Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Pseudoscience-is-malarkey on 23/09/2022 15:06:27
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The fact that we cannot get very clear images via telescope of planets in our own solar system makes me feel that such a feat won't be accomplished until all of us on this forum have gone to our graves.
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No.
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The image resolution you can achieve depends on the wavelength you use, and the size of your telescope.
- For a planet far from the star, you would need to rely on infra-red radiation which has a long wavelength
- For a distant object, it subtends a small angle, so you need a very large telescope
- To image an exoplanet, you need a telescope thousands of kilometers across
See equations here: https://en.wikipedia.org/wiki/Optical_resolution#Lateral_resolution
For planets close to the star, there is some visible light - but the star puts out far more light than the planet, which swamps light from the planet. A device called a coronagraph can block out light from the star, leaving light from the planet. JWST has a cornonagraph, and has released some images of a planet far from its star - it just lights up a pixel or two (ie not enough to form an image).
https://en.wikipedia.org/wiki/Coronagraph
There are still some useful things you can do without forming an image:
- If you measure the Doppler shift of the star very accurately, you can often detect planets
- By seeing the orbital period of the planet, you can "weigh" the star, and tell a lot about the sunlight falling on the planet
- For planets which pass in front of the star, you can look at the spectrum of light filtered through the planet's atmosphere. JWST has released a spectrum from such a planetary transit.