When looking at the night sky, the stars we can see just look like single dots. Are they alone in space- each one a single object? Or, when we look at a star, are we actually looking at a distant solar system within our galaxy?
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What we see from the Earth's surface with our eyes are just stars, any planets surrounding them - indeed, entire planetary systems are not visible by the naked eye.
That does not mean that there aren't any planets around those stars, the exoplanets listed in this European based Exoplanet catalogue were detected using much more precise and sophisticated means, listed on NASA's Years of Exoplanets page as:
- Doppler shift measurements
- Astrometric measurements
- Transit method
- Direct observation
- Gravitational Microlensing
The NASA page also describes why it is not possible to tell if a star has planets from observing with the naked eye:
The challenges of observing extrasolar planets stem from three basic facts:
- Planets don't produce any light of their own, except when young.
- They are an enormous distance from us.
- They are lost in the blinding glare of their parent stars.
Asides from stars, looking up with the naked eye, we may also be looking at galaxies, systems of stars etc. - these would be resolved using instruments, not really discernable with the naked eye.
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$\begingroup$ Actually, many of the dots in the night sky are themselves galaxies as well, not just single stars. In addition, most of the stars we can resolve with telescopes are in binary or multi-star systems, thus not alone. $\endgroup$ Oct 8, 2015 at 10:47
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$\begingroup$ Have added a bit about that in the answer. I was answering from the point of view of when the OP asked
he stars we can see just look like single dots. Are they alone in space- each one a single object? Or, when we look at a star, are we actually looking at a distant solar system within our galaxy?$\endgroup$– user94040Oct 8, 2015 at 10:53 -
$\begingroup$ Certainly the dots people see are not galaxies, just particularly bright and often quite nearby stars. One can see some diffuse galaxies with the naked eye, but only far away from cities (as in, most people on Earth have never been somewhere dark enough to see them). $\endgroup$– user10851Oct 8, 2015 at 15:10
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$\begingroup$ Thank you for all the input. I realize that it is impossible to see with the naked eye, but to imagine that there is so much more than just a star when we look up is just unreal! $\endgroup$ Oct 13, 2015 at 6:02
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$\begingroup$ Yes, that is a wonder of looking up at the night sky... is to wonder, then discover what we are actually looking at! $\endgroup$– user94040Oct 13, 2015 at 7:52