6 ms·

Apparently finds are close enough to us that we should be able "to follow up, to see, for example with the James Webb Space Telescope that we're going to launch

by cletusw 10y ago

Apparently finds are close enough to us that we should be able "to follow up, to see, for example with the James Webb Space Telescope that we're going to launch [next] year, the atmospheres and also to look at bio-signatures, if there are any" !

twoodfin 10y ago
Optically? That's nuts! Anyone know how this would work? Can we really expect Webb to measure light diffraction/refraction through a few miles of atmosphere on a planet 40 ly away?
- semaphoreP 10y ago
  It'll be in the near-infrared, but the light won't be separated from the star. How they observe the atmosphere is that when the exoplanets transit, they block out different amounts of light at different wavelengths. From that, one can deduce an atmospheric spectrum.
  - mturmon 10y ago
    Absolutely right. Here is a recent paper on exoplanet atmosphere characterization by JWST: https://arxiv.org/abs/1511.05528 https://arxiv.org/abs/1511.05528 -- the overview is at https://jwst.nasa.gov/origins.html https://jwst.nasa.gov/origins.html As you say, the contrast between seeing (star + planet) during a transit, versus star alone, is enough to identify absorption of infrared light by some chemical species. The simulations in the above paper basically show they can infer some chemical abundances (carbon, oxygen) and some atmospheric parameters (inversion layers) for Neptunes and Jupiters. But probably not for Earths, so not for the system in the OP. Even for big, thick atmospheres, these spectroscopic characterizations take a lot of observation time (like, days). The race is indeed on to develop instruments and algorithms for this problem -- e.g., detecting CH4 or CO2 in an exo-Earth atmosphere. There's feverish activity in the Astronomy community around this, and post-JWST missions are being formulated to tackle the problem.
  - sand500 10y ago
    Would using a shield to block out the star be good enough to image the planets? https://en.m.wikipedia.org/wiki/New_Worlds_Mission https://en.m.wikipedia.org/wiki/New_Worlds_Mission
    - semaphoreP 10y ago
      It will depend on the size of the telescope, but for all practical purposes, these planets are too close to their star to see directly. A starshade will be good for Earth-like planets at Earth-like separations around Sun-like stars though.
    - mturmon 10y ago
      There are a lot of approaches. The Spitzer results in the OP here, and the JWST concept above, is about characterizing exoplanet atmospheres during a transit using spectroscopy. The concept you link is a "starshade". It's a sister concept to a "coronagraph" -- both use an occulting disk to block out the light from the host star, so that a non-transiting exoplanet can be observed. One goal is to image exoplanets directly, and another is to gather spectra for characterization. One of two current mission studies doing studies of the two approaches is HabEx (http://www.jpl.nasa.gov/habex/ http://www.jpl.nasa.gov/habex/). Obviously, the starshade is more complex/cumbersome/expensive. Using one method or another, you have to achieve a contrast of about 1e10 between the star and the exoplanet. For every 1e10 photons that come in from the host star, your starshade/coronagraph has to let at most one get through to the detector.
kitrose 10y ago
Can someone explain to me why we don't replicate some of these key platforms like the Hubble and James Webb ST? It seems like the major limitation for discovery is getting enough observation time for whatever certain point in the sky that scientists are researching. Why don't we launch a second copy of James Webb?
- pwython 10y ago
  A Hubble or James Webb is easily a billion dollar effort, making it THE major limitation for discovery. No one is investing that sort of money for no return. Honestly, even if they did, it would be frowned upon considering the more important humanitarian investments at hand.
  - thangalin 10y ago
    "In 1970, a Zambia-based nun named Sister Mary Jucunda wrote to Dr. Ernst Stuhlinger, then-associate director of science at NASA's Marshall Space Flight Center, in response to his ongoing research into a piloted mission to Mars. Specifically, she asked how he could suggest spending billions of dollars on such a project at a time when so many children were starving on Earth." I encourage you to read his reply. http://www.lettersofnote.com/2012/08/why-explore-space.html http://www.lettersofnote.com/2012/08/why-explore-space.html
    - a_imho 10y ago
      The voyage to Mars will certainly not be a direct source of food for the hungry. However, it will lead to so many new technologies and capabilities that the spin-offs from this project alone will be worth many times the cost of its implementation. Supposedly he is right and NASA money is well spent, it still not implies it is efficiently spent. Furthermore, he seems to writes off aids as a net loss in his analogy, without considering the benefits of children not starving (to death). Which is especially weird with the follow up We need more young men and women who choose science as a career /devils advocate
- RileyJames 10y ago

by cletusw 10y ago

twoodfin 10y ago

Optically? That's nuts! Anyone know how this would work? Can we really expect Webb to measure light diffraction/refraction through a few miles of atmosphere on a planet 40 ly away?

