Stargazing Kepler Telescope Views Single Point in Space 4.2ly Away

[bill ginger]

Astronomers are viewing a single point in space (.1 arcseconds), using the Kepler space telescope but to view a planet 4.2 light years from the Earth that would require a planet with a diameter of more than ten times the diameter of our solar system.

 

[phinds]

Do you have a question or did you just need to let us know about that?

 

[Bandersnatch]

The question seems to be: how is it possible to observe a planet when your instrument has insufficient resolution.

The answer lies in the technique used - the planets observed by Kepler are not directly resolved, but their presence is inferred from stellar light curves. That is, the CCD camera on the spacecraft collects light from a star, measuring its intensity. When a planet transits in front of the star, it obscures some of this light. The size and orbit of the planet can be determined from the depth and duration of the dip in luminosity (i.e. 'light curves').

More on the method can be found here:
http://kepler.arc.nasa.gov/Mission/QuickGuide/howKeplerFindsPlanets/

 

[sophiecentaur]

There is another technique. Kevin Apps, credited with finding the first exoplanet (Planet Kevin) told a group of my students that they used Doppler shift due to the Wobble, as a large planet orbits a star. I seem to remember that it required Jupiter sized planets.

 

[DrSteve]

To which physical point do you refer? The star-planet separation?

 

[sophiecentaur]

To which physical point do you refer? The star-planet separation?

The wobble in relative star/Earth velocity gives a measurable (apparently) shifting on wavelength (presumably of some sharp absorption lines).
Afair, his talk was given around ten years ago. I guess the method would have an advantage in that the effect would be detectable even without a transit of the planet. It always bothers me that we must be missing a significant number of planets that have orbits which don't present us with a transit.

 

[DrSteve]

The wobble in relative star/Earth velocity gives a measurable (apparently) shifting on wavelength (presumably of some sharp absorption lines).
Afair, his talk was given around ten years ago. I guess the method would have an advantage in that the effect would be detectable even without a transit of the planet. It always bothers me that we must be missing a significant number of planets that have orbits which don't present us with a transit.

I understand the Doopler shift method but still don't know which physical separation you refer to in your original post.

 

[sophiecentaur]

I understand the Doopler shift method but still don't know which physical separation you refer to in your original post.

?? The relevant measurement was of the change of relative velocity of the Star (the source) and the Earth (receiver). The variation in velocity (amplitude and frequency) and the 'known' mass of the star (from other data such as absolute magnitude and spectrum) would give the probable mass and orbital radius of the orbiting planet. He was well chuffed with himself about that - but then, so would anyone be. Thing was, he didn't invent the technique, he made a calculation to suggest the part of the galaxy in which to look. They looked . . . . and they found.

 

[DrSteve]

Then the .1 arcsec separation mentioned in the original post has no bearing on anything. Did you have a question that you wanted to pose to the forum?

 

[Bandersnatch]

DrSteve, you're confusing sophiecentaur with the OP, who has absconded.

 

[DrSteve]

DrSteve, you're confusing sophiecentaur with the OP, who has absconded.

Thanks much. Responding via my cell phone leaves much to be desired.

 

[sophiecentaur]

Thanks much. Responding via my cell phone leaves much to be desired.

So I'm not the only one. The small screen is like viewing the world through a toilet roll tube.
We already decided that resolution is just no enough. I wonder if it will ever be.

 

[DrSteve]

It's difficult, if not impossible, to get a sweeping overview of an online conversation from a phone, especially if a thread gets hijacked.

 

[sophiecentaur]

DrSteve, you're confusing sophiecentaur

That's not hard to do!

 

[Chronos]

Speckle interferometry can tease amazing details from an otherwise apparently random collection of photons.

 

[sophiecentaur]

Speckle interferometry can tease amazing details from an otherwise apparently random collection of photons.

Yes. Mr Shannon implies that, given time, there is no limit to the possible resolving power.