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Saturn and Jupiter will be low on the horizon in the near future?


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I read on the forum that Saturn and Jupiter will not be in particularly good positions for viewing in the northern hemisphere after a few years time and for many years after.

My question is this:

The planets orbit the sun, but how is it that the planets can rise differing amounts over the course of 20 years? Are all the planets in alignment with each other in a horizontal plane?

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The planets orbit the sun, but how is it that the planets can rise differing amounts over the course of 20 years? Are all the planets in alignment with each other in a horizontal plane?

Assuming I've understood you question properly ...

Yes the planets are all more or less in alignment in a horizontal plane. They all lie along or near the ecliptic. As jupiter takes about 12 years to orbit it will move from 23 deg south to 23 deg north in 6 years. Saturn takes about 30 years to orbit so will move from 23 deg south to 23 deg north in about 15 years. So right now Jupiter is in a good position for Northern hemisphere observers but Saturn is not. In 6 years Jupiter will be in a poor position for Norther hemisphere observers but Saturn will not have moved that much because of its much longer orbit.

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They are all approximately in the same plane but I think there is a difference of about 3 degree across all.

Jupiter is 1.3 degrees off, Saturn is about 2.5 off. As everything we measure is relative to the earth we count ourselves as 0, however we are at a 7 degrees off of the suns equater and Saturn is only 5.5, Jupiter is at 6 degrees to the suns equator.. So the earth could be more offset then a few others.

The ecliptic angles I suppose could be plus and minus, as in the planets oscillate across the ecliptic by (Saturn) +-2.5 degrees.

Not quite sure the best way to envisage the angle, either with reference to the ecliptic or to the suns equator.

The figures are from Wikipedia and again no indication whether the inclination is all one way or some up and some down.

Main reason they will be low is that their orbital period is long, so for a fair period we get closest at a similar time of the year, and the angle we are at, as in summer/winter, makes them low. As in we catch up with Jupiter for the next 4 years but it is always around the winter period when the sun (and so the ecliptic) is low and therefore the planets are low in the sky.

Not easy to explain in words. :crybaby2:

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Assuming I've understood you question properly ...

Yes the planets are all more or less in alignment in a horizontal plane. They all lie along or near the ecliptic. As jupiter takes about 12 years to orbit it will move from 23 deg south to 23 deg north in 6 years. Saturn takes about 30 years to orbit so will move from 23 deg south to 23 deg north in about 15 years. So right now Jupiter is in a good position for Northern hemisphere observers but Saturn is not. In 6 years Jupiter will be in a poor position for Norther hemisphere observers but Saturn will not have moved that much because of its much longer orbit.

Ah thanks for the explanations, I forgot to factor in the length of their orbits of the sun, it all makes sense now!! I was trying to work it out forgetting that they do not orbit as quickly as we do!!! Doh! :rolleyes: !

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No it wasn't explained well if it was mine, I realised what (I think it actually is) while soaking in a bath.

Realised that the angles they are to the ecliptic is of little relevance.

Using Jupiter, it has a orbit of 11 years.

We have an orbit of 1 year.

Assumption: We are at our closest position to Jupiter say in Janurary of Year 0

Next time we are at the closest we have gone round once but Jupiter has moved about 1/11 round, so we meet it at about 1 year and 1 month later in year 1.

So we meet up about a year and a month later each time.

In Jan the sun is low in the sky - our winter - as the ecliptic is the path of the sun and pretty closely the path of the planets they will also be low in the sky.

About 5 times round for us and half an orbit for Jupiter we are in our summer.

The Sun is high and so the ecliptic is high and therefore the planets are high.

Means that the high/low seperation is about half the orbit of the planet we are looking at.

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Ah thanks for the explanations, I forgot to factor in the length of their orbits of the sun, it all makes sense now!! I was trying to work it out forgetting that they do not orbit as quickly as we do!!! Doh! :rolleyes: !

Where's my Edit Post button gone?!!

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No it wasn't explained well.

Realised that the angles they are to the ecliptic is of little relevance.

Using Jupiter, it has a orbit of 11 years.

We have an orbit of 1 year.

Assumption: We are at our closest position to Jupiter say in Janurary of Year 0

Next time we are at the closest we have gone round once but Jupiter has moved about 1/11 round, so we meet it at about 1 year and 1 month later in year 1.

So we meet up about a year and a month later each time.

In Jan the sun is low in the sky - our winter - as the ecliptic is the path of the sun and pretty closely the path of the planets they will also be low in the sky.

About 5 times round for us and half an orbit for Jupiter we are in our summer.

The Sun is high and so the ecliptic is high and therefore the planets are high.

Means that the high/low seperation is about half the orbit of the planet we are looking at.

Oh I see *I think!*

I find it amazing that we can send probes to the planets even though everything in our solar system is moving and millions of miles apart!!

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