semaphoreP 10y ago
It'll be in the near-infrared, but the light won't be separated from the star. How they observe the atmosphere is that when the exoplanets transit, they block out different amounts of light at different wavelengths. From that, one can deduce an atmospheric spectrum.
- mturmon 10y ago
  Absolutely right. Here is a recent paper on exoplanet atmosphere characterization by JWST: https://arxiv.org/abs/1511.05528 https://arxiv.org/abs/1511.05528 -- the overview is at https://jwst.nasa.gov/origins.html https://jwst.nasa.gov/origins.html As you say, the contrast between seeing (star + planet) during a transit, versus star alone, is enough to identify absorption of infrared light by some chemical species. The simulations in the above paper basically show they can infer some chemical abundances (carbon, oxygen) and some atmospheric parameters (inversion layers) for Neptunes and Jupiters. But probably not for Earths, so not for the system in the OP. Even for big, thick atmospheres, these spectroscopic characterizations take a lot of observation time (like, days). The race is indeed on to develop instruments and algorithms for this problem -- e.g., detecting CH4 or CO2 in an exo-Earth atmosphere. There's feverish activity in the Astronomy community around this, and post-JWST missions are being formulated to tackle the problem.
- sand500 10y ago
  Would using a shield to block out the star be good enough to image the planets? https://en.m.wikipedia.org/wiki/New_Worlds_Mission https://en.m.wikipedia.org/wiki/New_Worlds_Mission
  - semaphoreP 10y ago
    It will depend on the size of the telescope, but for all practical purposes, these planets are too close to their star to see directly. A starshade will be good for Earth-like planets at Earth-like separations around Sun-like stars though.
  - mturmon 10y ago
    There are a lot of approaches. The Spitzer results in the OP here, and the JWST concept above, is about characterizing exoplanet atmospheres during a transit using spectroscopy. The concept you link is a "starshade". It's a sister concept to a "coronagraph" -- both use an occulting disk to block out the light from the host star, so that a non-transiting exoplanet can be observed. One goal is to image exoplanets directly, and another is to gather spectra for characterization. One of two current mission studies doing studies of the two approaches is HabEx (http://www.jpl.nasa.gov/habex/ http://www.jpl.nasa.gov/habex/). Obviously, the starshade is more complex/cumbersome/expensive. Using one method or another, you have to achieve a contrast of about 1e10 between the star and the exoplanet. For every 1e10 photons that come in from the host star, your starshade/coronagraph has to let at most one get through to the detector.

kitrose 10y ago

Can someone explain to me why we don't replicate some of these key platforms like the Hubble and James Webb ST? It seems like the major limitation for discovery is getting enough observation time for whatever certain point in the sky that scientists are researching. Why don't we launch a second copy of James Webb?

pwython 10y ago
A Hubble or James Webb is easily a billion dollar effort, making it THE major limitation for discovery. No one is investing that sort of money for no return. Honestly, even if they did, it would be frowned upon considering the more important humanitarian investments at hand.
- thangalin 10y ago
  "In 1970, a Zambia-based nun named Sister Mary Jucunda wrote to Dr. Ernst Stuhlinger, then-associate director of science at NASA's Marshall Space Flight Center, in response to his ongoing research into a piloted mission to Mars. Specifically, she asked how he could suggest spending billions of dollars on such a project at a time when so many children were starving on Earth." I encourage you to read his reply. http://www.lettersofnote.com/2012/08/why-explore-space.html http://www.lettersofnote.com/2012/08/why-explore-space.html
  - a_imho 10y ago
    The voyage to Mars will certainly not be a direct source of food for the hungry. However, it will lead to so many new technologies and capabilities that the spin-offs from this project alone will be worth many times the cost of its implementation. Supposedly he is right and NASA money is well spent, it still not implies it is efficiently spent. Furthermore, he seems to writes off aids as a net loss in his analogy, without considering the benefits of children not starving (to death). Which is especially weird with the follow up We need more young men and women who choose science as a career /devils advocate
RileyJames 10y ago