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james webb is going to characterize the

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atmospheres of exoplanets using a

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technique called transit spectroscopy if

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it's watching a planet transit across

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its star so the planet passes directly

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in front of its star from our point of

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view a really sensitive telescope can

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actually pick up those tiny tiny dips in

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the starlight and measure that a planet

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is there that's how we discovered a lot

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of the planets that we found planets

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have atmospheres and atmospheres can

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actually let some of the light pass

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through them on the way to our

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telescopes

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there are different gases in these

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atmospheres that can absorb different

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colors of light and so by using a really

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sensitive telescope that can measure

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what colors of light get absorbed when

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the planet is being backlit by its star

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and some of that light is passing

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through the atmospheres then we can

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learn what's in those atmospheres what

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gases are there that's absorbing those

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various colors of light what are they

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made of

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there's another technique called the

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phase curve technique the phase curve

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technique looks at the planet and the

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star when the planet is not in front of

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the star you got the signal from both

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and it also looks at them when the

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planet passes directly behind the star

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so in that case you can only see the

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signal from the star and by taking the

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difference of those two signals you can

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figure out what the signal from the

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planet was if you have a sufficiently

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sensitive instrument and from that

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technique we can also learn things about

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what the planet is made out of and also

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some interesting things about the

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planet's temperature and all this

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together tells us a lot of information

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about what these planets are like and