How do scientists know so much about planets so far away?
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Most of the modern exoplanet discoveries are made using transit method.
Think of planets as moths who fly around their lamps (stars) very slowly, but at a constant speed and in circle. So you’re simply making a lot of photos of the star, some of them have a little bit darker dot due to a planet covering it. Then you combine photos and notice a pattern: the darkened dot appears regularly. This way you can get planet orbital period, its size, and some other characteristics. That doesn’t reveal all the planets though: only those which orbital plane faces Sun.
It would require very powerful telescope to take actual photo of that kind of planets, but I hope that JWST that it scheduled to be launched this year will make some progress here.
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