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Discovering a solar system that cannot be seen by the naked eye on earth seems like an easy task with telescopes (e.g. the hubble telescope). I'm guessing, that our sun is the reference point for the bearing of the telescope at the point of discovery of a solar system.

But how do you find this solar system again? F.e., after discovering a "new" solar system, a year passes by, and there is need to know in which "direction" this solar system is in relation to ours.

A bit off-topic, but a reason as to why this question might be important: In science fiction there is often the possibility to travel faster than light, reaching other solar system quickly - or for the sake of this question lets assume, we would be able to travel there too in a timely manner. How would they/we know where to go, since the universe is ever expanding.

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I think you're overestimating how quickly stars appear to move as viewed from Earth. Once a telescope like Kepler identifies a solar system around a star, we know where that star is. Stars have coordinates associated with them that astronomers can use to know where to point their telescopes to see it. For example, look at the star Betelgeuse. Look in the info box on the right, the right ascension and declination are the coordinates to find it. On the timescale of one Earth year, or even a few hundred Earth years, the stars are mostly fixed, and that coordinate to find them still works. Sure they move slightly, but not enough to lose track of it, or even enough to dramatically change how the constellations appear to us. Even if one does somehow move dramatically, it would take decades to centuries, and astronomers would be tracking it and updating the coordinate information.

Think about it this way. The constellations used in the sky today are named after many ancient Greek and Roman mythological characters. This isn't something we decided recently, they were named hundreds or thousands of years ago and they're still recognizable in the same form they were then. If stars moved across our sky as quickly as you appear to think, those constellations would all have to be renamed. You need timescales of tens of thousands of years to make the sky unrecognizable, and even then it would have more to do with the precession of the equinoxes.

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Newly found solar systems will be associated with stars. There is a well defined system of coordinates for stars (and other celestial objects). Stars, other than the sun, are so far away that their coordinates change only a very small amount from year to year, and so it is easy to locate them.

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  • $\begingroup$ how are these well defined system of coordinates for stars defined? Since the distances between solar systems is so vast, the slightest mistake in calculation of the bearing would result in an enormous error. (Given, that you couldn't adjust your course until you reach your destination) $\endgroup$ – Johannes Jul 3 '17 at 20:11
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    $\begingroup$ @Johannes about celestial coordinate systems, you should check out this Wikipedia page . $\endgroup$ – Cody Jul 3 '17 at 20:16
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    $\begingroup$ You don't need to worry about distance, just direction, to point a telescope in the right place. The coordinates that I referred to are latitude, defined relative to the plane of the Earth's equator, and longitude, which is defined relative to the Sun's position ata particular time. If you need more information search for right ascension and latitude. $\endgroup$ – Dr Chuck Jul 3 '17 at 20:18

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