5 ms·

A planet the size of the earth at the distance of proxima centauri is about 6.582⋅10^-5 arcseconds wide (a 20'000th of an arcsecond) angle(in degrees) = size /

by cnvogel 10y ago

A planet the size of the earth at the distance of proxima centauri is about 6.582⋅10^-5 arcseconds wide (a 20'000th of an arcsecond) angle(in degrees) = size / distance / pi ⋅ 180°, take times 3600 for arc seconds https://www.wolframalpha.com/input/?i=(diameter+of+the+earth)%2F(distance+to+proxima+centauri)+%2F+pi+*+180+*+3600 https://www.wolframalpha.com/input/?i=(diameter+of+the+earth... I didn't find a easy round number for James Webb, but Hubble's angular resolution is 1/10th of an arcsecond, at least a factor 2000 too low to even resolve the planet's disk as one pixel. https://www.spacetelescope.org/about/faq/ https://www.spacetelescope.org/about/faq/

dalke 10y ago
http://jwst.nasa.gov/faq_solarsystem.html#angularresolution http://jwst.nasa.gov/faq_solarsystem.html#angularresolution says: > The specification is that the telescope is diffraction limited at 2 μm, which means a Strehl ratio of 0.8 and a wavefront error of 150 nm rms. With a 6.5 m telescope, 1.22 λ/D = 0.077 arcsec at 2 μm. The smallest pixels (NIRCam 0.6-2.5 μm) are just 0.034 arcsec. But a lot of the wavefront error is due to imperfect alignment of the parts, and it's possible to do better for a small part of the field of view. A telescope can still detect something smaller than its resolution. We can see stars with our eyes, after all. Even astronauts in space, where there is no atmosphere to move the light around. Here are some of the best attempts at direct imaging with a telescope: http://www.planetary.org/explore/space-topics/exoplanets/direct-imaging.html http://www.planetary.org/explore/space-topics/exoplanets/dir... The problem is the planet is dim and close to a bright star. If this planet is 1 AU out, then there's a 0.77 arcsec between it and the the star, which would make it easier to distinguish the two.
- deleted 10y ago
  [deleted]
- dharma1 10y ago
  Quantum telescopes should get us beyond the diffraction limit http://arxiv.org/pdf/1508.04275v4.pdf http://arxiv.org/pdf/1508.04275v4.pdf

by cnvogel 10y ago

dalke 10y ago

http://jwst.nasa.gov/faq_solarsystem.html#angularresolution http://jwst.nasa.gov/faq_solarsystem.html#angularresolution says: > The specification is that the telescope is diffraction limited at 2 μm, which means a Strehl ratio of 0.8 and a wavefront error of 150 nm rms. With a 6.5 m telescope, 1.22 λ/D = 0.077 arcsec at 2 μm. The smallest pixels (NIRCam 0.6-2.5 μm) are just 0.034 arcsec. But a lot of the wavefront error is due to imperfect alignment of the parts, and it's possible to do better for a small part of the field of view. A telescope can still detect something smaller than its resolution. We can see stars with our eyes, after all. Even astronauts in space, where there is no atmosphere to move the light around. Here are some of the best attempts at direct imaging with a telescope: http://www.planetary.org/explore/space-topics/exoplanets/direct-imaging.html http://www.planetary.org/explore/space-topics/exoplanets/dir... The problem is the planet is dim and close to a bright star. If this planet is 1 AU out, then there's a 0.77 arcsec between it and the the star, which would make it easier to distinguish the two.

deleted 10y ago
[deleted]
dharma1 10y ago
Quantum telescopes should get us beyond the diffraction limit http://arxiv.org/pdf/1508.04275v4.pdf http://arxiv.org/pdf/1508.04275v4.pdf