years. My personal opinion. A large breakthrough may change that, and that's possible as well. After all, look at the discovery of extra-solar planets. It was a breakthrough idea that led to a sudden discovery of many of these systems, without a real technilogical breakthrough.