4 ms·

I wonder if the James Webb Space Telescope will be able to image it since it's so close.

danpalmer 10y ago
Can anyone "do the maths" on this. I don't feel well enough equipped, but I'd love to know the feasibility of this, or what we would be able to image if anything.
- 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
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    - 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
teamonkey 10y ago
"Webb's angular resolution, or sharpness of vision, will be the same as Hubble's, but in the near infrared. This means that Webb images will appear just as sharp as Hubble's do. Webb will have an angular resolution of somewhat better than 0.1 arc-seconds at a wavelength of 2 micrometers (one degree = 60 arc-minutes = 3600 arc-seconds). Seeing at a resolution of 0.1 arc-second means that Webb could see details the size of a US penny at a distance of about 24 miles (40 km), or a regulation soccer ball at a distance of 340 miles (550 km)." http://jwst.nasa.gov/faq.html#sharp http://jwst.nasa.gov/faq.html#sharp
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throwaway_yy2Di 10y ago
I don't think JWST could even resolve it from its parent star, judging by [0]. They're too close together. Proxima Centauri has a luminosity of 0.0017 suns [1], so Earth-like conditions would occur at ~sqrt(0.0017) au = 0.04 au, an apparent angular separation of arcsin(0.04 au / 4.2 light years) = 0.03". JWST wants star-planet separations at least an order of magnitude larger [0], ideally with very hot, infrared-bright planets. E-ELT should be able to resolve them, according to [2]. Page 7 gives values for a very similar scenario: an Earth-like planet around an M dwarf (like Proxima), 6 pc away (5 times farther), at an angular separation of 0.015" (half as wide). In this scenario, E-ELT could image the star and planet as separate points, and take useful spectroscopic measurements of the planet's light. For it example it could detect a spectral line of oxygen (O2) in 4 hours of exposure time. [0] http://nexsci.caltech.edu/workshop/2016/NIRCam_Planets_and_BDs_Sagan2.pdf http://nexsci.caltech.edu/workshop/2016/NIRCam_Planets_and_B... [1] https://en.wikipedia.org/wiki/Proxima_Centauri https://en.wikipedia.org/wiki/Proxima_Centauri [2] https://www.eso.org/sci/meetings/2014/exoelt2014/presentations/Kasper.pdf https://www.eso.org/sci/meetings/2014/exoelt2014/presentatio...

Can anyone "do the maths" on this. I don't feel well enough equipped, but I'd love to know the feasibility of this, or what we would be able to image if anything.

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

teamonkey 10y ago

"Webb's angular resolution, or sharpness of vision, will be the same as Hubble's, but in the near infrared. This means that Webb images will appear just as sharp as Hubble's do. Webb will have an angular resolution of somewhat better than 0.1 arc-seconds at a wavelength of 2 micrometers (one degree = 60 arc-minutes = 3600 arc-seconds). Seeing at a resolution of 0.1 arc-second means that Webb could see details the size of a US penny at a distance of about 24 miles (40 km), or a regulation soccer ball at a distance of 340 miles (550 km)." http://jwst.nasa.gov/faq.html#sharp http://jwst.nasa.gov/faq.html#sharp

deleted 10y ago

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throwaway_yy2Di 10y ago

I don't think JWST could even resolve it from its parent star, judging by [0]. They're too close together. Proxima Centauri has a luminosity of 0.0017 suns [1], so Earth-like conditions would occur at ~sqrt(0.0017) au = 0.04 au, an apparent angular separation of arcsin(0.04 au / 4.2 light years) = 0.03". JWST wants star-planet separations at least an order of magnitude larger [0], ideally with very hot, infrared-bright planets. E-ELT should be able to resolve them, according to [2]. Page 7 gives values for a very similar scenario: an Earth-like planet around an M dwarf (like Proxima), 6 pc away (5 times farther), at an angular separation of 0.015" (half as wide). In this scenario, E-ELT could image the star and planet as separate points, and take useful spectroscopic measurements of the planet's light. For it example it could detect a spectral line of oxygen (O2) in 4 hours of exposure time. [0] http://nexsci.caltech.edu/workshop/2016/NIRCam_Planets_and_BDs_Sagan2.pdf http://nexsci.caltech.edu/workshop/2016/NIRCam_Planets_and_B... [1] https://en.wikipedia.org/wiki/Proxima_Centauri https://en.wikipedia.org/wiki/Proxima_Centauri [2] https://www.eso.org/sci/meetings/2014/exoelt2014/presentations/Kasper.pdf https://www.eso.org/sci/meetings/2014/exoelt2014/presentatio...