Kepler Mission Options

[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...

[AndyG]

.
HAT-P-2 b -> ~11.9 g cm^-3.

Denser than lead? That - Jovian cores aside - doesn't seem very planet-like to me.

Andy

[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!!

[SpaceListener]

... can use the Keck-calculated mass ...

That has brought to my attention. How does the team determine its mass?
Using the mass spectometry determines it? If it is so, which of the following
method uses:

a) Vaporisation
'b)' Ionisation
c) Acceleration
d) Deflection
e) Detection


Regards,

[dilo]

SpaceListener, I hope you're jocking...
If you are able to put an exoplanet inside a mass spectrometer, you are a genius!

[djellison]

How does the team determine its mass?

I assume by the scale of it's influence on the parent star.

Doug

[Guest_PhilCo126_*]

Correct Doug... examining the star's (periodic) radial velocity(ies) reveals the mass(es) of exo-planet(s).

AdyG --> http://en.wikipedia.org/wiki/HAT-P-2b

Multiple exo-planets:

[siravan]

Correct Doug... examining the star's (periodic) radial velocity(ies) reveals the mass(es) of exo-planet(s).

Using radial velocity technique, one can calculate m.sin(i), where m is the mass and i the orbital inclination (for one or more planets). Hence, the radial velocity only determines a lower limit on the mass. If an exoplanet is observed by both radial velocity and transit method, it means i=90 (due to seeing a transit), and that fixed the mass. Planet radius can be calculated by transit method. Therefore, using a combination of radial velocity and transit methods, it is possible to calculate the density (but neither does it alone).

[Mongo]

One unexpected (to me) fact is that using a planet's transit light curve and its primary's spectroscopic orbit (radial velocity), one can calculate the planet's surface gravity directly, as opposed to indirectly via mass and radius. This was discussed in this thread from a couple of years ago.

[Vultur]

When will Kepler begin to actually observe stars?

[Mongo]

According to the Kepler twitter site, it will be another 50-60 days before science operations start, so early to mid May.

[Stu]

Anyone wanting to read some background info about - and comments from people involved in - the Kepler mission should check out Ustrax's new blog, Beyond The Cradle. Some really good stuff on there, written by one of our most passionate and enthusiastic members. He's also been kind enough to use my latest poem, which was inspired by Kepler's mission.

http://beyondthecradle.wordpress.com

[ustrax]

You're too kind my collab...friend...

Vultur and Mongo, Natalie Batalha told me that the next crucial event will be to eject the dust cover, that's when Kepler will get its first-light image, this will take place two weeks from now, on the 26th...that also when Batalha's will make her appearance at the blog...