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In april 2002 the inner planets had aligned and this event was captured in this beautiful photo:

enter image description here

But, according to this website simulations for the date, Jupiter was pretty much away. Is that possible? Can Jupiter saw as a straight line even be so far from the other planets?

enter image description here

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  • $\begingroup$ I'm not 100% sure what you're asking, but, remember, we're viewing from the Earth, not the Sun. Does that help? $\endgroup$
    – user21
    Mar 5 '18 at 19:22
  • $\begingroup$ thanks, but not help. I'm asking why Jupiter is aside in the model, but in the picture looks like in a straight line. $\endgroup$
    – Max
    Mar 6 '18 at 3:03
  • $\begingroup$ In Solar System Live, try the Real orbit scale and a different heliocentric viewpoint. $\endgroup$
    – Mike G
    Mar 7 '18 at 16:42
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Below is an image of the solar system from that date. You can imagine drawing lines from the Earth to the various planets. You will see that Saturn, Mars, Venus and Mercury are quite closely aligned. And Jupiter is about 25 degrees out of that alignment. This matches with the photo that shows Jupiter further from the other planets.

enter image description here

Note that my image, derived from Nasa shows the orbits of the planets are not equally spaced. Your image does not represent reality.

The photo shows four planets quite close, and Jupiter a little way from them, just as the model of the solar system suggests. Of course the planets are in a straight line in the sky. They always are in a straight line, because they all are on the ecliptic. The alignment was significant because the planets appeared close together.

All the planets move around the sun in (almost) the same plane. The Earth also moves in this plane. The plane that the planets all move it is called the "plane of the ecliptic". Imagine a circle drawn on a piece of paper. If you look at the circle from above you see a circle. If you look at it from an angle you see an ellipse, and if you look at it from the side you only see a line. The Earth is in the same plane as the other planets, so all the planets appear to be moving in a line. This means that the positions of the planets in the sky will "always" be in a line, even when there is no alignment. The plane of the ecliptic looks like a line, because Earth is on the plane.

However when there is an alignment with the Earth (as there was in 2002) the planets will appear to be not only on the line of the ecliptic but close together in the sky.

Of course the planets are not actually close together, and there are no gravitational or other malevolent influence of planets being in a line

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  • $\begingroup$ Thanks, James. I understand Jupiter's 25º degrees, but in the picture I uploaded he looks like in a straight line like the others. This is a optical illusion? Caused by what? Roundness of earth? $\endgroup$
    – Max
    Mar 6 '18 at 3:02
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    $\begingroup$ This is the point that I make in last paragraph. I shall expand on it. $\endgroup$
    – James K
    Mar 6 '18 at 10:05
  • $\begingroup$ Max, if you draw a straight line through Mercury and Saturn in the photo, you'll see that Mars is very close to the line but Jupiter is not, it's far to the right. The photo is exactly consistent with the image @JamesK provided. There's no illusion. $\endgroup$ Mar 10 '18 at 11:32
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    $\begingroup$ @Chappo no. That's irrelevent.Jupiter is on the same line because they are all on the line of the ecliptic. Jupiter is far from the other planets in the sky because it is not in alignement with them $\endgroup$
    – James K
    Mar 10 '18 at 12:59
  • $\begingroup$ @JamesK, thanks for the clarification, I've done some further reading and can see I was confusing alignment with inclination. Regarding alignment: on that day, there was only 18º separating the four planets from Mercury to Saturn along the ecliptic, whereas Jupiter was a further 28º from Saturn. Regarding inclination, the ecliptic is of course an arc, and each planet's path is inclined at a different angle to the ecliptic, so it was much too simplistic of me to equate the ecliptic to "a straight line through Mercury and Saturn", especially when Mercury has the greatest inclination (over 7º). $\endgroup$ Mar 11 '18 at 2:55

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