Capturing a distant planet's light

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Discussion Overview

The discussion revolves around the methods astronomers use to analyze the light from distant planets, particularly focusing on how they can determine a planet's materials based on reflected light. The conversation touches on the challenges of isolating light from exoplanets amidst other light sources and the technologies employed to achieve this, including spectroscopic methods and adaptive optics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that astronomers can identify a planet's materials through the light that reflects back, but there are challenges in ensuring that only the light from the target planet is captured.
  • Others argue that while it is theoretically possible to analyze exoplanets' light, it is particularly difficult due to the brightness of the stars they orbit, which can overwhelm the signals from the planets.
  • A participant mentions that most spectroscopic data comes from transit planets, where the planet's atmosphere absorbs certain wavelengths, creating a detectable dip in the spectrum.
  • It is noted that direct imaging of large planets in wide orbits is feasible, and this can be done similarly to how stars are studied.
  • One participant shares a video about coronagraphs, which are tools that help in directly imaging exoplanets and analyzing their spectra.
  • Another participant discusses attending a lecture on optical technologies for exploring the Alpha Centauri system, highlighting advancements in adaptive optics.
  • There is mention of a growing number of resources available online regarding adaptive optics and exoplanet atmospheres.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and agreement on the methods used to analyze distant planets. While there is acknowledgment of the theoretical possibilities, the practical challenges and limitations remain a point of contention.

Contextual Notes

Participants indicate that the effectiveness of these methods may depend on specific conditions, such as the brightness of the star and the technology used, which are not fully resolved in the discussion.

Who May Find This Useful

This discussion may be of interest to those studying astronomy, particularly in the fields of exoplanet research, optical technologies, and spectroscopy.

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

 
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Drakkith said:
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 :)
 
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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. :frown:
 
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'.
 

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