If planets & the earth revolve around the sun, and the sun is a star like so many we see, are there any other stars that have planets revolving around them

Asker: Maurice, 40 years old

Answer

Yes, it certainly is.
In the meantime, about 500 so-called exoplanets are known around other stars. These are usually very massive planets, such as our Jupiter, that also orbit very close to their star.
These two properties are a result of the observation methods that very selectively favor the detection of these types of planets;

The two main methods of observation are:

– star cover
the planet passes between the star and the earth. This temporarily covers the star, making it slightly less bright. This effect is greatest on a large planet (because it obscures a larger portion of the star), and is most noticeable when the planet is very close to the star. After all, this means that the occultation occurs every few days, and not every few years as would a planet that is distant like Jupiter or Saturn. If aliens wanted to discover our own Jupiter that way, they would have to look at our sun continuously for at least 12 years, only to see the sun’s brightness decrease by about 1 percent for just a few hours or days. And, of course, they would have to observe another 12 years to be able to measure one period of Jupiter. For Saturn this would even be 2x 30 years. The disadvantage of this method is the need for the Earth to be exactly in the orbital plane of the planet.

– Doppler shift
Due to the presence of a heavy planet, the star itself will also perform a small circular motion, of which we can measure the periodic variation in speed. Again, a heavy planet will make the star move more. For example, Jupiter alone is able to make the sun make a circular motion with a radius of about 700,000 km. However, the effect of the earth is negligible. So here too the detection of heavy planets is favored. Again, the measurable effect is greater if the Earth is closer to or in the orbital plane of the planet. If the earth is perpendicular to it, the effect is zero.

The fact that we still know very few exoplanets with a mass like Earth does not mean that there are none. They’re just really hard to spot with current techniques.
You can find lists of the observed exoplanets on the internet. See for example:
http://exoplanet.eu/catalog.php

If planets & the earth revolve around the sun, and the sun is a star like so many we see, are there any other stars that have planets revolving around them

Answered by

prof.dr. Paul Hellings

Department of Mathematics, Fac. IIW, KU Leuven

Catholic University of Leuven
Old Market 13 3000 Leuven
https://www.kuleuven.be/

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