Kepler Mission Options

[imran]

This NASA Discovery mission is to be launched in June 2008 and will search for Earth-size and smaller planets. Launch was originally scheduled in 2007 but delayed by 8 months due to "funding constraints".

Here's the official web site:
http://www.kepler.arc.nasa.gov/

[Guest_PhilCo126_*]

Talking about mission life time; there was already talk of a possible extension to six years, which would allow improved observations of more transits to detect smaller planets and of course finding planets in larger period orbits

Meanwhile:
http://www.astronomynow.com/090310KeckandK...joinforces.html

[HughFromAlice]

improved observations

Ref the article: Interesting!!! Especially ..... "Furthermore, Marcy and his team can use the Keck-calculated mass and Kepler-calculated diameter to determine the planet's density". (My bolding)

[Hungry4info]

Ref the article: Interesting!!! Especially ..... "Furthermore, Marcy and his team can use the Keck-calculated mass and Kepler-calculated diameter to determine the planet's density". (My bolding)

I am unsure why you bring attention to this. Density = mass / volume, with the mass and volume of a planet, we can calculate its density fairly easily. The density of transiting planets is not unmeasured.
To name a few examples:
HD 209458 b -> ~ 0.41 g cm^-3.
HD 149026 b -> ~ 0.82 g cm^-3.
HAT-P-2 b -> ~11.9 g cm^-3.
HD 189733 b -> ~ 1.06 g cm^-3.
TrES-3 b -> ~ 0.99 g cm^-3.

And so on...

[HughFromAlice]

I am unsure why you bring attention to this.

As I understand it (being an interested amateur) the radius of planets can only be determined from the shape of their light curves using transiting techniques. Since Kepler will be in space and has such an advanced photometer, it will be able to determine the size of planets that are even smaller than Earth. It will simultaneously observe a huge number of stars - 100,000.

Before reading the article I didn't realize that there was any radial velocity technique sensitive enough to check out the mass of such small planets. Since Keck has the capability to detect changes in radial velocity down to below 1/m sec, it is senstive enough. It will target the transit positives.

So you were right to comment!!! Currently we only know the size and and mass of a small percentage of planets - the new Planetary Society exoplanet catalogue is really useful resource. What I should have said was ...... density of (hopefully a lot of) earth like planets!!!. That's exciting. How many will be around the 5.75 gm/cc? I believe radial velocity techniques currently only estimate min mass with + ~20% error range to more heavy than estimated - worse if not in line of site.

PS - Andy - TPS catalogue gives HAT-P-2 b density ~13.37 gm/cc!! 'Super Earth' CoRoT-Exo-7b density ~11.36 gm/cc!!