Nasa news life on other planets7/24/2023 ![]() Webb actually complements NASA's other solar system missions, including those observatories on the ground, orbiting Earth, and in deep space. In addition to studying planets outside our solar system, scientists want to learn more about our own home. ![]() The ultimate goal, of course, is to find a planet with a similar atmosphere to that of Earth. ![]() Why is an infrared telescope key to characterizing the atmospheres of these exoplanets? The benefit of making infrared observations is that it is at infrared wavelengths that molecules in the atmospheres of exoplanets have the largest number of spectral features. This is because different elements and molecules absorb light at characteristic energies and this is how we know where in a spectrum we might expect to see the signature of sodium (or methane or water) if it is present. If, for example, the planet has sodium in its atmosphere, the spectrum of the star, added to that of the planet, will have what we call an "absorption line" in the place in the spectra where would expect to see sodium (see graphic below). When a planet passes in front of a star, the starlight passes through the planet's atmosphere. The graphical representations of these measurements are called spectra, and they are the key to unlocking the composition of exoplanet atmospheres. Spectroscopy is simply the science of measuring the intensity of light at different wavelengths. The presence of sodium in the atmosphere of Hot Jupiter exoplanet HD 209458 is measured by studying its spectrum. That includes its color, differences between winter and summer, vegetation, rotation, weather.How is this done? The answer again is spectroscopy. The image of an exoplanet would just be a spot, not a grand panorama, but by studying that spot, we can learn a great deal about it. Webb also carries coronagraphs to enable direct imaging of exoplanets near bright stars. (Astronomers call this a "transit".) Collaboration with ground-based telescopes can help us measure the mass of the planets, via the radial velocity technique (i.e., measuring the stellar wobble produced by the gravitational tug of a planet), and then Webb will do spectroscopy of the planet's atmosphere. One method Webb is using for studying exoplanets is the transit method, which means it looks for dimming of the light from a star as its planet passes between us and the star. How is this good for studying exoplanets? One of the main uses of the James Webb Space Telescope is to study the atmospheres of exoplanets, to search for the building blocks of life elsewhere in the universe. (See JPL's Planetquest website for the latest discoveries.) Since then we have found thousands of exoplanets (and in every sort of star system imaginable), and we continue to narrow in on smaller and more earth-like planets. The first solar system found outside our own did not involve a main sequence star like our own, but a pulsar. An artist's conception of PSR B1257+12's system of planets which does not involve a main sequence star like our own, but rather, a pulsar.
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