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I read somewhere that sun's daily course and complete cycle is visible in the ecliptic belt by zodiac constellations.

I didn't understand what that means closest I could find online is: https://www.youtube.com/watch?v=x1DqwC7lRpk

Is the sun's route visible during the night in some areas? Can someone explain?

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  • $\begingroup$ @Chappo:Ah, so although the sun always rise from the exact same point through out the year at the same location but the visible stars around sunrise/sunset changed and within 1 calendar year the whole zodiac passed by? Did I get it right? Also does this depend on the location? I mean can you see the stars of the zodiac from any place on earth? $\endgroup$
    – Jim
    Dec 17, 2018 at 22:22
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    $\begingroup$ Jim, you might like to research "ecliptic" and "zodiac" on Wikipedia, and then edit your question to make it clearer what you need to know. The Sun does not rise from the same point each day - if it did, we wouldn't have seasons. You can see half of the zodiac on any clear night from any place on Earth. $\endgroup$ Dec 17, 2018 at 22:27
  • $\begingroup$ Yeah bad terminology from my side. Is it detectable that the sun traverses the whole zodiac within a year? $\endgroup$
    – Jim
    Dec 17, 2018 at 22:55

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The stars are not visible during the day, but they are still there (we just can't see them because of the brightness of the sun). We can't see the stars, but we can calculate where they would be if we could see them.

Over the course of the year the sun appears to move relative to the stars. This is actually due to the orbit of the Earth around the sun. The apparent motion of the sun is quite simple: it moves around the sky in a great circle, always following the same path, and taking exactly one year to complete. The route it takes is called the ecliptic. And most of the constellations that lie on the ecliptic are called the zodiac (they are very important to astrologers, but not especially important to astronomers).

The sun's route is not visible to the naked eye from Earth, but it can be calculated with great precision.

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  • $\begingroup$ Over the course of the year the sun appears to move relative to the stars. How is this noticed? Is it visible during the day somewhere? For a specific location the sun rises from the same point always right? So could you please elaborate on this? $\endgroup$
    – Jim
    Dec 17, 2018 at 21:32
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As the question is pointing out, because of Earth's thick atmosphere we have quite a bright sky, and so we can not easily see stars during the day. So how can we talk about the position of the Sun with respect to the stars if the stars around the Sun can't be seen?

Basic answer:

By using star charts, and the very steady and well known rotation speed of the Earth (360 degrees in about 23 hours, 56 minutes, 4 seconds) ancient (and modern) astronomers can calculate where the Sun is with respect to the stars. Before the invention of telescopes, astronomers had a huge amount of time on their hand with nothing better to do than these kinds of calculations, so they got quite good at it.

Practical answer:

After a century of measuring the positions of all the planets using both optical telescopes and radar reflection timings and round-trip signal delays from distant spacecraft, orbiters, and landers, and calculating masses and orbits to extremely high precision, the locations of the Sun and all the planets are known to a handful of kilometer accuracy. The Moon's position is known to centimeters!

With this, one can predict with computers where the Sun is with respect to the stars.


From space, in orbit above the Earth or in orbits around the Sun, spacecraft can indeed see the stars and the Sun at the same time! Even telescopes on balloons or aircraft high in the atmosphere can do this.

Here is a cool GIF I made of images taken by the SOHO spacecraft. You can see stars, comets, the planet Venus (the really bright object) very close to the Sun, and even the Pleiades pass over the top of the Sun!

From this answer:

These LASCO C3 images from SOHO were downloaded sohodata.nascom.nasa.gov/cgi-bin/data_query. The square frame is about 15.9 degrees wide.

enter image description here

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Celestial sphere

The diagram above shows the celestial sphere - an imaginary sphere with the Earth at its center (the sky all around the Earth). The equator of the Earth, projected onto the sky, therefore onto this sphere, is shown in green - the celestial equator. The plane of the Earth's orbit around the sun is the ecliptic. Note that the axis of the Earth is tilted with respect to the ecliptic.

Constellation map

Just like the surface of the Earth is divided into countries, seas and oceans, the celestial sphere is divided into the 88 official constellations defined by the international astronomical union. The above image shows the 88 constellations in the equirectangular map projection. 12 of these constellations are in the ecliptic region of the celestial sphere, and these are called the zodiacal constellations, because they are named as the signs in the zodiac, and were known to ancient civilizations, such as the Sumerians.

As the Earth orbits around the sun, the sun, as seen from Earth (see the SOHO probe animated image in the answer posted by uhoh), appears to cycle through all 12 zodiacal constellations each year. If we were in space, looking toward the sun, then we would see one of these 12 zodiacal constellations behind the sun. At the spring (vernal) equinox, the sun is between the Pisces and the Aquarius constellations. A month later, it is in Aries, and a month after that in Taurus, then Gemini, and so on.

See the grey band of zodiacal constellations in the map, showing the path of the sun (dotted line) in one year along the ecliptic, as seen from Earth.

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    $\begingroup$ As shown on the map you posted, the ecliptic passes through thirteen IAU constellations, not twelve. $\endgroup$
    – notovny
    Oct 3, 2023 at 15:45
  • $\begingroup$ @notovny True, Ophiucus crosses into Scorpius there. This map shows the current IAU constellation borders, which were defined so that any point in the sky is in the direction of one of the 88 constellations. Another thing is that the zodiacal constellations are not equal in size - eg Aries is much smaller than Virgo. To ancient civilizations, zodiacal constellations were a visualization for the division of the sun's path in 12 equal parts, because to them base 12, or base 60 (a multiple of 12) were significant, including for the Sumerians. $\endgroup$
    – jmarina
    Oct 4, 2023 at 6:21

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