B Capturing a distant planet's light

[Greg Bernhardt]

Correct me if I'm wrong, but astronomers can tell a planet's materials by the light that reflects back? If that is the case for really far out planets like the ones that are Earth like, how can you be sure you're getting only the light from that planet into your device when I'm sure light is bouncing in from everywhere else.

 

[mfb]

Correct me if I'm wrong, but astronomers can tell a planet's materials by the light that reflects back?

Theoretically yes, but that is a very challenging approach for exoplanets (it is trivial for the bright and well-isolated planets in the solar system): The star is nearby and much brighter. Most spectroscopic data comes from transit planets: if they pass through our line of sight, the atmosphere absorbs some wavelengths, that produces a notable dip in the spectrum. No other object can lead to such a dip at the right time.

For a few large planets in large orbits direct imaging is possible: you study it like you would study a star.

In all cases, you need a good telescope to get light only from the target direction.

 

[Drakkith]

Hey Greg! Here's a neat video on how a coronograph helps us directly image exoplanets and see their spectrum.

 

[davenn]

Hey Greg! Here's a neat video on how a coronograph helps us directly image exoplanets and see their spectrum.

Thanks for that mate ... some new processing technology for me :)

 

[Drakkith]

On Thursday I attended the first half of a lecture on the optical technologies required to explore the Alpha Centauri system by Dr. Eduardo Bendek, whose "dissertation work resulted in the world’s first demonstration of Multi-Laser Ground Layer Adaptive Optics system", to quote the e-mail that was sent out announcing the lecture. He showed that video that I linked and explained how it worked. I enjoyed the lecture, but, unfortunately, I had to leave early to get in some homework that was due the next morning. That was then pushed back to midnight the next day after I had busted my butt completing it before Thursday ended...

I wish I could have stayed. He had just gotten into the meat of the lecture when I left.

 

[Bandersnatch]

There's been a plethora of videos, both public lectures and specialist colloquiums, on using adaptive optics and other techniques, popping up on youtube recently. Just search of 'exoplanet atmospheres'.